Patent Application
20250221629
Devices, systems, and methods herein relate to a sensor that may be used to measure a parameter, including but not limited to pressure.
Sensors may be configured to measure various physical properties. For example, Wheatstone bridge sensors may include a piezoresistive circuit on a silicon-based die and may be configured as a pressure sensor or a strain gauge. However, piezoresistive sensor measurements are subject to an inherent resistor offset and inherent temperature offset that may be mitigated by an offset compensation circuit that may comprise one or more of a differential amplifier, potentiometer, Digital-to-Analog Converter (DAC), Analog-to-Digital Converter (ADC), resistors, and the like. Furthermore, the wires coupling the sensor to an electronic circuit may have a length (e.g., 500 mm or more) that functions as an antenna that picks up common mode noise. A differential low-pass filter and a differential amplifier may be used to provide high common-mode rejection for the wires. The circuits needed to compensate for sensor offsets and wire noise increases the cost, size, weight, and manufacturing complexity of a sensor. Accordingly, additional devices, systems, and methods of measuring a parameter may be desirable.
Described here are systems, devices, and methods including a sensor useful for measuring one or more parameters (e.g., physical properties) including, but not limited to, pressure (e.g., blood pressure). In some variations, the sensor may be part of a device that controls blood flow, for example, as one or more of a sensor proximal to an expandable member (e.g., balloon), a sensor distal to an expandable member, and a sensor within an expandable member. In these variations, the sensor may be very small and thin, as described further below. In other variations, the sensor may be included in a device that measures pressure (e.g., blood pressure) without controlling blood flow. One or more sensors may be used to measure the one or more parameters. For example, a plurality of sensors (e.g., two, three, four or more) may be used to measure the same parameter, each of a plurality of sensors may be used to measure different parameters, or a plurality of sensors may be employed where some of the plurality of sensors may be used to measure the same parameter and some of the plurality of sensors may be used to measure different parameters. Each sensor may be contained within its own sensor housing, or a plurality of sensors may be contained within a single sensor housing. In some variations, the sensor housing containing one or more sensors may be integrated into an elongate body (e.g., catheter) as described in more detail herein. In one variation, the sensor may comprise a first circuit configured to receive an input clock signal and output a first output clock signal having a predetermined ratio between the input clock signal and the first output clock signal using an adjustable delay, a second circuit configured to receive the input clock signal and output a second output clock signal using the adjustable delay, and a third circuit coupled to the first circuit and the second circuit, the third circuit configured to generate a third signal based on a difference between the first output clock signal and the second output clock signal.
In some variations, the first output clock signal may vary based on a first set of parameters and the second output clock signal may vary based on a second set of parameters different from the first set of parameters. In some of these variations, the first set of parameters may comprise one or more of temperature and voltage. In some of these variations, the second set of parameters may comprise temperature, voltage, and one or more of force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction.
In some variations, the third signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude. In some variations, a frequency of the first output clock signal and the second output clock signal may be each greater than a frequency of the input clock signal. In some variations, the first circuit may comprise a first plurality of delay circuits arranged in a ring configuration. In some of these variations, the first plurality of delay circuits may comprise a first plurality of inverter circuits and a first adjustable delay circuit. In some of these variations, the first adjustable delay circuit may comprise a rate counter. In some of these variations, the first plurality of inverter circuits may be coupled to a first multiplexer. In some of these variations, the first plurality of inverter circuits may be configured in a closed loop with positive feedback.
In some variations, the first delay circuit may comprise a first resistor-capacitor delay circuit. In some variations, the second circuit may comprise one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit. In some variations, the first circuit may comprise a first oscillator circuit.
In some variations, a fourth circuit may be coupled to the third circuit, the fourth configured to receive the input clock signal and output a fourth output clock signal using the adjustable delay. The third circuit may be configured to generate a fifth signal based on a difference between the first output clock signal and the fourth output clock signal. In some of these variations, the fifth signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.
In some variations, a substrate may comprise the first circuit, the second circuit, and the third circuit. In some variations, a first substrate may comprise one of the first circuit and the second circuit, and a second substrate may comprise the other of the first circuit and the second circuit.
In some variations, a fourth circuit may be configured to output the third signal as a digital signal. In some variations, a fourth circuit may be configured to output the third signal as a set of binary encoded bits at a periodic rate. In some variations, the fourth circuit may comprise one or more of a wire and an antenna.
Also described here are methods of measuring a parameter comprising receiving an input clock signal, generating a first output clock signal having a predetermined ratio between the input clock signal and the first output clock signal using an adjustable delay, generating a second output clock signal using the adjustable delay, and generating a third signal based on a difference between the first output clock signal and the second output clock signal.
In some variations, the first output clock signal may vary based on a first set of parameters and the second output clock signal may vary based on a second set of parameters different from the first set of parameters. In some variations, the first set of parameters may comprise one or more of temperature and voltage. In some variations, the second set of parameters may comprise temperature, voltage, and one or more of force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction.
In some variations, the third signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude. In some variations, a frequency of the first output clock signal and the second output clock signal may be each greater than a frequency of the input clock signal.
In some variations, a fourth output clock signal may be generated using the adjustable delay, and a fifth signal may be generated based on a difference between the first output clock signal and the fourth output clock signal. In some variations, the fifth signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.
In some variations, the third signal may be output as a digital signal. In some variations, the third signal may be output as a set of binary encoded bits at a periodic rate.
Also described herein is a sensor including a first ring oscillator circuit oscillating at a first oscillation rate. The first oscillation rate may be based on a first set of physical parameters and a second physical parameter. The sensor may further include a second ring oscillator circuit oscillating at a second oscillation rate. The second oscillation rate may be based on the first of physical parameters but not the second physical parameter. The sensor may further include a first rate counter circuit operatively coupled to the first ring oscillator circuit and configured to count a first number of oscillations at the first ring oscillator circuit during a sample period. The sensor may further include a second rate counter circuit operatively coupled to the second ring oscillator circuit and configured to count a second number of oscillations at the second ring oscillator circuit during the sample period. The sensor may further include circuitry configured to receive representations of the first number of oscillations and the second number of oscillations, and generate a value associated with the second physical parameter at the sensor based on the first number of oscillations and the second number of oscillations in response to receiving the representations of the first number of oscillations and the second number of oscillations.
In some instances, the sensor may be configured as described above and may further include communication circuitry. The communication circuitry may be configured to send representations of the first number of oscillations and the second number of oscillations to processing circuitry operatively coupled to the communication circuitry to cause the processing circuitry to generate a value associated the second physical parameter at the sensor. The generated value may be based on the first number of oscillations and the second number of oscillations in response to receiving the representations of the first number of oscillations and the second number of oscillations form the communication circuitry.
Some variations of the sensors configured to measure physical properties may generate a first output count signal using a first oscillating ring circuit of the sensor having a first oscillation rate, where the first oscillation rate may be modulated by an electrical parameter of a membrane of a MEMS subassembly of the sensor. A first value for the physical property may be determined based on the first output count signal. A second output count signal may be generated using a second oscillating ring circuit having a second oscillation rate that is independent of the physical parameter. A correction value may be determined based on the second output count signal. A measured value for the physical property may then be determined based on the first value and the correction value.
Also described herein is a method that includes obtaining a first count number indicating a number of oscillations at a first ring oscillator circuit during a sample period. The first ring oscillator circuit may be associated with a sensing membrane and oscillate at a first oscillation rate. The first oscillation rate may be based on a first set of physical parameters and a second physical parameter. The method may further include obtaining a second count number indicating a number of oscillations at a second ring oscillator circuit during the sample period. The second ring oscillator circuit may be associated with the sensing membrane and oscillate at a second oscillation rate. The second oscillation rate may be based on the first of physical parameters and independent of the second physical parameter. The method may further include determining a value associated with the second physical parameter at a sensor based on the first count number and the second count number.
Also described herein is a method that may include measuring a first value for a first parameter using a first sensor, sending the first value to a second sensor coupled to the first sensor, and measuring a second value for a second parameter using the second sensor. The method may further include producing a serial value that includes the first value and the second value.
Sensors (sensor assemblies) including a MEMS subassembly (e.g., a piezoresistive MEMS subassembly) are also described herein. In these variations, the sensors may generally include a substrate and a piezoresistive MEMS subassembly coupled to the substrate. The piezoresistive MEMS subassembly may include a membrane and a wall surrounding a measuring portion of the membrane. The wall may be configured to form a cavity between the membrane and the substrate, which may provide room for deflection (or deformation) of the membrane. In some variations, the measuring portion of the membrane may be configured to deflect in response to an externally applied pressure, e.g., blood pressure. The piezoresistive MEMS subassembly may also (optionally) include a reference portion, which may be a reference portion of the membrane.
The membrane may comprise silicon (e.g., single crystal silicon) and may have a thickness between about 1.0 micron to about 10 microns, including all values and sub-ranges therein. For example, the membrane may have a thickness of about 1.0 micron. The wall of the piezoresistive MEMS subassembly may form a continuous border on a first surface of the membrane and surrounding the measuring portion of the membrane. The border may have any suitable shape, e.g., rectangular, square, circular, ovular, or triangular. In some variations, the wall may be configured as a rectangularly shaped border surrounding the measuring portion. The height of the wall may be between about 5.0 microns and about 20 microns, including all values and sub-ranges therein. For example, the height of the wall may be about 10 microns.
To help maintain a robust cavity seal (i.e., a tight seal) between the wall and the substrate when conductors extend beyond the wall, at least one conductor may be embedded within the membrane. The at least one conductor may include a portion of the membrane that is heavily doped (e.g., contains a high concentration of phosphorus). In this instance, a part of the measuring portion of the membrane may be lightly doped.
At least a part of a top surface of the measuring portion of the membrane may be configured to reduce blood clot formation thereon. In one variation, the membrane may have one or more properties configured to reduce blood clot formation thereon. The one or more properties may be one or more of a surface roughness, hydrophilicity, hydrophobicity, and surface charge of the membrane. For example, the top surface may include a plurality of pillars or other surface structures that increase the hydrophobicity of the membrane. When pillars are used, the pillars may be made from polysilicon. In some variations, the pillars may have a height between about 5.0 microns to about 20 microns, including all values and sub-ranges therein. For example, the height of the pillars may be about 10 microns. In another variation, the membrane may include a coating or layer that prevents adhesion and/or proliferation of red blood cells and/or other blood components.
The substrate may be coupled to the piezoresistive MEMS subassembly using various bonding techniques. For example, the bond may be formed with or without annealing at an elevated temperature. The combined thickness of the substrate and the piezoresistive MEMS subassembly may be between about 100 microns and about 140 microns, including all values and sub-ranges therein. For example, the combined thickness of the substrate and the piezoresistive MEMS subassembly may be about 135 microns.
The substrate may include CMOS (complementary metal-oxide semiconductor) circuitry. The CMOS circuitry may include one or more oscillating rings, latches, counters, and/or serializers. In some variations, the substrate may include a first oscillating ring circuit having a first oscillation rate modulated by an electrical parameter of the measuring portion configured to generate a first output count signal, and a second oscillating ring circuit having a second oscillation rate modulated by the electrical parameter of a reference portion of the membrane configured to generate a second output count signal. A processor coupled to at least the substrate may be configured to determine a first parameter value based on the first output count signal and a second parameter value based on the second output count signal. The processor may be further configured to use the first parameter value and the second parameter value to determine a third (e.g., corrected) parameter value, which may be used to adjust expansion of an expanded member. The parameter values (first, second, third) may be any of a variety of parameters of interest, including but not limited to, pressure, pH, or an analyte level such as oxygen level, carbon dioxide level, lactate level. The third parameter value may be used to adjust expansion of an expandable member. In some variations, the expandable member may be a balloon of a blood flow control device. As previously mentioned, the measuring portion of the membrane may be configured to deflect in response to an externally applied pressure such as blood pressure. To prevent damage to the membrane due to over deflection, the top surface of the substrate may be configured as a membrane stop that limits deflection of the membrane within the cavity. In other variations, the substrate may include a trough configured to limit deflection of the membrane within the cavity.
The sensors described herein may also include one or more standoffs extending from the membrane (e.g., away from the cavity) configured to prevent damage to, or contamination of, the measuring portion of the membrane. The height of the one or more standoffs may be between about 20 μm to about 50 μm, including all values and sub-ranges therein. For example, the height of the one or more standoffs may be about 30 microns. When the wall is configured as a rectangularly shaped border, the sensor assembly may include four standoffs, where each standoff may be located at each corner of the border. The one or more standoffs may be made by a lithographic process, e.g., etching, and thus may comprise the same substrate material as the piezoresistive MEMS subassembly (e.g., silicon).
The sensors described herein may further include one or more wire guides configured to align one or more wires extending therefrom parallel to a surface of the sensor assembly. The one or more wire guides may be configured to receive an end of the one or more wires, and electrically couple the end to circuitry within the substrate. The one or more wire guides may include a slot or channel formed in any part (e.g., top, bottom, and/or side) of the substrate. In one variation, the sensor assembly comprises four wire guides. In another variation, the one or more wire guides may be formed in (e.g., by etching) a non-measuring portion of the membrane.
Methods for measuring a parameter using the sensors including a piezoresistive MEMS subassembly are also described herein. The methods may generally include generating a first output count signal using a first oscillating ring circuit having a first oscillation rate at a measuring portion of a membrane of a piezoresistive MEMS subassembly, and generating a second output count signal using a second oscillating ring circuit having a second oscillation rate. The methods may further include determining a parameter based on the first output count signal and the second output count signal. The membrane may further include a reference portion, and the second oscillating rate may be measured at the reference portion, though in other variations the reference portion is not used.
In some variations of the method, the first oscillation rate may be based on an amount of deflection of the measuring portion of the membrane, and the first oscillation rate may be used to determine a parameter. For example, the first oscillation rate may be used to determine pressure, e.g., blood pressure. In one variation, the parameter may be used to adjust expansion of an expandable member, e.g., a balloon, of a blood flow control device.
Devices configured to monitor a physiologic condition or adjust a parameter (e.g., blood flow or blood pressure) of a patient are also described herein. These devices may include any one or more of the sensors described herein integrated into an elongate body (e.g., a catheter). In some variations, the one or more sensors may be configured to measure blood pressure. In other variations, the one or more sensors may be configured to measure pH, and/or an analyte level, such as, for example, a lactate level, an oxygen level, and/or a carbon dioxide level. When the sensor(s) are included in a blood flow control device, a balloon may be coupled to the elongate body and configured for placement within a blood vessel. The one or more sensors may be contained within a sensor housing, which may protect the sensor(s) from damage due to body fluids (e.g., blood) or pressurization from the balloon of a blood flow control device. The sensor housing may be formed from any suitable material, e.g., a polymer, metal, or a metal alloy. In some variations, the sensor housing is made from stainless steel.
Additionally, devices configured to monitor a parameter are also described herein. The devices may include any one or more of the sensors described herein that measure a parameter (e.g., pressure (such as blood pressure), pH, or an analyte level such as oxygen level, carbon dioxide level, lactate level) integrated into an elongate body (e.g., a catheter). The one or more sensors may be contained within a sensor housing to help protect the sensor(s) from damage due to body fluids (e.g., blood) or other external factors. In some variations, the sensor and/or the sensor housing may be tubular in shape, and have a diameter of about 1 Fr. When the sensor is coupled to a PCBA (printed circuit board assembly) housing, the housing may include an adhesive configured to attach the PCBA housing to the skin of a patient. The adhesive in some instances may be provided as an adhesive patch.
Described here are systems, devices, and methods for measuring a parameter, including but not limited to temperature, voltage, force, pressure, light amplitude, audio amplitude, pH, and an analyte (e.g., lactate, oxygen, and carbon dioxide) level. For example, in some implementations, the systems, devices, and methods described herein may comprise a sensor configured to measure a change in an electrical propagation time (e.g., a delay) or other electrical signal (e.g., resistance, capacitance, current, voltage) corresponding to a parameter. The sensor may be a MEMS sensor comprising a membrane configured to generate a measurable response (e.g., a change in a measurement or electrical signal such as resistance, capacitance, current, voltage) when the membrane interacts with a parameter of interest. For example, the MEMS sensor may comprise a piezoresistive MEMS subassembly and/or an electrochemical MEMS subassembly comprising a piezoresistive membrane and/or electrochemical membrane respectively. In some variations, the MEMS sensor may comprise a strain gauge coupled to the membrane and configured to generate a change in an electrical signal. As used herein, the terms “parameter” and “physical property” are used interchangeably throughout, the terms “sensor” and “sensor assembly” are used interchangeably throughout, and the terms “substrate,” and “wafer” are used interchangeably throughout. The substrate/wafer may be used, for example, to create a die or a chip that may be part of the sensor. The substrate may be a semiconductor substrate, e.g., silicon. Other types of substrates may be employed. Additionally, as often described herein as comprising a piezoresistive MEMS subassembly, it should be appreciated that the sensors (sensor assemblies) may comprise substantially the same features while instead including an electrochemical MEMS subassembly. Put differently, in any of the variations described herein as comprising a piezoresistive membrane, the MEMS subassembly may instead include an electrochemical membrane. Moreover, in some variations, the sensors described herein may be configured to measure multiple parameters and may include 1) one or more piezoresistive membranes (to measure a first parameter type, such as, for example pressure) and 2) one or more electrochemical membranes (to measure a second, different parameter type, such as, for example, an analyte level such as lactate). The sensor may be coupled to or include a compute device (e.g., that includes a microcontroller or processor) configured to receive output from the sensor, determine the measured value of the parameter of interest, and optionally output (e.g., display) the measured value and/or send an indication of the measured value to another compute device.
The sensors may be disposed within a sensor housing to help protect the sensor from fluids (e.g., blood) and/or damage due to other external elements. The sensors may be contained in, positioned within a sensor housing and integrated into an elongate body (e.g., a catheter) used in various devices, for example, blood flow control devices and monitoring devices (e.g., devices that monitor pressure, pH, and/or an analyte such as, for example, lactate, oxygen, carbon dioxide), as further described herein. Though some variations are related to measuring pressure, in other variations, other types of parameters may be measured instead of or in addition to pressure (e.g., temperature, voltage, force, pressure, light amplitude, audio amplitude, pH, lactate, etc.).
The systems, devices, and methods described herein may inherently compensate for variations in temperature, voltage, silicon skew, common mode noise, and the like, and may be useful for medical, automotive, aviation, and industrial applications, especially with size and/or weight constraints. By contrast, conventional PLL multipliers require complex analog modeling of a silicon process and commonly have issues at specific combinations of temperature, voltage, and/or speed of the silicon. However, conventional compensation solutions such as additional circuit elements including a differential amplifier, a differential low-pass filter, offset compensation, and an analog-to-digital converters (ADC) are not needed for the systems, devices, and methods described herein.
Generally, the sensors described herein may comprise a plurality of compensated ring clock multipliers (e.g., oscillator ring circuits) configured to generate and output an accurate higher speed clock signal from a lower speed clock signal. In some variations, an adjustable delay may be calculated for the output clock signal of a first oscillator ring circuit corresponding to a first set of parameters (e.g., temperature, voltage, silicon die). A second oscillator ring circuit may be configured to generate and output a second clock signal that varies in response to the first set of parameters and at least one additional parameter (e.g., pressure). In this variation, the difference between the output clock signals corresponds to a measurement of the sensed parameter (e.g., pressure) that inherently compensates for the first set of parameters (e.g., temperature, voltage, silicon die). In other variations, rather than calculating a delay, the output clock signals from the first and second oscillator ring circuits may be received at a processor (e.g., without calculating delay), and the processor may be configured to calculate the measured parameter based on the output clock signals without calculating delay, as will be described in more detail herein. Additional oscillator ring circuits may be used to measure additional parameters. Moreover, in some variations, the measured parameter may be output as a digital signal which may increase immunity to electrical noise.
In some variations, conventional Wheatstone bridge sensors separate R3 and R4 from the sensor elements R1 and R2. Furthermore, R3 and R4 may be set to be as close in resistance as possible. For example, R1 does not need to equal R3 so long as R3 is equal to R4 such that VBC will depend on the ratio of R1 and R2. However, VBC may comprise an error (e.g., offset) when R3 does not equal R4. This offset may be measured and used to calibrate the sensor (e.g., when the sensor is manufactured or turned on). For example, the sensor may be calibrated by measuring VBC at first and second predetermined pressures. The inherent offset and gain of the sensor circuit may be determined using linear regression such that the sensor may be calibrated.
Similarly, R1 and R2 do not need to have any inherent relationship at any one condition. For example, R1 may be 2000.5 ohms and R2 may be 2002.1 ohms at ambient pressure, and VBC may not be 0 V when R3 equals R4. However, the inherent offset may be removed in the pressure measurement so long as another measurement is made at a different pressure.
However, when used in this configuration in, for example, a blood flow control device, the length of the wires may reduce sensor accuracy. For example, the wires may function as antennas that pick up both common mode noise and differential noise. Conventionally, removal of this common mode noise requires a common-mode low pass filter, and even with the filter may still require a differential amplifier with a high common mode rejection ratio. Furthermore, the wires are generally not matched such that a differential low-pass filter is typically used to filter the differential signal before input to a differential amplifier. Even so, the low-pass filter itself may add very low frequency offsets, phase delays in the signal, and attenuation at higher heartbeat rates that must be compensated in software.
Conventional sensors are subject to different offsets that may reduce measurement accuracy. In some variations, a conventional sensor may comprise an offset compensation circuit comprising one or more of a differential amplifier, potentiometer, and a DAC configured to compensate for the inherent offset introduced by R1 and R2. However, even the offset compensation circuit may add a small gain error to the measurements. Furthermore, silicon-based sensor may be sensitive to temperature changes. For example, a 1° C. change in temperature may correspond to a greater than 1 mmHg change in offset. In some variations, an offset compensation circuit may comprise one or more of a circuit configured to individually measure the individual voltages VB and VC, a resistor, and an ADC configured to measure the current of the entire Wheatstone bridge. The design and implementation of the offset compensation circuit may result in extra cost, size, weight, and manufacturing complexity.
While solid state pressure transduction (SSPT) circuitry like that shown in
Another limitation is due to power supply and ground noise. The Wheatstone bridge arrangement is susceptible to electrical noise on the V-Exc signal that feeds current into R1 and R3 (as shown in
Another limitation is due to electrical noise on the long wires in the catheter. A wire may act as an unintended antenna, and the 50 to 100 cm wires in the catheter may have an undesired amount gain for a wide range of frequencies. The energy captured by wires (aka antenna effect) changes the intended values, and this change is called “noise.” The noise may be dynamic, and may have frequencies from a few Hertz (Hz) to hundreds of millions of Hertz. This type of noise is generally known as Radio Frequency (RF) Noise. Specifically, the 60 Hz alternating current (AC) power currently used in the USA and the 50 Hz AC currently used in Europe may result in particularly high noise levels.
As shown in
As a result of the noise limitations, a set of filters are often used. A first differential filter is often used before VOut is presented to the amplifier. This filters out high frequency common mode noise as well as some of the differential noise. Then another low pass filter is placed after the amplifier. This cuts high frequency noise that would cause the ADC to “alias” the noise to lower frequencies. Finally, a digital low-pass filter is sometimes used in the software to remove any noise that is captured by the ADC.
Some of the electrical noise can be difficult to filter, such as that found in common emergency scenarios-electrosurgery pen usage and cardiac defibrillation. Regulatory agencies have acknowledged this limitation and specifications such as ISO 60601-1 and ISO 60601-2-34 allow for a recovery time after the large noise ceases.
Another limitation of SSPT relates to runtime calibration. At the time SSPT is used, there may be variations in the voltage supplied to the sensors, to the amplifier, and to the ADC chip. These variations may be due to changes in the temperature of those circuits. They may also be due to changes in the output of the various power supplies, especially those that are powered by batteries. The sensors may also have variation with respect to temperature. This often requires additional circuitry and manufacturing costs to compensate for the variations due to temperature.
Another limitation of SSPT relates to interoperability. For a resuscitative endovascular balloon occlusion of the aorta (REBOA) catheter with SSPT sensors above and below the balloon and a display unit outside the body, it can sometimes be desirable to have the catheter itself can be interchangeable so that only one display unit is needed to service multiple catheters. Because the calibration must be performed on the entire analog circuit (sensors in the catheter plus the electronics in the display unit), the interchangeable “boundary” would need to be at the ADC. This may require a separate chassis for the analog circuits and the digital circuits and would add even more cost.
The sensors described here may provide many advantages relative to conventional sensors using, for example, a known Wheatstone Bridge. Examples of these advantages include but are not limited to the following.
First, the sensors (e.g., pressure, force) described herein may utilize a MEMS circuit arrangement in which an analog-to-digital conversion may be performed directly on a sensor die. In some variations, rather than have a very small differential voltage as the output, sensors described herein may produe a digital output (e.g., a serial digital stream), such as a standard universal asynchronous receiver transmitter (UART), that may be easily read directly by a compute device, such as an off-the-shelf microcontroller. Second, use of the sensors described herein may reduce manufacturing costs, system sizes, and system power, and may allow for increased flexibility in how devices utilizing these sensors (e.g., medical devices) are prototyped, designed, and manufactured. Space and power consumption may be important considerations for some pieces of equipment carried into austere settings. The development of fully digital pressure sensors, such as those described herein, greatly simplifies the backend electronics for these devices. For example, at least because the sensors described herein may use, in some variations, power and a precise clock as inputs, the compute device may be greatly simplified compared to known techniques: just a power source, a clock source, and a circuit to receive a serial message (e.g., UART) and convert it to a wired or wireless format. That way, in some variations, the display could be separated by any arbitrary distance. Also, because the sensor is inherently always in “output mode” (rather than read-response mode), the output values may be sent to more than one compute devices.
Third, as will be discussed in more detail herein, the sensors described may provide a digital output (e.g., a serial digital stream indicating pressure), which may allow for disconnection of portions of a device (e.g., in the context of a medical device comprising an elongate body such as a catheter, the catheter shaft) from external electronics, so that the electronics are usable with multiple devices. Moreover, the sensors described herein also allow for replacement of portions of the electronics in the event the electronics are damaged and/or out of power. In variations in which the sensors described herein are utilized in a medical device (e.g., a blood flow regulation device), a portion of the medical device advanced into a patient may remain in the patient while the external electronics (e.g., compute device) are replaced.
Fourth, the sensors described herein may provide higher quality digital outputs than conventional Wheatstone bridge sensors providing analog signals. For example, with respect to use in a pressure sensing application in particular, the digital outputs may have, for example, at least 10,000 times greater noise tolerance than analog signals. As one example, if the digital output is nominally 3.3V for a logic 1 and 0V for a logic 0, a receiver may be capable of tolerating, for example, a noise level of 1V and still distinguish between a 1 or 0. For the analog-based Wheatstone bridge, a noise level of only 100 microvolts might correspond to as much as 4 mmHg of change in the pressure reading. This may be too much error for high fidelity physiologic monitoring that may form the basis of medical devices. In addition, digital messaging schemes increase signal fidelity by also allowing for addition of error detection bits that may further improve confidence that the received message has not been corrupted. Additionally, in some variations, such as those in which a compute device receives a digital value, the temperature of the compute device may have little or no effect and no compensation or calibration may be needed for the circuit generating the digital value. Also, having a digital output from the sensor may eliminate the amplification stage that has previously been used for analog solid state pressure sensors or with fluid-column based pressure sensors. Since there is no analog amplifier, there is also no need to match the voltages between the amplifier and associated ADC.
Fifth, in some variations, the sensors described herein utilize sensor wires that may be immune, or less susceptible to, RF-induced noise. For example, the sensors described herein may utilize sensor wires that are smaller than conventional sensor wires (e.g., <0.1 mm), and thus the sensor wires may be too small to be susceptible to RF-induced noise.
Moreover, having only digital signals traversing the long wires eliminates the need for almost all of the low-pass filters. This may save space on the sensor circuit, reduce complexity, and/or the like.
Sixth, the sensors described herein are easily adaptable across a variety of silicon processes compared to known techniques, thus allowing them to be versatile across processes.
Seventh, the sensors described herein may provide improved fault detection compared to conventional sensing techniques. For example, if any of the sensor wires are damaged, the compute device (e.g., microcontroller) may detect the failure within a short time frame (e.g., 1 sample period), since digital outputs from the sensor will cease.
Eighth, the sensors described herein easily allow for the use of various runtime diagnostics by varying the input clock rate or varying the supplied voltage, which is not possible in many conventional sensing techniques.
While there are many advantages to utilizing the sensors described herein, there may also be challenges in creating a sensor with a built-in analog-to-digital converter (ADC). It may be desirable, for example, for the ADC to add minimal size to the silicon die so that the ADC still fits within the size constraints of the device for the particular application, such as, for example, within an elongate body in a medical device. It may also be desirable, for example, for the sensing element and the ADC be tolerant to voltage variations, since, in some implementations, the sensor die may be at least 50-100 cm away from the power supply. It may also be desirable, for example, for the ADC to be tolerant to variations in sensor location (such as, for example, inside a patient) or temperature.
Some known analog-to-digital conversion is performed using sigma-delta or successive approximation techniques. This may require complex circuits that must be adapted for each silicon process, and may be sensitive to the operating voltage and temperature. Some variations, as will be shown and discussed with respect to
Generally, a sensor system may include one or more of the components to measure and optionally output a parameter using the systems as described herein. A block diagram of an exemplary solid state sensor system 300 is depicted in
Referring back to
The controller 320 may comprise one or more of a processor 322, a memory 324, an input device 326, an output device 328, and a communication device 330, each of which are described in more detail herein. In some variations, the system 300 may be disposed on a single substrate (e.g., single die) or on a plurality of substrates. For example, the sensor 302 may be disposed on a first substrate and the controller 320 may be disposed on a second substrate.
In some variations, the input device 326 may be configured to receive a signal based on a set of output clock signals from the sensor 302. In some variations, the output device 326 may be configured to output data associated with the system 300 as a digital signal. In some variations, the processor 322 and memory 324 may be configured to control the sensor system 300. In some variations, the communication device 330 may be configured to communicate with one or more components of the system 300 and the compute device 340 (e.g., mobile phone, tablet, laptop, desktop PC). In some variations, compute device 340 is a microcontroller.
Note that, although
In some variations, multiple sensors may be coupled to one another. For example, in some variations, a plurality of sensors (two, three, four, or more) may be coupled serially to one another (i.e., daisy chained). In these variations, the clock rate may be modified to account for the daisy chained sensors. As an example, if a 32,768 Hz input clock may have been used for measuring a value from a single sensor, the clock rate in a daisy chained variation may be 32,768 Hz multiplied by the number of sensors in the daisy chain (e.g., use a 65,536 Hz clock if two sensors are daisy chained, use a 98,304 Hz clock if three sensors are daisy chained, etc.). Additionally, an input may be added to the serializer (i.e., shift register) that receives bits from the upstream sensor(s), as shown at
An example of daisy chained sensors is shown in
In some implementations, a sensor (e.g., as illustrated in
In some variations, the sensor may comprise a MEMS subassembly (e.g., a piezoresistive MEMS subassembly, an electrochemical MEMS subassembly) including a membrane and a wall surrounding a measuring portion of the membrane. The wall may be configured to form a cavity between the membrane and a substrate that may provide room for movement (e.g. deflection and/or deformation of the membrane. The membrane (e.g., a measuring portion of the membrane) may be configured to generate a measurable response (e.g., a change in an electrical signal such as resistance, capacitance, current, voltage) when the membrane interacts with a parameter of interest. The substrate may include a first oscillating ring circuit having a first oscillation rate that is modulated by this measurable response from the measuring portion of the membrane and configured to generate a first output count signal, and a second oscillating ring circuit having a second oscillation rate independent from this measurable response and configured to generate a second output count signal. In some variations, the second oscillation rate may be based on a measurement from a reference portion of the membrane, which may be advantageous, but need not be. The sensor may further comprise a processor coupled to at least the substrate that may be configured to determine the parameter based on the first output count signal and the second output count signal. For example, in some variations, the processor may be configured to determine a first parameter value based on the first output count signal and a second parameter value based on the second output count signal. The processor may be further configured to determine a measured parameter based on the first parameter value and the second parameter value. For example, the processor may be configured to adjust the first parameter value based on the second parameter value to provide the measured parameter. The parameter values (first, second, measured) may be any of a variety of parameters of interest, including but not limited to, pressure, pH, or lactate.
In variations in which a reference portion is utilized with the second oscillating ring circuit, the reference portion may be a part of the membrane disposed on the substrate that does not overlie the cavity. Some variations of the sensor may include one or more standoffs extending from the wall, which may be configured to prevent damage to, and/or contamination of, the measuring portion of the membrane. In further variations, the sensor may include a membrane in which at least a part of a top surface of the measuring portion has one or more properties configured to reduce blood clot formation thereon. The one or more properties may be one or more of a surface roughness, hydrophilicity, hydrophobicity, and surface charge of the membrane. In yet another variation, the sensor may include at least one conductor extending from inside the cavity to outside the cavity that may be embedded within the membrane. The at least one conductor may be formed by heavily doping a portion of the membrane. Other portions of the membrane, e.g., some or all of the portion within the cavity (measuring portion), may be lightly doped. Additionally, in some variations, the sensor may include one or more wire guides configured to align one or more wires extending therefrom parallel to a surface of the sensor assembly, receive an end of the one or more wires, and electrically couple the end with the substrate (e.g., circuitry thereon or therein). The one or more wire guides may comprise a slot or channel formed in any portion of the substrate (e.g., top, bottom, side of the substrate). The sensors may also include one or more vias through the substrate connecting the membrane to circuitry on or within the substrate (e.g., CMOS circuitry).
a. Oscillator Circuit
Generally, the oscillator circuits (e.g., compensated ring oscillator) described herein may be configured to receive an input clock signal and generate an output clock signal having a frequency greater than the input clock signal. The oscillator circuit may comprise one or more (e.g., a plurality) of delay circuits (e.g., inverter circuits, such as Schmidt-trigger inverters) arranged in a ring configuration. The oscillator circuit may be configured to generate an output clock signal having a predetermined ratio (e.g., output clock signal is an integer multiple of the input clock signal) by compensating for inherent circuit offsets such as temperature and voltage by adjusting a delay of the oscillator circuit. Circuits suitable for use in the systems, devices, and methods here are described in U.S. Pat. No. 6,911,872, filed Mar. 25, 2003, granted Jun. 28, 2005, and titled “Circuit and Method for Generating a Clock Signal,” which is hereby incorporated by reference in its entirety.
The rate counter circuit 430 may be configured to count the number of output clocks that occur for each single count of the input clock. The delay calculator circuit 440 may be configured to calculate a difference between the output of the rate counter circuit 430 and the predetermined ratio.
A frequency of the output clock signal may be greater than a frequency of the input clock signal. In some variations, the plurality of delay circuits 410 may be coupled to a multiplexer (not shown). In some variations, a first plurality of inverter circuits may be configured in a closed loop with positive feedback. In some variations, the oscillator circuit 400 may be disposed on one or more substrates (e.g., silicon dies).
An exemplary operation the oscillator circuit 400 is described below. For a predetermined ratio of 1000 and a rate counter value of 998 output clock counts for every one input clock counts, the delay calculator circuit 440 may calculate and set an adjustable delay to run slower by 2 counts per input clock using the adjustable delay circuit 420. As another example, an input clock signal having a frequency of 32,768 Hz and a predetermined ratio of 1000 corresponds to an output clock signal having a frequency of 32,768,000 Hz. Accordingly, the total delay of the ring may be about 30.52 ns ( 1/32,768,000). If the propagation time of the individual delay circuit (e.g., inverter circuit) is about 50 picoseconds, then the oscillator circuit may comprise about 61 delay circuits. It should be appreciated that input clock signals having a frequency of 32.768 kHz, for example, may have high precision as they are based on large quartz crystals cut to precise sizes. For example, crystals used in digital watches and computer systems typically achieve accuracies in the range of +/−10 ppm (+/−0.001%) or better. Furthermore, these input clock signals may be transmitted over relatively long distances while retaining immunity to noise. In some variations, the input clock signal may have a frequency of 32,768 Hz, or an integer fraction of that rate (e.g., 16,384 Hz, 8,192 Hz, etc.).
For silicon-based implementations, the oscillator circuit 400 compensates for variations in temperature, voltage, and the inherent speed of a silicon substrate. For example, an increase in temperature corresponds to an increase in propagation time through the delay elements and a slower output clock signal. Conversely, an increase in voltage corresponds to a shorter propagation delay and a faster output clock signal. In some variations, the adjustable delay circuit 420 may comprise a range sufficient to compensate for the variation of propagation delays within an individual silicon process. For example, a substrate (e.g., silicon die) from one manufacturing lot may have propagation delays that vary by up to about 20% from another substrate from another manufacturing lot, even though both substrates were subjected to the same voltage and temperature. The differences in the silicon from manufacturing lot to manufacturing lot are sometimes called the “silicon skew”.
In some variations, the first circuit 510 may comprise a first oscillator circuit (similar to oscillator circuit 400). Similarly, the second circuit 520 may comprise a second oscillator circuit. The first circuit 510 may be configured to receive an input clock signal and output a first output clock signal 514 having a predetermined ratio between the input clock signal and the first output clock signal 514 using an adjustable delay. In some variations, the second circuit 520 may be configured to receive the input clock signal and output a second output clock signal 526 using the adjustable delay. In some variations, the third circuit 530 may be coupled to the first circuit 510 and the second circuit 520, and the third circuit 530 may be configured to generate a third signal 532 based on a difference between the first output clock signal 514 and the second output clock signal 526. The third signal 532 may correspond to a measured parameter. For example, third signal 532 may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude. In some variations, the third signal 532 may be processed to output a parameter signal corresponding to a unit of measurement (e.g., mmHg).
In some variations, the first circuit 510 comprises a first plurality of delay circuits arranged in a ring configuration. The first plurality of delay circuits may comprise a first plurality of inverter circuits and a first adjustable delay circuit 512. The first adjustable delay circuit 512 may comprise a first rate counter. The first plurality of inverter circuits may be coupled to a first multiplexer. The first plurality of inverter circuits may be configured in a closed loop with positive feedback. The first delay circuit may comprise a first resistor-capacitor delay circuit.
The first output clock signal 514 may vary based on a first set of parameters and the second output clock signal 526 may vary based on a second set of parameters different from the first set of parameters. For example, the first set of parameters may comprise one or more of temperature and voltage. In some variations, the second set of parameters may comprise temperature, voltage, and one or more of force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction. That is, the second set of parameters may include the first set of parameters and at least one additional parameter.
In some variations, the third signal 532 may be processed to calculate a difference in the second output clock signal 516 relative a starting condition (e.g., tare). For example, a tare signal may be provided as a separate input or as a signal using an in-band encoding on the input clock signal.
In some variations, the second circuit 520 comprises a second plurality of delay circuits arranged in a ring configuration. The second plurality of delay circuits may comprise a second plurality of inverter circuits and a second adjustable delay circuit 522. The second adjustable delay circuit 522 may comprise a second rate counter. The second plurality of inverter circuits may be coupled to a second multiplexer. The second plurality of inverter circuits may be configured in a closed loop with positive feedback. The second adjustable delay circuit 522 may comprise one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit. The second circuit 520 may comprise at least one delay circuit configured to vary based on at least one additional parameter different than the first circuit 510.
In some variations, the second plurality of delay circuits may comprise the same delay circuits as the first set of delay circuits and at least one additional delay circuit configured to vary based on a parameter to be measured (e.g., pressure). In this manner, the output clock signals 514, 526 from the respective first circuit 510 and second circuit 520 may differ as the parameter to be measured (e.g., pressure) changes. In variations where the first circuit 510 and the second circuit 520 are disposed on the same substrate (e.g., same silicon die), an adjustable delay due to temperature and voltage offsets will be the same for the first circuit 510 and the second circuit 520. Thus, a difference between first output clock signal 514 and the second output clock signal 526 will be due to changes in the measured parameter (e.g., pressure) and independent of offsets such as temperature, voltage, and silicon skew. In some variations, the additional delay circuit of the second circuit 520 may comprise one or more of a resistor-capacitor delay circuit, a resistor-inductor delay circuit, and a capacitive delay circuit. Any physical property (e.g., pressure, force, light amplitude, audio amplitude, voltage) that may result in a change in electrical propagation time (e.g., delay) may be measured in this manner. For example, the sensor 500 may be used for electrochemical analysis where a chemical reaction results in a change in the resistance or capacitance. The systems, devices, and methods described reduce circuit complexity and size by avoiding precision current sources and voltage measurement ADCs.
In some variations, the sensor 500 may be disposed on one or more substrates (e.g., silicon dies). For example, a single substrate may comprise the first circuit, the second circuit, and the third circuit. In other variations, a first substrate may comprise one of the first circuit and the second circuit, and a second substrate may comprise the other of the first circuit and the second circuit. Furthermore, each circuit of the sensor 500 may be disposed on its own substrate or any combination of substrates.
An exemplary operation the oscillator circuit 500 is described below. For an input clock signal having a frequency of 32,768 Hz and a first output clock signal having a frequency of 32,768,000 Hz, a predetermined sample rate of 200 Hz (e.g., 5 millisecond sample period), a span of 1000 mmHg pressure (min to max), a predetermined resolution of 0.25 mmHg, 4,000 quantized levels are required (1,000 mmHg/0.25 mmHG=4,000 quantized levels). In this case, the second circuit 520 may have about 163,840 clocks per 5 ms sampling period. One clock period is 1/32,768,000 second (30.52 ns). Therefore, the delay varies by 30.52 ns for each 0.25 mmHg of pressure. It should be appreciated that the 4,000 quantized levels is much less than the 163,840 clocks each 5 millisecond period such that the count may be measured using a digital counter. If a sensor measurement requires more than 30.52 ns for each 0.25 mmHg of pressure, then a faster clock rate may be used. Conversely, if the variation in delay is more than 30.52 ns for each 0.25 mmHg of pressure, then a slower clock may be used. In other variations, other rates may be used, such as a different clock frequency (e.g., 16,384 Hz, 65,536 Hz, etc.) and/or different sampling rate (e.g., 256 Hz).
In some variations, an optional fourth circuit (e.g., fourth circuit 310 in
In some variations, a fourth circuit may be coupled to the third circuit. The fourth circuit may be configured to receive the input clock signal and output a fourth output clock signal using the adjustable delay. The third circuit may be configured to generate a fifth signal based on a difference between the first output clock signal and the fourth output clock signal. The fifth signal corresponds to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude. In this manner, the sensor 500 may be configured to measure a plurality of parameters while compensating for offsets without offset compensation circuits.
In some variations, the sensor 500 may be powered by a set of two wires: a first wire associated with a positive voltage and a second wire associated with a ground. In some variations, the positive voltage wire may be omitted and power may be derived only from the input clock signal. In some variations, the peak voltage of the input clock signal may be higher than the peak voltage of the serial output signal.
In some variations, the sensors described herein may be disposed on a 50 nm process including about 5,000 gates and about 10,000 gates/mm2. In some variations, a die may comprise a size of more than about 0.3 mm2. In some variations, the sensor 500 may comprise a low-pass filter to reduce noise on the power supplied to the delay elements (e.g., noise above 16.384 kHz corresponding to a Nyquist rate of a 32.768 kHz crystal).
Referring to
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Although
In some variations, a temperature of the first or second ring oscillator may be determined using pulse time delay measurements. For example, time for a pulse or a known voltage may be measured, and if the voltage is tightly controlled, an assumption may be made that the time will be different for other pulses based only on temperature.
The various circuits discussed herein may be included on any number of chips, die, and/or substrates. In some variations, the various circuits discussed herein may be included across a plurality of chips, die, and/or substrates.
The sensor delay may vary according to an attribute that is to be measured. In an example configuration where the sensor delay varies according to pressure, pressure could also affect the speed of the oscillation of Ring #1 by inclusion of a piezoresistive pressure sensitive unit within the die. Thereby, changes in pressure result directly in changes in the oscillation rate of just Ring #1. Note that oscillating Ring #2 is configured to have no change with respect to the change in pressure (since there is no sensor delay component).
A precise low-speed input clock, such as 32.768 kHz, may be divided to create a sampling rate, such as 200 Hz (e.g., as shown in
Ring #2 in
In variations in which the sensors described herein are utilized to measure pressure in a clinical setting, a system or medical device with a pressure sensor may be “tared” (zeroed) prior to insertion into the body. The system or device may then be configured to determine and/or store the clock rate for both rings. When the sensor is placed within the body, the temperature may go up, and Ring #2 may run slower. The amount Ring #2 runs slower may be factored into the calculations for converting the Ring #1 rate to pressure. In some variations, however, other physical properties like pH or lactate may be measured in addition to or instead of pressure.
While any clock may be used for the low-speed input clock, in some variations, a 32.768 kHz clock maybe desirable. For example, in variations in which preciseness is particularly desirable because, the sensors described herein may utilize clocks that are derived from crystals. These crystals routinely achieve accuracies of +/−5 ppm (0.0005%), thus use of these crystals would add only a small error (which is likely to be essentially inconsequential (estimated to be in the range of 0.5 mmHg for a pressure sensor)).
Once the two counter values are latched, a small area on the die may be used to send those values out as a digital output (e.g., digital communications packet). In some variations, the values may be transmitted as a serial packet that maybe read directly by a compute device (e.g., microcontroller 1130A or 1130B). In some variations, the Universal Asynchronous Receiver Transmitter (UART) protocol h may be utilized. The UART protocol supports communications packets that may be as short as 1 byte and as many as thousands of bytes. As an example, in a variation in which each counter is 19 bits, only 38 bits need to be sent, which may fit within a simple 5 byte (40 bit) packet. While UART is discussed herein and may in some variations be utilized, in other variations, other communication protocols may be used instead of or in addition to UART.
At least some variations described herein may use two or more rings, and the use of a compute device to perform the run-time calibration.
While the above example involves pressure measurement, the same general technique may measure other physical properties such as force, light amplitude, acoustics, or electrochemical reactions. The sensor delay may result in a measurable change in an impedance, capacitance, or inductance; otherwise, the sensor delay could result in a change in the propagation speed of the electrical signals within the ring.
One benefit of this sensor arrangement is that the die is not limited to 2 rings. For example, in some variations, the sensors described herein may comprise a 3rd ring with an oscillation rate that may be modified by a different physical property. For example, the 3rd ring may be set up to have additional sensitivity to temperature (vs. Ring #2) and thus may provide a highly accurate report of a patient's core temperature. A 4th ring may be employed with an oscillation rate that may vary based on electrochemical properties, such as pH. At higher sample rates, it may be possible to pick up acoustic signatures associated with heart valve opening/closing. In each of these variations, the analog signals may be converted to digital data that may be sent via a single wire using digital messages. Additional sensing may simply require a slightly larger message. For example, at a 256 Hz sample rate and a 32.768 kHz input clock, a single output wire may send out 128 bits during each sample period. This could accommodate 5 different sensors, each with 19 bit resolution. If more resolution or a higher sample rate is desired, the clock rate may be doubled or one or more additional wires may be added. The ability to transition from analog to digital signaling has tremendous implications for signal fidelity, interoperability with existing patient monitoring devices, and miniaturization of SSPT devices, and may be applied across many aspects of patient care, especially in prolonged field care (PFC) where size and power requirements are paramount.
As can be seen,
In some variations, start and stop bits may be latched directly into the shift register. For example,
In one example, the serial output may be at a rate that is half the input clock. In one example, a single flip flop may be used to create a 16,384 kHz clock, and a 6 flip flop divider of that 16,384 kHz clock is used to get a 256 Hz sample rate. At each sample boundary, the values from the two counters may be latched. In some variations, rather than build state machines to handle the start/stop bits, the 38 counter bits (2×19) and the start/stop bits may be latched directly into a single 47 bit shift register. In one example, the shift register only needs to be 47 bits (and not 50 bits) because there are 10 bits per byte, but the last 3 bits of byte 5 are always 1. At the output clock rate (16,384 kHz), a bit from the shift register is shifted out and a “1” is shifted in at the other end. This will enforce the “1” as the output during the time between the 5 bytes.
In some variations, the sensors described here may be used to determine a measured parameter without use of a delay (e.g., without use of a delay as described in the context of
As an example, in some variations, a MEMS subassembly that changes resistance at one oscillating ring circuit but not the other to measure a physical property (e.g., pressure, lactate, pH) may be used. Put differently, in some variations, the electrical signal provided by the MEMS subassembly may be a resistance. Alternatively or additionally, a property other than resistance may be changed at one oscillating ring circuit and not the other oscillating ring circuit, such as capacitance, voltage, current, and/or the like. For example, in some variations, an electrochemical membrane may be utilized that provides an electrical signal associated with a chemical reaction tied to the parameter of interest occurring at or via the membrane. In these variations, the electrical signal related to the chemical reaction may be used at one oscillating ring circuit and not the other oscillating ring circuit, thus allowing, in a similar manner as discussed above, the sensor to be used to determine a measured parameter of interest. In some implementations, each sample period measuring the amount of latches is counted.
b. Output Device
Generally, an output device as described herein may be configured to output a signal corresponding to a measured parameter as described herein. For example, the output signal may be a digital signal such that circuits such as an ADC are not needed, thus reducing device complexity. In some variations, a controller may comprise an output device configured to output the third signal as a digital signal. For example, the output device may be configured to output the third signal as a set of binary encoded bits at a periodic rate. In some variations, the output device may comprise one or more of a wire configured for wired transmission and an antenna configured for wireless transmission. In some variations, the third signal may be encoded and/or output on a separate wire to increase noise immunity.
As described herein, a measured parameter may be represented by 4,096 quantized levels that may be transmitted as a digital signal using 12 bits at a predetermined rate (e.g., once per 5 milliseconds, 3,200 bits per second). It should be appreciated that transmission speeds below 5,000 bits per second have high noise reliability because each bit is long enough that the noise bursts are shorter than the individual bit time.
In some variations, the digital signal comprises one or more of standard binary encoding (e.g., UART), Pulse Width Modulation (PWM), Manchester encoding, and the like. In some variations, the output device may comprise a universal asynchronous receiver-transmitter (UART). Accordingly, the output device may be absent a programmable gain amplifier (PGA) and/or ADC, thus reducing component count and manufacturing complexity. In some variations, the digital signal may be output using one or more of a wire and antenna. There are several methods for providing the binary encoded value on a single wire including a standard NRZ or NRZI UART technique, with a start bit, 8 encoded bits, and a stop bit. In some variations, the digital signal may be output as multiple bytes of ASCII text and/or greyscale encoding.
In some variations, the output device may include a serializer (e.g., serializer circuit 1120), where the serializer may include circuitry configured to convert parallel data to serial data and/or vice versa. In some variations, the output device may include an output register, where the output register may include circuitry that includes flip flops and is configured to store data.
c. Processor
A sensor system 300, as depicted in
The processor 322 may incorporate data received from the memory 324 and compute device(s) 340 to control the system 300. The memory 324 may further store instructions to cause the processor 322 to execute modules, processes, and/or functions associated with the system 300 and/or compute device(s) 340. The processor 322 may be any suitable processing device configured to run and/or execute a set of instructions or code and may comprise one or more microcontrollers, data processors, image processors, graphics processing units, physics processing units, digital signal processors, and/or central processing units. The processor 322 may be, for example, a general purpose processor, a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), configured to execute application processes and/or other modules, processes, and/or functions associated with the system and/or a network associated therewith. For example, the processor 322 may be a dual core microcontroller. The underlying device technologies may be provided in a variety of component types such as metal-oxide semiconductor field-effect transistor (MOSFET) technologies like complementary metal-oxide semiconductor (CMOS), bipolar technologies, polymer technologies (e.g., silicon-conjugated polymer and metal-conjugated polymer-metal structures), mixed analog and digital, combinations thereof, and the like.
d. Memory
Some variations of memory 324 described herein relate to a computer storage product with a non-transitory computer-readable medium (also may be referred to as a non-transitory processor-readable medium) having instructions or computer code thereon for performing various computer-implemented operations. The computer-readable medium (or processor-readable medium) is non-transitory in the sense that it does not include transitory propagating signals per se (e.g., a propagating electromagnetic wave carrying information on a transmission medium such as air or a cable). The media and computer code (also may be referred to as code or algorithm) may be those designed and constructed for a specific purpose or purposes. Examples of non-transitory computer-readable media include, but are not limited to, flash memory, non-volatile memory (e.g., Intel® Optane™, 3D XPoint™), magnetic storage media such as hard disks, floppy disks, and magnetic tape; optical storage media such as Compact Disc/Digital Video Discs (CD/DVDs), Compact Disc-Read Only Memories (CD-ROMs), and holographic devices; magneto-optical storage media such as optical discs; solid state storage devices such as a solid state drive (SSD) and a solid state hybrid drive (SSHD); carrier wave signal processing modules; and hardware devices that are specially configured to store and execute program code such as Application-Specific Integrated Circuits (ASICs), Programmable Logic Devices (PLDs), Read-Only Memory (ROM), and Random-Access Memory (RAM) devices. Other variations described herein relate to a computer program product, which may include, for example, the instructions and/or computer code disclosed herein.
The systems, devices, and/or methods described herein may be performed by software (executed on hardware), hardware, or a combination thereof. Software modules (executed on hardware) may be expressed in a variety of software languages (e.g., computer code), including C, C++, Java®, Python, Ruby, Visual Basic®, and/or other object-oriented, procedural, or other programming language and development tools. Examples of computer code include, but are not limited to, micro-code or micro-instructions, machine instructions, such as produced by a compiler, code used to produce a web service, and files containing higher-level instructions that are executed by a computer using an interpreter. Additional examples of computer code include, but are not limited to, control signals, encrypted code, and compressed code.
e. Communication Device
In some variations, sensor systems 300 described herein may communicate with one or more of a blood control device, networks, and computer systems through a communication device 330. In some variations, the sensor systems 300 may be in communication with other devices (e.g., compute devices) via one or more wired and/or wireless networks. A wireless network may refer to any type of digital network that is not connected by cables of any kind. Examples of wireless communication in a wireless network include, but are not limited to Bluetooth, cellular, radio, satellite, and microwave communication. However, a wireless network may connect to a wired network in order to interface with the Internet, other carrier voice and data networks, business networks, and personal networks. A wired network is typically carried over copper twisted pair, coaxial cable and/or fiber optic cables. There are many different types of wired networks including wide area networks (WAN), metropolitan area networks (MAN), local area networks (LAN), Internet area networks (IAN), campus area networks (CAN), global area networks (GAN), like the Internet, and virtual private networks (VPN). Hereinafter, network refers to any combination of wireless, wired, public and private data networks that are typically interconnected through the Internet, to provide a unified networking and information access system. In some variations, any of the data stored in memory 324 may be transmitted using the communication device 330.
Cellular communication may encompass technologies such as GSM, PCS, CDMA or GPRS, W-CDMA, EDGE or CDMA2000, LTE, WiMAX, and 5G networking standards. Some wireless network deployments combine networks from multiple cellular networks or use a mix of cellular, Wi-Fi, and satellite communication. In some variations, the network interface may comprise a radiofrequency receiver, transmitter, and/or optical (e.g., infrared) receiver and transmitter. The communication device 330 may communicate by wires and/or wirelessly with one or more components of the systems 300.
The sensors described herein may be contained in and/or positioned within a sensor housing and integrated into an elongate body (e.g., a catheter) used in various devices, such as, for example, blood flow control devices and pressure monitoring devices, as further described below. The sensors may monitor physiologic conditions during a medical procedure and/or monitor patient physiology during routine and critical medical care. In some variations, the sensor housing may be a tubular member including an opening (e.g., a window) configured to expose the sensor to the surrounding environment (e.g., blood within a blood vessel). One or more sensor housings may be integrated into the elongate body, depending on the number of sensors included in the elongate body. In another variation, the sensor and/or the sensor housing may be configured to be small in size (e.g., have a small diameter) so that the sensor may be integrated into an elongate body (e.g., a catheter) for advancement into a blood vessel or advanced through an arterial or venous catheter (e.g., an arterial or venous access line). The sensor housing may be configured to protect the sensor(s) from damage due to moisture or fluid intrusion (e.g., upon exposure to blood) and/or protect the sensor(s) from the effects of pressurization (e.g., pressure from a balloon of a blood flow control device).
The sensor housing may be formed of any suitable biocompatible material. For example, in some variations, the sensor housing may be formed from a polymer, such as, for example, Polytetrafluoroethylene (PTFE), polyimide, Pebax®, thermoplastic polymers, a combination thereof, and the like. Exemplary thermoplastic polymers may be a polycarbonate, a polycarbonate/acrylonitrile-butadiene-styrene terpolymer blend, etc. In some variations, the sensor housing may be formed from a metal, e.g., stainless steel, a bondable metal alloy, or a combination thereof. In one variation, the sensor housing comprises stainless steel.
The sensor housing may have any suitable size, shape, and geometry. For example, the sensor housing may have a tubular, a rectangular, a square, or an ovular shape. In one variation, the sensor housing may be tubular in shape and include an opening (e.g., a window) as mentioned above. The dimensions of the sensor housing may be such that the sensor tightly fits in the sensor housing, thereby minimizing the utilization of space on the elongate body. As mentioned above, in some variations, the sensor housing may comprise a tubular shape. In these variations, the inner diameter of the sensor housing may be about 0.01 inches to about 0.04 inches, including all values and sub-ranges therein. In some variations, the inner diameter of the sensor housing may be for example about 0.012 inches (0.30 mm) to about 0.035 inches (0.89 mm), about 0.015 inches (0.38 mm) to about 0.03 inches (0.76 mm), about 0.017 inches (0.43 mm) to about 0.025 inches (0.64 mm), or about 0.019 inches (0.48 mm) to about 0.022 inches (0.56 mm), including all values and sub-ranges therein. In one variation, the inner diameter of the sensor housing may be about 0.02 inches (0.51 mm). In some variations, the outer diameter of the sensor housing may be about 0.02 inches (0.51 mm) to about 0.08 inches (2.0 mm), including all values and sub-ranges therein. In some variations, the outer diameter of the sensor housing may be for example about 0.021 inches (0.53 mm) to about 0.06 inches (1.5 mm), about 0.022 inches (0.56 mm) to about 0.04 inches (1.0 mm), about 0.023 inches (0.58 mm) to about 0.03 inches (0.76 mm), about 0.024 inches (0.61 mm) to about 0.027 inches (0.69 mm), including all values and sub-ranges therein. In one variation, the outer diameter of the sensor housing may be about 0.025 inches (0.64 mm).
The sensor contained within the tubular sensor housing (e.g., the housing of
Also described here are methods for measuring a physical property using the devices and systems described herein. In particular, the systems, devices, and methods described herein may be used to accurately measure a parameter in a fewer number of steps and in a compact circuit configuration form factor. In some variations, a first output count signal may be generated using a first oscillating ring circuit. The first oscillating ring circuit may have a first oscillation rate modulated by an electrical parameter of a membrane of a MEMS subassembly of a sensor. A first value for the physical property may be determined based on the first output count signal. Further, a second output count signal may be generated using a second oscillating ring circuit having a second oscillation rate that may be independent of the physical property. A correction value may be determined based on the second output count signal and a measured value for the physical property may be determined based on the first value and the correction value. For example, the first value may be adjusted based on the correction value to generate the measured value. In these variations, the aforementioned measured value may be determined without using an adjustable delay.
In step 604, a first output clock signal may be generated having a predetermined ratio between the input clock signal and the first output clock signal using an adjustable delay. In some variations, a frequency of the first output clock signal may be greater than a frequency of the input clock signal.
In step 606, a second output clock signal may be generated using the adjustable delay. In some variations, a frequency of the second output clock signal may be greater than a frequency of the input clock signal.
In some variations, the first output clock signal may vary based on a first set of parameters and the second output clock signal may vary based on a second set of parameters different from the first set of parameters. For example, the second set of parameters may include first set of parameters and at least one additional parameter (e.g., the parameter of interest to be measured). In some variations, the first set of parameters may comprise one or more of temperature and voltage. For example, the second set of parameters may comprise temperature, voltage, and one or more of force, pressure, light amplitude, audio amplitude, and resistance or capacitance corresponding to a chemical or physical reaction.
In step 608, a third signal may be generated based on a difference between the first output clock signal and the second output clock signal. In some variations, the third signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.
Optionally, in step 610, the third signal may be output as a digital signal. For example, the third signal may be output as a set of binary encoded bits at a periodic rate. In other variations, the output may be encoded using non-binary schemes, such as trinary or pulse-width modulation.
Optionally, in step 612, the method may comprise generating a fourth output clock signal using the adjustable delay and optionally, in step 614, may further comprise generating a fifth signal based on a difference between the first output clock signal and the fourth output clock signal. In some variations, the fifth signal may correspond to one or more of temperature, voltage, force, pressure, light amplitude, and audio amplitude.
Optionally, in step 618, the method may further comprise outputting the fifth signal as a digital signal. For example, the fifth signal may be output as a set of binary encoded bits at a periodic rate.
Another method is related to daisy chaining, as discussed at, for example,
Some methods for measuring a parameter may utilize sensors including a MEMS component, e.g., a piezoresistive MEMS subassembly, an electrochemical MEMS subassembly. The methods may employ any sensor described herein and may generally include generating a first output count signal using a first oscillating ring circuit having a first oscillation rate at a measuring portion of a membrane of a piezoresistive MEMS subassembly, and generating a second output count signal using a second oscillating ring circuit having a second oscillation rate. The methods may further include determining a delay value based on the difference between the first output count signal and the second output count signal. Additionally or alternatively, a parameter may be determined based on the first output count signal and second output count signal without determining a delay value; instead, for example, a processor may calculate an initial parameter based on the first output count signal then adjust the initial parameter based on the second output count signal. In some variations, the membrane may further include a reference portion, and the second oscillating rate may be measured based on a measurement from the reference portion. Additionally or alternatively, the second oscillating rate may be entirely independent of the membrane (e.g., not be measured using the reference portion).
In some instances, it may be useful for the sensors described herein to include a current-starved ring oscillator instead of a traditional ring oscillator.
In general, the oscillators described herein may be designed to reduce the effects of parasitic capacitance on ring performance and/or include design elements that improve noise immunity (e.g., include a LDO to improve noise immunity). Some aspects of MEMS fabrication may also be beneficial. For example, the MEMS may have a substantially flat surface without etching a trough in silicon. As such, space below the MEMS structure remains usable, which may be 65% of the die area in some instances. The fabrication flow may also support wire bonding from the top and friction bond on the bottom.
In some variations, the sensors described herein may be dimensioned (e.g., have a length, width, thickness, and/or shape) for use with medical devices (e.g., a catheter of a blood flow control device or other monitoring device) or other devices and systems with significant space constraints such that a smaller and/or thinner sensor may be needed and/or desirable For example, the sensors may be very thin (e.g., less than about 140 microns) so that they may be incorporated into the catheter wall, as further described below. In one variation, the sensor (e.g., sensor assembly) may include a piezoresistive MEMS subassembly. In this variation, the piezoresistive MEMS subassembly may be coupled to a substrate. The piezoresistive MEMS subassembly may include a membrane and a wall surrounding a measuring portion of the membrane, which may be configured to form a cavity between the membrane and the substrate to allow deflection of the membrane. In some variations, the measuring portion of the membrane may be configured to deflect in response to an externally applied pressure, e.g., blood pressure. The piezoresistive MEMS subassembly may also include a reference portion, which may, in some variations, be a reference portion of the membrane. The reference portion of the membrane may be coupled to the substrate. For example, referring to
When the sensor includes a piezoresistive MEMS subassembly, the subassembly may be coupled to a substrate by various bonding techniques, including use of a passivation layer, and with or without annealing at an elevated temperature. The substrate may be a semiconductor substrate, e.g., silicon, and may comprise any suitable material. The substrate may also have any suitable shape (e.g., rectangular, square, circular, ovular, or triangular), and may have a thickness (height) between about 90 microns and about 100 microns, including all values and sub-ranges therein. For example, the substrate may have a thickness of about 90 microns, about 91 microns, about 92 microns, about 93 microns, about 94 microns, about 95 microns, about 96 microns, about 97 microns, about 98 microns, about 99 microns, or about 100 microns. In some variations, the substrate may have a thickness of about 90 microns.
The substrate may include one or more circuits. In one variation, the substrate may include CMOS (complementary metal-oxide semiconductor) circuitry such as one or more of an oscillating ring (e.g., two oscillating rings), a latch, a counter, and a serializer. In some variations, the substrate may include a first oscillating ring circuit having a first oscillation rate modulated by an electrical parameter of the measuring portion of the membrane configured to generate a first output count signal, and a second oscillating ring circuit having a second oscillation rate, which may or may not include a measurement from a reference, e.g., a reference portion of the membrane, configured to generate a second output count signal. In some variations, a processor coupled to at least the substrate may be configured to determine a delay value based on the difference between the first output count signal and the second output count signal. The processor may be further configured to use the delay value to determine a parameter, e.g., pressure. In other variations, a first value for the parameter may be determined based on the first output count signal, and a correction value may be determined based on the second output count signal; thereafter, the first value may be adjusted based on the second output count signal. The parameter may be used to adjust expansion of an expandable member, such as a balloon of a blood flow control device, or otherwise inform treatment decisions for a patient, e.g., when the parameter measures pH or a concentration or amount of an analyte such as lactate, oxygen, carbon dioxide.
The sensors described herein may further include one or more wire guides within the substrate configured to align one or more wires extending therefrom parallel to a surface of the sensor assembly. The one or more wire guides may be configured to receive an end of the one or more wires, and electrically couple the end to circuitry within the substrate. In addition to helping with wire alignment, the one or more wire guides may help to minimize the thickness of the sensor overall by providing low profile wire integration. The wires may have a gauge ranging from 46 to 44 (diameter ranging from about 40 microns to about 51 microns, respectively). In one variation, e.g., when the sensor is employed to measure blood pressure, the wire may be a 46 gauge wire. The wires may have a copper core and gold clad.
The one or more wire guides may include a slot or channel formed in any part (e.g., top, bottom, and/or side) of the substrate. For example, one or more wire guides may be disposed on a first side of the substrate, and one or more vias may be disposed on a second side of the substrate opposite the first side. In one variation, as shown in
The MEMS subassembly (e.g., piezoresistive, electrochemical) may include a membrane. The membrane may extend across the entirety of the substrate or a portion thereof. A wall formed on the membrane may surround a measuring portion of the membrane. A cavity may be disposed beneath the measuring portion of the membrane, between the measuring portion and the substrate. In some variations, the subassembly may include a membrane stop that limits deflection of the membrane within the cavity. In other variations, the subassembly may include one or more standoffs, e.g., on the membrane, extending away from the cavity. The one or more standoffs may be configured to prevent damage and/or contamination of the measuring portion of the membrane. In yet further variations, the membrane may include one or more properties, coatings, or layers configured to reduce blood clot formation thereon.
The membrane may be configured to generate a measurable response (e.g., a change in an electrical signal such as resistance, capacitance, current, voltage) when the membrane interacts with a parameter of interest. The membrane may be a MEMS substrate (e.g., a MEMS wafer), which may comprise silicon (e.g., single crystal silicon). The membrane may have a thickness between about 1.0 micron to about 10 microns, including all values and sub-ranges therein. For example, the membrane may have a thickness of about 1.0 micron, about 2.0 microns, about 3.0 microns, about 4.0 microns, about 5.0 microns, about 6.0 microns, about 7.0 microns, about 8.0 microns, about 9.0 microns, or about 10 microns. In some instances, it may be useful for the membrane to have a thickness of about 1.0 micron.
A wall may be formed on the MEMS substrate. In the assembled state of the sensor, e.g., after the MEMS substrate is flipped onto a CMOS substrate, as further described below, the wall may be disposed beneath the membrane such that the top surface of the wall contacts the bottom surface of the membrane and forms a gap between the membrane and the CMOS substrate. The gap may form a sealed cavity having an initial pressure set therein. The wall may be configured to surround a measuring portion of the membrane. For example, the wall may form a continuous border surrounding the measuring portion of the membrane. The border may have any suitable shape, e.g., rectangular, square, round, ovular, triangular. In one variation, the border may be rectangularly shaped. The height of the wall may be any suitable height that allows deflection of the membrane, and may be between about 5.0 microns and about 10 microns, including all values and sub-ranges therein. For example, the height of the wall may be about 5.0 microns, about 6.0 microns, about 7.0 microns, about 8.0 microns, about 9.0 microns, or about 10 microns.
When the sensors are used in the vasculature, at least a part of a top surface of the measuring portion may include one or more properties and/or surface structures configured to reduce blood clot (i.e., thrombus) formation thereon. The one or more properties may be one or more of a surface roughness, hydrophilicity, hydrophobicity, and surface charge of the membrane. For example, as shown in
In some variations, the membrane may include one or more embedded conductors to help maintain a robust cavity seal (i.e., a tight seal) between the wall and the substrate when the conductors extend beyond the wall. The one or more conductors may be embedded within the membrane, such as, for example, by doping the membrane. For example, referring to
The piezoresistive MEMS subassembly may include a cavity 2820 between the measuring portion 2822 of the membrane and the substrate 2824 formed by the wall 2826 of the subassembly, as shown in
As previously mentioned, the cavity may be configured to allow deflection of the membrane. However, in some instances, it may be useful for the subassembly to include a membrane stop to prevent over deflection of the membrane. As shown in
The sensors described herein may also include one or more standoffs extending from the membrane (e.g., away from the cavity) configured to prevent damage to, or contamination of, the measuring portion of the membrane. The height of the one or more standoffs may be between about 20 microns to about 50 microns, including all values and sub-ranges therein. For example, the height of the one or more standoffs may be about 20 microns, about 25 microns, about 30 microns, about 35 microns, about 40 microns, about 45 microns, or about 50 microns. The one or more standoffs may have any suitable cross-sectional shape, e.g., circular, square, rectangular, triangular, ovular, etc. In one variation, the one or more standoffs may have a cylindrical in shape. The cylinders may have a height between about 20 microns to about 50 microns, as mentioned above, and a diameter between about 20 microns to about 50 microns, including all values and sub-ranges therein. For example, the cylinder diameter may be about 20 microns, about 25 microns, about 30 microns, about 35 microns, about 40 microns, about 45 microns, or about 50 microns.
The one or more standoffs may be configured on the membrane in any suitable manner. For example, when a plurality of standoffs is employed, they may be disposed about the periphery of the membrane, e.g., along one or more edges of the membrane. In some variations, the plurality of standoffs may be symmetrically or asymmetrically spaced about the membrane periphery. When the wall is configured as a rectangularly shaped border 2802 on the membrane, as shown in
Methods of manufacturing piezoresistive MEMS sensors are also described herein. In general, and as illustrated in
The systems and devices described herein are not particularly limited and may be used in a variety of industries and applications. For example, the systems and devices may be used with or otherwise incorporated into medical devices, such as systems and devices for monitoring physiologic states in patients and/or physiologic conditions during medical procedures. In some variations, these systems may include devices comprising an elongate body (e.g., a catheter) with one or more sensors described herein for monitoring physiologic conditions during a medical procedure and/or or monitoring patient physiology over prolonged periods of time during routine and critical medical care. In some instances, these systems may include blood flow control devices. In some variations, the devices may be used to measure pH and/or an analyte, e.g., a lactate level, an oxygen level, or a carbon dioxide level. For example, the devices may be configured to perform arterial monitoring and include one or more the sensors described herein on an arterial catheter (to measure, e.g., pH, a lactate level, an oxygen level, or a carbon dioxide level). In other variations, the devices may be used to measure (or monitor) blood pressure. In these variations, the devices may be configured to measure blood pressure at any location within the body. For example, the devices may be placed in the central arterial vasculature (e.g., aorta, pulmonary artery) or central venous vasculature (e.g., vena cava), or the peripheral arterial vasculature (e.g., femoral artery, radial artery) or peripheral venous vasculature (e.g. femoral vein, radial vein) and used to measure blood pressure therein. In one variation, the devices may measure blood pressure in the aorta. In other variations, the devices may measure blood pressure in the radial artery. The pressure measurements may or may not be made using devices that include an expandable member, e.g., an expandable balloon.
The expandable member 810 may be one of disposed on, coupled to, integrated with, attached to, and/or affixed to the shaft of the elongate body 802 and a size of the expandable member 810 may be controllable by a controller or a user. For example, the expandable member 810 may be configured to expand and contract and/or inflate and deflate such that the size (e.g., volume) of the expandable member 810 may change during use of the blood flow control device. During use, blood flow may be regulated or otherwise controlled by changing a size of the expandable member 810, thereby altering the area of the blood vessel that is occluded by the expandable member 810. Fluid and/or compressed gas may be delivered through one or more lumens in the elongate body 802 in order to control and/or adjust the size (e.g., volume) of the expandable member 810. Thus, in some variations, the expandable member 810 may be strategically placed within the aorta of a patient and the size of the expandable member 810 may control blood flow through the aorta of the patient such that blood flow distal to expandable member 810 may be impeded to augment blood pressure proximal to expandable member 810. The outer surface of the expandable member 810 may be configured to contact or otherwise interface with the wall(s) of the patient's blood vessel (e.g., at complete occlusion). The expandable member 810 may comprise any suitable elastomeric material (e.g., polyurethane, silicone, etc.). Alternatively, the expandable member may comprise polyester, nylon, etc. In some variations, the expandable member 810 may comprise a shape memory material.
The blood flow control device may comprise sensors of any variation described herein. For example, in some variations, the blood flow control device may include one or more (e.g., two, three, four or more) sensors of any variation described herein configured to measure pH or an analyte level (e.g., a lactate level, an oxygen level, a carbon dioxide level, etc.). In other variations, the blood flow control device may comprise one or more (e.g., two, three, four or more) pressure sensors of any variation described herein integrated into the elongate body 802. A distal sensor, the position of which is indicated by reference numeral 811b, may be disposed between a tip of the elongate body 802 and the expandable member 810. A proximal sensor, the position of which is indicated by reference numeral 811a, may be disposed between the base of the elongate body 802 (where the elongate body 802 couples to device controller 812) and the expandable member 810. Each of the distal sensor and the proximal sensor may measure a physiologic condition of the patient, such as physiologic information indicative of blood flow through the aorta, to determine the patient's underlying physiology.
In some variations, the distal sensor 411b may be integrated proximal to the expandable 810 member while the proximal sensor 811a may be integrated distal to the expandable member 810. For example, the distal sensor 811b located on the proximal side of the expandable member 810 may be placed at a distance from the expandable member 810 such that the physiologic data collected from the distal sensor 811b may not be disrupted by the blood flow downstream of the expandable member 810. In some variations, the distal sensor 811b may be placed at a distance between about 30 mm and about 10 mm, between about 25 mm and about 15 mm, between about 22 mm and about 18 mm from the expandable member 810. For instance, the distal sensor 811b may be placed approximately 20 mm from the expandable member 810. In some variations, the proximal sensor 811a located on the distal side of the expandable member 810 may be placed between about 30 mm and about 10 mm, between about 25 mm and about 15 mm, or between about 22 mm and about 18 mm from the expandable member. For instance, the proximal sensor 811a may be placed approximately 20 mm from the expandable member 810. As discussed above, in some variations, sensors on the elongate body 402 may be situated at a specific distance from the ends of the expandable member 810 so as to acquire the physiologic data upstream and downstream of the expandable member 810.
Note that the terms “proximal” and “distal,” as used herein in relation to sensor(s) and/or particular localized blood pressure readings, refer to blood flow directionality from the heart. That is, “proximal” is closer to the heart while “distal” is further from the heart. This is not to be confused with the reversed usage of the terms when described from the perspective of a medical device such as a catheter, where the “distal end” of the medical device would commonly be understood as the end with the expandable element 810 furthest from the device controller 812 and the “proximal end” would be understood as the end closer to the operator.
In some variations, the blood flow control device may further comprise an expandable member sensor (not shown in
The blood flow control device 804 may comprise or may be coupled to one or more controllers. For example, the blood flow control device 804 may comprise a device controller 812, which may be coupled to a base of the elongate body 802. The device controller 812 may be communicatively coupled to one or more sensors, such as, for example, the proximal sensor, the distal sensor, and/or the expandable member sensor. For example, the device controller 812 may be electronically coupled to the proximal sensor, the distal sensor and/or the expandable member sensor.
A blood flow control system may comprise a system controller coupled to the blood flow control device (e.g., blood flow control device 804 in
In some variations, the device controller 2105 may further comprise a position sensor communicably coupled to a pump 2108 (further described below). In some variations, the position sensor may measure a position of a portion of the pump 2108. For instance, the position sensor may measure a position of a plunger of a syringe pump 2108. The position of the portion of the pump 2108 may be used to infer the amount of fluid that has been delivered to and/or removed from the expandable member 2110.
Additionally or alternatively, the device controller 2105 may comprise a motion sensor (e.g., encoders such as magnetic encoder, optical encoder etc.) communicably coupled to the pump. If the pump 2108 is actuated using a motor, the encoder may monitor the movement of the motor, which may be used to determine the amount of inflation and/or deflation in the expandable member 2110. In some variations, the motion sensor may be a magnetic encoder. Additionally or alternatively, the motion sensor may be an optical encoder. Additionally or alternatively, at least a portion of the system controller 2106 may comprise an optical sensor and/or a contact sensor. The optical sensor and/or contact sensor may be operably coupled to a portion of the pump 2108 to determine a position and/or to track the movement of the pump 2108. The amount of inflation and/or deflation in the expandable member 2110 may be determined based on the position and/or movement of the pump 2108. In some variations, a flow sensor may be employed to determine the amount of inflation and/or deflation in the expandable member 2110.
As depicted in
In some variations, the pump may be fluidly coupled to a valve (e.g., a stopcock valve), which may regulate the flow of fluid and/or compressed gas to the expandable member 2110. The size (e.g., volume) of the expandable member may be adjusted using the system and/or device controller 2106, 2105, and the pump 2108.
The sensors described herein may be configured to measure one or more pressures (e.g., blood pressure, expandable member pressure) in order to determine a physiologic condition or state of the patient. The controller(s) (e.g., device controller and/or system controller) communicably coupled to the sensors may be configured to receive data from the sensors that may be indicative of the physiologic condition of the patient and/or the pressure associated with the expandable member. The controller(s) may compare the received data with target data and adjust the volume of the expandable member so as to achieve the target data.
In some variations, any of the sensors described herein may be incorporated into a device and/or system configured to monitor (e.g., solely monitor, monitor without otherwise controlling blood flow) a physiologic condition or parameter of a patient, such as, for example, blood pressure, pH, a lactate level, an oxygen level, and/or a carbon dioxide level of a patient. The sensors described herein may be placed in various arteries or veins to measure a patient parameter, as mentioned above. In other instances, the sensors may measure temperature or another parameter other than blood pressure. The sensors may be placed, e.g., in the aorta, internal jugular artery, pulmonary artery, subclavian artery, femoral artery, radial artery, brachial artery, vena cava, internal jugular vein, or subclavian vein. The sensors may be included on or otherwise positioned within an elongate body (e.g., a catheter) coupled to a controller.
Any of the sensors described herein may be incorporated into a pressure measurement device. In some variations, the pressure measurement device may include a sensor within a sensor housing (as described herein), where the sensor housing is attached to, or otherwise integrated with, an elongate body (e.g., a catheter). The elongate body including the sensor within the sensor housing may be directly introduced into the vasculature to measure pressure (e.g., blood pressure), or configured for advancement through existing arterial or venous lines (e.g., vascular access lines). In some variations, the sensor may be assembled within a tubular housing (e.g., a hypotube or catheter). The sensor and tubular housing may be sized to allow passage of the elongate body into an artery or vein, or through a vascular access line. The sensor may be formed to be physically small in size, e.g., about 0.1 Fr to about 5 Fr (including all values and sub-ranges therein), and may be configured in some instances for integration into a tubular housing having a diameter ranging from about 0.1 Fr to about 10 Fr including all values and sub-ranges therein. For example, the sensor may have a size of about 0.1 Fr, about 0.2 Fr, about 0.3 Fr, about 0.4 Fr, about 0.5 Fr, about 0.6 Fr, about 0.7 Fr, about 0.8 Fr, about 0.90 Fr, about 1 Fr, about 2 Fr, about 3 Fr, about 4 Fr, or about 5 Fr. The diameter of the tubular housing may be about 0.1 Fr, about 0.2 Fr, about 0.3 Fr, about 0.4 Fr, about 0.5 Fr, about 0.6 Fr, about 0.7 Fr, about 0.8 Fr, about 0.90 Fr, about 1 Fr, about 2 Fr, about 3 Fr, about 4 Fr, about 5 Fr, about 6 Fr, about 7 Fr, about 8 Fr, about 9 Fr, or about 10 Fr. The small size of the sensor may allow space for other components of the pressure measurement device to be included in the elongate body, e.g., stiffening members, fluid lumens, etc. The size and/or diameter of the sensor and the tubular housing will generally be selected based on the diameter of the elongate body, the vascular access line through which it is to be advanced, and/or the bend angle of the artery or vein through which they are to be passed. For example, when the elongate body is about 3 Fr or 4 Fr, the diameter of the sensor and/or the tubular housing may be about 1 Fr. The length of the tubular housing may range from about 5 mm to about 15 mm, including all values and sub-ranges therein. For example, the tubular housing length may be about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about 10 mm, about 11 mm, about 12 mm, about 13 mm, about 14 mm, or about 15 mm.
The sensor housing may be attached to the elongate body of the pressure measurement device in various ways. For example, the sensor housing may be attached using one or more structural components, as previously described. The sensor and structural component(s) may form a sensor assembly. For instance, as shown in
The sensors used in the pressure measurement devices may be connected to a printed circuit board assembly (PCBA) housing via one or more wires coupled to the sensor and one or more pins on the PCBA. For example, referring to
The PCBA housing may be configured to connect with a controller (e.g., a controller of a blood flow control system) and may include a PCBA network configured to control one or more functions of the sensor. The PCBA housing may comprise a top portion and a bottom portion. The top and bottom portions may be connected via a hinge or an adhesive, or may be attached by snap-fit, friction fit, etc. The adhesive may be tape (e.g., foam tape) on one or more areas on the bottom portion of the housing. Any suitable adhesive may be employed. Referring to
Although the foregoing variations have, for the purposes of clarity and understanding, been described in some detail by illustration and example, it will be apparent that certain changes and modifications may be practiced, and are intended to fall within the scope of the appended claims. Additionally, it should be understood that the components and characteristics of the systems and devices described herein may be used in any combination. The description of certain elements or characteristics with respect to a specific figure are not intended to be limiting or nor should they be interpreted to suggest that the element cannot be used in combination with any of the other described elements. For all of the variations described herein, the steps of the methods may not be performed sequentially. Some steps are optional such that every step of the methods may not be performed.
This application claims priority to U.S. Provisional Application No. 63/604,163, filed on Nov. 29, 2023, which is hereby incorporated by reference in its entirety.
This invention was made with government support under grant W81XWH-22-C-0044 awarded by the Joint Warfighter Medical Research Program and Congressionally Directed Medical Research Programs. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63604163 | Nov 2023 | US |
