Patent Application
20240342484
The present disclosure relates to implantable devices, and, in particular, to techniques for transmitting data wirelessly between implantable magnetoelectric devices.
Wireless implantable bioelectronics provide hope for revolutionary clinical therapies, such as treating neurological and psychiatric disorders by interfering directly with the nervous system. These devices can deliver controlled stimulation to modulate the electrical activities of the nervous system and/or record electrical, chemical, and physical properties for better diagnosis.
One challenge in the design of wireless bio-implants is to reliably power and communicate with miniaturized implants. While batteries have been the conventional power source of medical implants for a long time, the last decade has seen a transition to wireless power transfer solutions that feature smaller footprints, less weight, longer lifetime, and less invasive implantation procedures. Various wireless power transfer technologies (e.g., including radio frequency (RF), inductive coupling, ultrasound, and light) have demonstrated the ability to wirelessly power medical implants. However, these wireless power transfer technologies face trade-offs between receiver size and misalignment tolerance, transmission loss, and/or power that can safely be delivered through the biological tissues. Accordingly, improvements for miniaturized wireless bio-implants for advanced biomedical applications like closed-loop neuromodulation are desirable.
In some embodiments, a system is provided. The system can include an implantable device that includes a magnetoelectric film, an electrical circuit coupled to the magnetoelectric film, and one or more electrodes. The system can also include a base station that includes a magnetic field generator and a magnetic transceiver. The system can also include one or more sensors that are physically connected or wirelessly connected to the base station. For example, a sensor of the one or more sensors may be physically connected to the implantable device and may be wirelessly connected to the base station (e.g., via one or more components of the implantable device, such as the magnetic field generator and/or the magnetic transceiver).
In some embodiments, the base station further includes electronics configured to record one or more stimulation times at which the implantable device delivers stimulation to a target tissue, access a physiological signal collected by the one or more sensors, identify one or more select portions of the physiological signal, where each portion has a start time corresponding to a stimulation time of the one or more stimulation times, facilitate a prediction of, based on the one or more select portions, whether or a degree to which an implant stimulation protocol is resulting in a target effect, and facilitate a modification of the implant stimulation protocol based on the prediction. The predicting of whether or the degree to which an implant stimulation protocol may be performed using the electronics, may be performed automatically, and/or may be performed in response to input received from a user of a computing system (e.g., to which one or more signals, results, recommendations, disclosed result(s), and/or disclosed output(s) are received and/or output.
In some embodiments, modifying the implant stimulation protocol can include setting a new schedule as to when the implantable device delivers stimulation.
In some embodiments, modifying the implant stimulation protocol can include identifying a new intensity for stimulation that is generated by the implantable device.
In some embodiments, the electronics can be further configured to access a secondary signal collected by an input component of the base station and identify one or more select portions of the secondary signal. Each portion has a start time relative to a stimulation time of the one or more stimulation times. The prediction of whether or the degree to which the implant stimulation protocol is resulting in the target effect can be further based on the one or more secondary select portions.
In some embodiments, the secondary signal was generated based on backscattering of a magnetic field applied by the magnetic field generator of the base station.
In some embodiments, the system includes a wearable component that includes the base station and the one or more sensors.
In some embodiments, the wearable component is configured to be worn on a head of a user.
In some embodiments, the wearable component is configured to be worn on around a waist of a user.
In some embodiments, the wearable component is configured to be worn on around a neck of a user.
In some embodiments, the one or more sensors includes at least one electroencephalography (EEG) electrode.
In some embodiments, the one or more sensors include a heart-rate monitor, an accelerometer, and/or an optode.
In some embodiments, the electrical circuit can further include a resonant frequency modulator configured to modulate the resonant frequency of the magnetoelectric film by applying different electric loading conditions that change a property of the magnetoelectric film.
In some embodiments, the implantable device can be configured to detect an activation field and establish a bi-directional communication link with the base station when the base station is positioned proximate to the implantable device.
In some embodiments, a method is provided. The method can involve sending, by electronics of a base station including a magnetic field generator and a magnetic transceiver, instructions including an implant stimulation protocol to an implantable device for delivering stimulation to a target tissue at one or more stimulation times. The implantable device includes a magnetoelectric film, an electric circuit coupled to the magnetoelectric film, and one or more electrodes. The method can further involve recording the one or more stimulation times at which the implantable device delivers the stimulation to the target tissue, accessing a physiological signal collected by one or more sensors that are physically connected or wirelessly connected to the base station, identifying one or more select portions of the physiological signal, where each portion has a start time corresponding to a stimulation time of the one or more stimulation times, facilitating a prediction of, based on the one or more select portions, whether or a degree to which the implant stimulation protocol is resulting in a target effect, and facilitate a modification of the implant stimulation protocol based on the prediction.
In some embodiments, modifying the implant stimulation protocol includes setting a new schedule as to when the implantable device delivers stimulation.
In some embodiments, modifying the implant stimulation protocol includes identifying a new intensity for stimulation that is generated by the implantable device.
In some embodiments, the method further involves accessing a secondary signal collected by an input component of the base station and identifying one or more secondary select portions of the secondary signal. Each secondary select portion has a start time relative to a stimulation time of the one or more stimulation times. The prediction of whether or the degree to which the implant stimulation protocol is resulting in the target effect can be further based on the one or more secondary select portions.
In some embodiments, the secondary signal was generated based on backscattering of a magnetic field applied by the magnetic field generator of the base station.
In some embodiments, the one or more sensors includes at least one electroencephalography (EEG) electrode.
In some embodiments, the one or more sensors includes a heart-rate monitor, an accelerometer, and/or an optode.
In some embodiments, the method further involves modulating, by a resonant frequency modulator of the base station, a resonant frequency of the magnetoelectric film by applying different electric loading conditions that change a property of the magnetoelectric film.
In some embodiments, the implantable device is configured to detect an activation field and establish a bi-directional communication link with the base station when the base station is positioned proximate to the implantable device.
In some embodiments, the method further involves accessing a diagnostic signal of the implantable device during the one or more stimulation times at which the implantable device delivers the stimulation to the target tissue and modifying the implant stimulation based on the diagnostic signal.
In some embodiments, a method is provided. The method can involve sending, by electronics of a base station including a magnetic field generator and a magnetic transceiver, instructions including an implant stimulation protocol to a first implantable device for delivering stimulation to a target tissue at one or more stimulation times. The first implantable device includes a first magnetoelectric film, a first electric circuit coupled to the first magnetoelectric film, and one or more first electrodes. The method involves recording, by a second implantable device, the one or more stimulation times at which the first implantable device delivers the stimulation to the target tissue. The second implantable device includes a second magnetoelectric film, a second electric circuit coupled to the second magnetoelectric film, and one or more second electrodes. The method involves accessing a physiological signal collected by one or more sensors that are physically connected or wirelessly connected to the base station, identifying one or more select portions of the physiological signal, where each portion has a start time corresponding to a stimulation time of the one or more stimulation times, facilitate a prediction of, based on the one or more select portions, whether or a degree to which the implant stimulation protocol is resulting in a target effect, and facilitate a modification of the implant stimulation protocol based on the prediction.
Some embodiments of the present disclosure include a system including one or more data processors. The system can further include a non-transitory computer readable storage medium containing instructions which, when executed on the one or more data processors, cause the one or more data processors to perform part or all of one or more of the methods disclosed herein.
In some embodiments, a computer-program product is provided that is tangibly embodied in a non-transitory machine-readable storage medium. The computer-program product can include instructions configured to cause one or more data processors to perform part or all of one or more of the methods disclosed herein.
The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.
Aspects and features of the various embodiments will be more apparent by describing examples with reference to the accompanying drawings, in which:
In the appended figures, similar components and/or features can have the same reference label. Further, various components of the same type can be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
While certain embodiments are described, these embodiments are presented by way of example only, and are not intended to limit the scope of protection. The apparatuses, methods, and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and changes in the form of the example methods and systems described herein may be made without departing from the scope of protection.
Implantable devices can be used to provide stimulation to the brain, or other nervous system regions, of subjects. The stimulations may be used (for example) to treat a medical condition (e.g., a neurological or psychiatric disorder) or a symptom. These implantable devices are typically on the mm-scale and usually require carrier frequencies of more than a GHz. Unfortunately, stimulation at such high carrier frequencies can increase the possibility of the body not responding to the stimulation. Inductive coupling has been used in wireless implantable systems because of its flexible capability for charging and bi-directional telemetry. However, the coupling is sensitive to the variations in distance and direction, especially when the implant coil is small. Additionally, most inductively powered devices work at 13.56 MHz or higher frequencies for better power transmission efficiency, but such a frequency can result in substantial energy being absorbed by the body, which may be undesirable. As a result, inductively powered devices may be required to operate under certain restrictions, such as time restrictions for how often and how long these devices can be operated at a particular frequency within a particular time period. While ultrasound and optics have shown potentials in wirelessly transmitting power and data, they suffer from energy loss due to reflection or scattering when transferring through different tissue layers, limiting their efficiency.
Embodiments of the present disclosure utilize magnetoelectric power for wirelessly powering mm-sized devices implanted deep inside the body by converting low-frequency (e.g., hundreds of kHz) magnetic fields to electric voltage using magnetoelectric transducers. Systems and methods that use magnetoelectric power results in several advantages (e.g., relative to RF, inductive coupling, ultrasound, and light power transfer techniques) including high power transmission efficiency with miniaturized size, high power delivery (e.g., greater than 1 mW), and high misalignment tolerance (e.g., angle offset and lateral offset) relative to inductive coupling and ultrasound power transfer devices. These features are empowered by using magnetoelectric materials that have sufficient power density, mechanical resonance frequency, and permeability to concentrate magnetic flux inside the material. First, the magnetoelectric transducer's voltage coefficient is independent of the transducer's width and length. As a result, the magnetoelectric effects can support miniaturization of an implantable device while maintaining a power transfer efficiency that is higher than the power transfer efficiency of radio frequency, inductive coupling, and ultrasound power transfer devices. In addition, the permeability of magnetostrictive materials can result in significant concentration of magnetic flux, which enhances the magnetoelectric power transfer's robustness to misalignment. Magnetoelectric communication is also less sensitive to angles and lateral offsets than ultrasound-based wireless transfers that require focused sound waves. Additionally, the sub-MHz low resonance frequency of magnetoelectric leads to lower tissue absorption, and a stronger magnetic field is allowed without violating safety limits. The use of magnetoelectric power results in an order-of-magnitude higher power that can be safely delivered to the implants deep inside the body compared to high-frequency inductive coupling or RF. Specifically, a magnetoelectric implantable device working at the 335-kHz resonance frequency may be able to receive a peak power of 3.8 mW at 3 cm under electromagnetic exposure limits, which is equivalent to 0.4 mW for the 13.56-MHz inductive coupling counterpart.
In some embodiments, the implantable device can include a magnetoelectric film that acts as a transducer, an electrical circuit (e.g., an application-specific integrated circuit (ASIC) chip), and one or more electrodes. A base station in communication with the implantable device can provide wireless power transfer and data downlink communication to the implantable device. Sharing the same magnetoelectric mechanism for wireless power and communication can facilitate miniaturization of the implantable device and improve power transfer efficiency and data transfer efficiency. The base station can include a magnetic field generator that acts as a magnetoelectric transmitter to the implantable device to digitally program stimulation parameters of an implant stimulation protocol. Uplink communications may be useful for the implantable device to report sensor data for closed-loop applications and to monitor and calibrate operation conditions of the implantable device. Magnetoelectric backscatter can be used to send data from the implantable device to a magnetic transceiver of the base station. One or more sensors (e.g., electroencephalogram (EEG) electrodes, heart-rate monitors, accelerometers, or optodes such as functional near-infrared spectroscopy (fNIRS) sensors) can also be physically connected or wirelessly connected to the base station for monitoring physiological conditions of a user. In some instances, a sensor of the one or more sensors is an electronic biopotential sensor, which may be part of or physically connected with and/or part of the implantable device.
Physiological signals generated, captured and/or communicated by the sensors, and optionally from the implantable device, may be used to predict whether or a degree to which the implant stimulation protocol is resulting in a target effect. The implant stimulation protocol may then be modified based on the prediction (e.g., based on rules defining stimulation parameters that are associated with particular values for variables of the physiological signal and/or the signal generated by the implantable device). Accordingly, the implantable device and the base station can have bi-directional communication that allows for tuning of stimulation parameters based on a user's response to a particular implant stimulation protocol.
The magnetoelectric film of the implantable device 110 can be fabricated using a bilayer or trilayer sheet including one or more magnetostrictive layers and one or more piezoelectric layers. In an example, the magnetostrictive layer can use 27-μm Metglas, and the piezoelectric layer can use 254-μm-thick lead zirconium titanate PZT-5 material. When the transmitter coil 122 applies an external magnetic field, mechanical vibrations are generated in the magnetostrictive layer due to the Joule effect. Since the magnetostrictive layer and the piezoelectric layer are mechanically coupled, these vibrations are transferred to the piezoelectric layer to create an electric potential across the magnetoelectric film due to the direct piezoelectric effect.
The vibrations generated in the magnetostrictive layer result in a change in the material magnetization due to the Villari effect. This change can be seen as a backscattered field generated by the magnetoelectric film. Hence, utilizing these echoes as backscattered signals can enable uplink data transfer from the implantable device 110 to the pick-up coil 124. During the on-time of the applied magnetic field, the magnetoelectric materials vibrate at the applied field frequency. Since the generated backscattered field may oscillate at the same excitation frequency, it may be challenging to decouple the applied field frequency signal from the backscattered signal. To isolate the response of the magnetoelectric film, the backscattered field can be measuring during a ring-down period when the excitation field is off. Over the ring-down period, the magnetoelectric film dissipates the stored mechanical energy in the form of decaying voltage at its mechanical resonance frequency irrespective of the excitation field frequency.
In some examples, characteristics of the backscattered field can be changed at the implantable device 210 to modulate the backscattered signal for transmitting data. Although the backscattered field is generated by the magnetostrictive layer, modulating the characteristics of either the piezoelectric layer, magnetostrictive layer, or both can affect the backscattered field due to the mechanical coupling of the layers. The modulation of the backscattered field can be done by controlling the effective mechanical, magnetic, or electric properties of the composite. In an example, the magnetostrictive materials can be coated with a thin layer of stimuli-responsive polymers that respond to external stimuli by shifting the overall mass and mechanically modulating the resonance frequency of the magnetoelectric film. The resonant frequency modulator can modulate the resonant frequency of the magnetoelectric film by applying different electrical loading conditions that change a property of the magnetoelectric film. In some instances, an electric loading modulation technique can be used to tune the characteristics of the backscattered field. The electric load can be either an active load (e.g., a direct current (DC) biasing voltage) or a passive load (e.g., inductive, resistive, capacitive, or a combination thereof). Using passive loads may enable a miniaturized footprint of the implantable device 110 and limit constraints on the power budget.
Changing the capacitive or resistive loads across the magnetoelectric film can change the voltage across the magnetic film as well as its resonance frequency. Consequently, the amplitude and frequency of the backscattered field during the ring-down period are changed. Since a frequency shift may be more immune to the depth variation and misalignment that often occur during implantation of an implantable device, frequency modulation can be used to encode uplink data of the implantable device 110.
Capacitive load-shift-keying (LSK) modulation can result in a large frequency shift and small voltage drop to help resolve the frequency difference at the pick-up coil 124 and to improve the signal-to-noise ratio (SNR). The LSK-induced frequency-shift keying (FSK) can be used to digitally encode the data by switching between two load conditions: an open circuit and a capacitive load. To determine the suitable capacitive load to be implemented on the ASIC chip, the resonance frequency of the magnetoelectric film can be measured while connected in parallel to different capacitive loads and compared with that a mathematical model for validation.
The base station 220 can include electronics for controlling and monitoring stimulation provided to the user by the implantable device 210. The base station 220 may power and communicate with the implantable device 210 using magnetoelectric techniques, as described in
Although not illustrated in
In some examples, multiple implantable devices may be implanted into the brain of the user. Each implantable device may be associated with a different implant stimulation or recording protocol. So, a first implantable device may execute a first implant stimulation protocol of an amplitude of 1.5 V with a mono-phasic shape and a pulse width of 0.5 ms at a frequency of 50 Hz, while a second implantable device executes a second implant stimulation protocol of an amplitude of 1.5 V with a mono-phasic shape and a pulse width of 0.5 ms at a frequency of 100 Hz. Alternatively, a first implantable device may be used to deliver stimulation according to the implant stimulation protocol, whereas a second implantable device may be used to record during the stimulation times of the first implantable device.
Each of the implantable devices may transmit data back to the base station 220. The data uplink may be in the form of a magnetic field generated by each of the implantable devices oscillating at a resonant frequency of the implantable device. The implantable devices can emit electrical signals with different timings or frequencies such that the signals constructively interfere to stimulate the target region. The interference may be created by an overlap between alternating electric fields at the same frequency produced by the multiple implantable devices. Alternatively, the interference may be created by the overlap between alternating electric fields of different frequencies produced by the multiple implantable devices.
In some instances, each implantable device may be controlled by a separate base station. Alternatively, each implantable device may be associated with a unique digital identifier that the base station 220 can use to communicate with the desired implantable device. The unique digital identifier can be a bit sequence in front of a signal. So, the base station 220 can send instructions for the different implant stimulation protocols to the implantable device 210 and additional implantable devices with the appropriate digital identifiers. As an example, the base station 220 can send instructions of the implant stimulation protocol for the implantable device 210 with the unique digital identifier of the implantable device 210. The base station 220 can also send instructions of other implant stimulation protocols for other implantable devices with other digital identifiers. Each of the implantable devices may receive each of the instructions, but may only process and execute the instructions with their corresponding digital identifier. The interference may be produced by controlling a relative timing of the electrical field produced by the implantable devices. So, the implantable device 210 may be instructed to deliver stimulation 10 ms from receiving the instructions and another implantable device may be instructed to deliver stimulation 20 ms from receiving the instructions.
In some examples, the electronics accesses a physiological signal collected by the sensors 230, which may be electrical sensors or optical sensors. For instance, the sensors 230 may be EEG electrodes or optodes (e.g., fNIRS sensors). The physiological signal collected can be based on the type of sensors. For instance, EEG electrodes may measure electrical activity (e.g., beta-band frequency), fNIRS sensors may measure changes in blood flow or oxygenation, accelerometers may measure tremor or seizure activity. The electronics can process the physiological features and/or can facilitate determining whether to record physiological signals, when to record physiological signals and/or how to align physiological signals (e.g., by defining event times that are or may be used for subsequent alignment). Such processing may include (for example) identifying portions of the physiological signal that have a start time corresponding to a stimulation time of the stimulation times at which the implantable device 210 delivers the stimulation. For example, the electronics may determine the start times of the stimulations based on the implant stimulation protocol and then detect the portions of the physiological signal that correspond to the start times. For example, the stimulation may be timed to start according to the phase of the user's natural brain oscillation (e.g., theta band oscillations) as measured by the external EEG or the implantable device 210. As another example, based on the portions of the physiological signal, the electronics can predict whether or a degree to which the implant stimulation protocol is resulting in a target effect. In the case of Parkinson's, the target effect may be a reduction of tremors (e.g., as detected using an accelerometer in a user device) or a reduction in beta band activity (e.g., as detected using a sensor within or connected to the implantable device or in another implantable device or external sensor—such as an EEG device). A particular physiological status (e.g., neural activity, oxygenation level, etc.) may be indicative of the implant stimulation protocol resulting in the target effect. So, if the portions of the physiological signal indicate the particular physiological status for the user, the electronics can determine that the implant stimulation protocol is resulting in the target effect.
The electronics can then modify the implant stimulation protocol based on the prediction of whether or the degree to which the implant stimulation protocol results in the target effect. For instance, a new schedule may be set for when the implantable device 210 delivers the stimulation. The new schedule may be that, rather than stimulation being delivered for one minute at ten-minute intervals, the stimulation is to be delivered for thirty seconds at ten-minute intervals. Additionally or alternatively, modifying the implant stimulation protocol may involve identifying a new intensity for the stimulation that is generated by the implantable device 210. For example, the amplitude may be adjusted from 1.0 V to 2.3 V.
The electronics may determine the implant stimulation protocol or modifications for the implant stimulation profile based on one or more rules. For instance, rules may be configured to include one or more if/then assessments, an equation that calculates one or more stimulation parameters based on variables of the physiological signal or the implant signal, etc. As an example, the if/then assessments may specify that if the physiological signal indicates first neural activity, then the implant stimulation protocol should include an amplitude of 1.0 V, whereas if the physiological signal indicates second neural activity, then the implant stimulation protocol should include an amplitude of 2.3 V. For example, if the stimulus is not generating sufficient changes in the positive or negative local field potential (LFP) or EEG signals following the stimulus, the amplitude can be increased to recruit a stronger neural response. The equation can receive the physiological signal, the implant signal, and/or additional variables and calculate the stimulation parameters. The rules may be defined at least in part by a care physician or other provider.
In an example, the electronics may additionally access a secondary signal collected by an input component of the base station 220. The input component may be a magnetic transceiver or another component. The secondary signal may be generated based on magnetoelectric backscattering, or other uplink modalities, as previously described in
The electronics may additionally or alternatively access a diagnostic signal of the implantable device during the one or more stimulation times at which the implantable device 210 delivers the stimulation to the target tissue. The diagnostic signal may indicate one or more properties of the implantable device 210. For instance, the diagnostic signal may indicate an impedance of the electrodes of the implantable device 210. The prediction of whether or the degree to which the implant stimulation protocol is resulting in the target effect can be further based on the diagnostic signal. So, the implant stimulation protocol may be modified based on the prediction associated with the diagnostic signal. As an example, if the diagnostic signal indicates that the impedance of the electrodes changes, the implant stimulation protocol may be modified to increase the amplitude of the stimulation.
In an example, the implantable device 310 can be used to stimulate afferent and efferent peripheral nerve targets in the abdominal cavity of the user to deliver therapeutic stimulation to elicit target organ function or block or modify disease-causing communication from the target organ to the central nervous system. Due to the small size of the implantable device 310, the risk of bowel perforation may be reduced by using the implantable device 310 compared to other implantable devices that use alternate power transfer techniques (e.g., inductive coupling, ultrasound, light, etc.). Peripheral nerves may be stimulated to control insulin function, bile production, stomach fullness and appetite indicators, bladder control, bowel control, sexual function, etc.
The base station 320 can include electronics for controlling and monitoring stimulation provided to the user by the implantable device 310, similar to the base station 220 in
In an example, the electrical circuit includes a power management module that interfaces with the magnetoelectric film for energy harvesting and generates supply voltages for the electronics. Alternating current (AC) voltage induced on the magnetoelectric film can be rectified to a DC voltage by an active rectifier. Then the DC voltage can be regulated by a switched-capacitor DC-DC power converter to provide supply voltage for a voltage reference generator and a low-dropout regulator (LDO). The DC-DC converter also charges the off-chip capacitor to buffer energy for high-power stimulation. A constant supply voltage (e.g., 1 V) may be generated by the LDO for low-power digital circuitry.
The implantable device 410 can receive downlink data simultaneously with magnetoelectric power from a base station. Since simultaneous power and data transfers may be constrained by the tradeoff between the power transfer efficiency and bandwidth of the transducer, the downlink data can be modulated by a time-domain scheme, in which multiple bits are encoded into the duration of a single pulse to amortize the low switching speed of the transducer. The data from the base station can be recovered by the electrical circuit through a time-to-digital converter to program its operation and stimulation parameters.
In a particular example, the electrical circuit may sense an implant-received voltage for operation regulation and temperature for in-body thermal monitoring. The voltage sensing can be performed by an 8-bit analog-to-digital converter whose core is a voltage-controlled oscillator (VCO). The VCO's output frequency can lineally change with the implant input voltage. A 16-bit temperature sensor can be implemented by a low power ring-oscillator with a native transistor for local voltage regulation. The temperature sensor can leverage subthreshold oscillation dependence for temperature monitoring with 10-nW power consumption.
An uplink module can transmit the voltage and temperature sensor data to the base station through magnetoelectric backscatter. The electrical circuit modulates the capacitive load on the magnetoelectric film to shift the frequency of the backscattered signal. The uplink module may not include any active-radio components, so its power consumption may be negligible (e.g., <5 nW).
The voltage-controlled stimulation pulses can be generated by a stimulation driver and delivered through the electrodes to target tissue. The stimulation may be performed as an implant stimulation protocol with fully programmable parameters, including amplitude (e.g., 0.2 to 3.5 V, 4 bits), shape (e.g., bi-phasic or mono-phasic), pulse width (e.g., 0.05 to 1.5 ms, 3 bits), and frequency (e.g., 0 to 200 Hz).
A magnetic field generator of the base station 620 can include a power amplifier based on an H-bridge that injects AC current into the transmitter coil to produce a magnetic field. In an example, the magnetic field may be 335 kHz. In the backscatter receiver, an analog frontend (AFE) amplifies the magnetoelectric backscattered signal in the pick-up coil and generates recovered pulses for the digital backend for data demodulation. The controller of the magnetic transceiver can control the operations of the base station 620 and the implantable device. To power the implantable device, the controller turns on the power amplifier to apply the alternating magnetic field. By disabling the power amplifier in a short time, the controller generates magnetic field notches to switch the functions of the implantable device, such as communication, sensing, and stimulation. Accordingly, all the components in the system can be synchronized.
In some embodiments, the power amplifier and the AFE can be built with electronic components soldered on printed circuit boards. The data demodulation backend circuit and the control module may be implemented by field programmable gate arrays (FPGA). The AFE for amplification and digitization can be built with an analog multiplexer, an active low-pass filter (LPF), a low-noise instrumentation amplifier, and a high-speed comparator. The voltage of the pick-up coil can be high in the power transfer phase due to strong inductive coupling to the transmitter coil. Thus, the AFE can use a multiplexer with high-voltage tolerance in the input stage to block the input voltage when the applied magnetic field is on. The analog multiplexer can be turned on during the uplink data transmission to pass the backscattered signal sensed by the pick-up coil. High-frequency noise and interference can be filtered out by the LPF, which may use a 375-kHz bandwidth, whose output is amplified by the instrumentation amplifier with a gain of a certain amount (e.g., 60 dB). The comparator can convert the output of the amplifier to a train of digital pulses, whose frequency is substantially similar to the magnetoelectric backscattered field.
The digital backend of the backscatter receiver can employ frequency-to-digital conversion for uplink data demodulation. The digital backend can use several pulses of the output of the AFE to build the demodulation window, transforming the LSK-induced frequency shift a duration of time between the Nith and the Nith AFE output pulse. In an example, Ni can be nine and Nj can be eighteen. A counter can be used to count the number of FPGA clocks in the demodulation window to compute the duration. When the magnetoelectric transducer is connected with a capacitor, the backscattered signal's frequency decreases, resulting in a longer time between the Nith and the Nith AFE output pulse. Hence, by comparing the duration with a predefined threshold, LSK-modulated bits “1” and “0” can be recovered. For example, the predefined threshold may be 27 μs, and the digital backend may determine the length of time it takes for nine frequency pulses. If the nine frequency pulses occur in the backscattered signal data in less than 27 μs, the bit can be set to “0” for the demodulation window, and if the nine frequency pulses occur in the backscattered signal data in more than 27 μs, the bit can be set to “1” for the demodulation window.
At block 702, the base station sends instructions including an implant stimulation protocol to an implantable device for delivering stimulation to a target tissue. The implantable device can be implanted in a brain or at a nerve of a user. The implantable device can include a magnetoelectric film, an electrical circuit coupled to the magnetoelectric film, and one or more electrodes. The implant stimulation protocol may be a default implant stimulation protocol, or the base station may receive an indication of the implant stimulation protocol from a user device associated with a clinician, the user, or other personnel. The implant stimulation protocol may specify an amplitude, frequency, pulse width, shape, etc. of the stimulation that is to be delivered by the implantable device. Upon receiving the instructions, the implantable device can deliver stimulation to the target tissue according to the implant stimulation protocol.
At block 704, the base station records one or more stimulation times at which the implantable device delivers the stimulation to the target tissue. The one or more stimulation times can be indicated in the implant stimulation protocol. So, based on the instructions sent to the implantable device, the base station can record the stimulation times.
At block 706, the base station accesses a physiological signal collected by one or more sensors physically connected or wirelessly connected to the base station. The sensors may be (for example) EEG electrodes, optodes, other signals disclosed herein. At least one of the one or more sensors can be part of a wearable component (e.g., worn around a head, neck, or waist of the user) that also includes the base station. Alternatively or additionally, at least one of the one or more sensors may be connected with, physically attached to and/or part of the implantable device. Each of the one or more sensors can continuously or periodically generate the physiological signal while the base station is proximate the implantable device. So, the physiological signal may include portions during the stimulation delivered by the implantable device and portions when the implantable device does not deliver stimulation. It will be appreciated that a sampling frequency and/or a trigger for sampling may be consistent across multiple or all sensors and/or may differ across at least two (or across all) of the one or more sensors.
At block 708, the base station identifies select portions of the physiological signal. Each portion of the select portions can have a start time corresponding to a stimulation time of the one or more stimulation times. So, the base station can identify start times of the stimulation times based on the implant stimulation protocol and determine which portions of the physiological signal correspond to the start times.
At block 710, the base station facilitates predicting, based on the select portions, whether or a degree to which the implant stimulation protocol is resulting in a target effect. The prediction may be performed by or at the base station, may be performed by or at the implant, may be performed by or at an external device, or may be received from an external device (e.g., a device associated with a caregiver or physician). A particular physiological status (e.g., neural activity, oxygenation level, etc.) indicated by the select portions of the physiological signal may be indicative of the implant stimulation protocol resulting in the target effect. So, if the select portions of the physiological signal indicate the particular physiological status for the user, it can be determined or inferred that the implant stimulation protocol is resulting in the target effect. Otherwise, it can determined or inferred that the implant stimulation protocol is not resulting in the target effect and should be modified.
At block 712, the base station facilitates modifying the implant stimulation protocol based on the prediction. The modification may be identified and/or triggered by or at the base station, may be identified and/or triggered by or at the implant, may be identified and/or triggered by or at an external device, or may be received from and/or triggered by an external device (e.g., a device associated with a care giver or physician). The implant stimulation protocol may be modified based on an input received from the user device associated with a clinician, the user, or other personnel. The input can include an indication of one or more updated stimulation parameters for the implant stimulation protocol. For instance, a new schedule may be set for when the implantable device delivers the stimulation. Additionally or alternatively, the intensity for the stimulation that is generated by the implantable device may be modified. The implant stimulation protocol can also be modified based on a secondary signal that is generated by the implantable device based on backscattering of the stimulation. Portions of the secondary signal that have a start time relative to a stimulation time of the implantable device may be identified and the prediction of whether or the degree to which the implant stimulation protocol is resulting in the target effect can be further based on the portions of the secondary signal.
Some embodiments of the present disclosure include a system including one or more data processors. In some embodiments, the system includes a non-transitory computer readable storage medium containing instructions which, when executed on the one or more data processors, cause the one or more data processors to perform part or all of one or more methods and/or part or all of one or more processes disclosed herein. Some embodiments of the present disclosure include a computer-program product tangibly embodied in a non-transitory machine-readable storage medium, including instructions configured to cause one or more data processors to perform part or all of one or more methods and/or part or all of one or more processes disclosed herein.
The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention as claimed has been specifically disclosed by embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.
The ensuing description provides preferred exemplary embodiments only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the preferred exemplary embodiments will provide those skilled in the art with an enabling description for implementing various embodiments. It is understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims.
Specific details are given in the following description to provide a thorough understanding of the embodiments. However, it will be understood that the embodiments may be practiced without these specific details. For example, circuits, systems, networks, processes, and other components may be shown as components in block diagram form in order not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.
This application claims priority to U.S. Provisional Patent Application No. 63/459,360, filed on Apr. 14, 2023, titled “WIRELESS MONITORING AND CONTROL OF IMPLANTABLE MAGNETOELECTRIC DEVICES”, which is incorporated by reference in its entirety for all purposes.
This invention was made with government support under Grant No. ECCS-2023849 awarded by the National Science Foundation and Grant No. FA8650-21-2-7110 awarded by the Air Force Research Laboratory. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63459360 | Apr 2023 | US |
