The invention relates to sensors and, in particular, to flexible sensors.
As a result of advances in miniaturization and device integration, it is now possible to have wearable sensors that provide data about the wearer more or less continuously or on demand. These sensors can be worn outside the body, in which case they are often called “smart wearable systems.” They can also be worn inside the body. In such cases, they are often called “implantable diagnostic devices.”
The devices themselves are typically integrated into a two-dimensional manifold. In some cases, the manifold is a rigid planar structure, in which case devices cannot move relative to each other. However, in many cases, the devices are integrated into a flexible two-dimensional manifold. Smart clothing, in which devices are disposed on a flexible fabric, provides an example of this.
In one aspect, the invention features an article of manufacture that includes a sensor for sensing a characteristic of a measurement region. Such a sensor includes first and second threads, with the second including a semiconductor, a dielectric that capacitively couples the first and second threads at a coupling region, and a sensing electrode that is configured to engage in an interaction with the measurement region, the interaction causing a change in an electrical characteristic of the sensing electrode and that is also in electrical communication with one of the first and second threads.
Among the embodiments of such a sensor are those in which the sensing electrode is integral with the first thread and those in which it is integral with the second thread.
In some embodiments, the sensor electrode is integral with the first thread and, in operation, an electric field modulates a current on the second thread. This electric field results from interaction of the sensor electrode with the measurement region. Among these are embodiments that also include a third thread that is capacitively coupled with the second thread. In such embodiments, an interaction of the sensor electrode with the measurement region causes a perturbation of an electric field caused by a potential applied between the first and third threads. This perturbation modulates a current on the second thread.
In still other embodiments, the sensor electrode is disposed along a current path that includes the second thread. In operation, a change in an electrical property of the sensor electrode as a result of having interacted with the measurement region modulates a current along this current path.
Also among the embodiments are those in which a loop connects to the first thread. This loop encircles the second thread in the coupling region.
Also among the embodiments of the sensor are those in which conductors connect to measurement instrumentation. These include embodiments in which first and second wires knotted around the second thread connect to measurement instrumentation for sensing current in the second thread. These also include embodiments in which third and fourth threads connected to the second thread connect to measurement instrumentation for sensing current in the second thread.
Also among the embodiments are those that include first and second conducting paths connected to the second thread. In these embodiments, the sensor electrode is in electrical communication with the second thread through first conducting path. When the sensor is operational, the second path connects to measurement instrumentation.
Embodiments further include those in which the sensor is one of many sensors that are part of a sensor fabric. In some of these embodiments, the sensors are of different kinds. The sensors are multiplexed such that an output of the sensor fabric corresponds to an output of a selected one of the sensors that comprise the sensor fabric. In others, for each sensor in the plurality, there exists a distance between a coupling region of the sensor and a sensor electrode for the sensor. These distances differ among the sensors that comprise the sensor fabric. Among these embodiments are those in which the sensors are of the same kind and those in which they are different kinds. These sensor fabrics can thus either measure the same parameter at different locations or measure different parameters at the same location.
In some embodiments, the sensor is one of a plurality of sensors in a sensor fabric. Each of these sensors also includes a first thread, a second thread that defines a semiconducting portion of a current path, a dielectric that capacitively couples the first and second threads, and a sensing electrode that is along the current path. Each of the sensing electrodes in the sensor fabric is configured to interact with a measurement region. This interaction causes a change in an electrical characteristic of the sensing electrode. Each conducting path has first and second ends, the latter being shorted together. Signals on each of the first threads cause all but one of the conducting paths to be in a non-conducting state. As a result, an output of the sensor fabric represents a measurement made by a selected one of the sensing electrodes.
Other embodiments of the article of manufacture feature a selection module and a sensor fabric including a plurality of sensors, among which is the sensor. Each of these sensors includes a first thread, a second thread that defines a semiconducting portion of a current path, a dielectric that capacitively couples the first and second threads, and a sensing electrode that is along the first thread. Each of the sensing electrodes is configured to interact with a measurement region. This interaction causes a change in an electrical characteristic of the sensing electrode. Each conducting path includes first and second ends, with the second ends being shorted together. The selection module includes transistors, each of which connects to a conducting path of a selected one of the sensors. Signals on each of the transistors in the selection module cause all but one of the conducting paths to be in a non-conducting state. As a result, an output of the sensor fabric represents a measurement made by a selected one of the sensing electrodes.
Some embodiments of the article manufacture carry out Boolean logic functions. Such embodiments include a sensor fabric including a plurality of sensors, among which is the sensor. Among these sensors are sensors that are members of a set of sensors that have been interconnected to form a logic gate. Each of the sensors that are members of the set includes first and second threads capacitively coupled by the dielectric, the second thread defining a semiconducting current path.
Some embodiments of the article manufacture carry out analog computation. Such embodiments include a sensor fabric including a plurality of sensors, among which is the sensor, Each of the sensors includes capacitively coupled first and second threads and a sensor electrode along the second thread, the second thread defining a semiconducting current path. Among the sensors in the fabric are sensors that are members of a set of sensors that have been interconnected to carry out analog computation. The analog computation includes carrying out an operation on operands. These operands are defined by electrical characteristics of sensor electrodes from different sensors in the set of sensors.
The sensors themselves can be of many types. Among the sensors are those that are configured such that the change in the electrical characteristic results from a change in temperature in sensed by the sensor electrode as a result of interaction with the measurement region, those that are configured such that the change in the electrical characteristic results from mechanical force experienced by the sensor electrode as a result of interaction with the measurement region, and those that are configured such that the change in the electrical characteristic results from interaction of the sensor electrode with a chemical species in the measurement region.
As used herein, a three-terminal sensor 10 has at least three terminals. However, it is not precluded from having more than three terminals.
Each of the first and second thread 12, 14 is a semiconducting channel. Examples of a semiconducting channel include those formed by a coating or deposition of a suitable substance on a thread that acts as a substrate. Examples of suitable substances include silicon, carbon nanotubes, graphene, MoS2, WeS2, a transition-metal oxides, and a chalcogenides. Other suitable substances are organic semiconductors, among which are P3HT, PEDOT:PSS, and Pentacene. The resultant semiconducting channel is either n-type, p-type, or ambipolar.
The first thread 12 has first and second sections 20, 22 that are integral with each other. The first section 20 forms a sensing electrode 24. As such, the sensing electrode 24 and the first section 20 share the same underlying substrate. This sensing electrode 20 is one that interacts with species in solution in such a way as to modulate an electrical characteristic thereof.
In the illustrated embodiment, the sensing electrode 24 occupies only a portion of the first thread 12. However, in some embodiments, the sensing electrode 24 is intertwined or completely merged with the first thread 12.
The sensing electrode 24 is typically formed by functionalizing the second section 22. As an example, the second section 22 can be functionalized by an antibody that binds to a particular protein. Once bound to the protein, the charge distribution in the complex formed by the combination of the protein and antibody will change relative to that of the antibody in its unbound state. This change in charge distribution manifests itself as a change in the electrical characteristics of the second section 22.
In general, the sensing electrode 24 is an electrode that is deposited on an underlying substrate, that interacts with the target analyte, and that, as a result of that interaction, manifests a disturbance in its electrical properties, including potential, current, charge, and/or impedance.
In some embodiments, the sensing electrode 24 is bare metal. In others, it is carbon. Still others feature a conductive polymer electrode that senses a biopotential. Examples of suitable biopotentials that such a sensing electrode 24 can sense include action potentials from neurons. As a result, such a sensing electrode 24 is particularly useful for electrocardiograms, electroencephalograms, electromyograms, and electrooculograms.
The change in electrical characteristic can be manifested in a variety of ways. For example, in some embodiments, an accumulation of charge occurs. In others, the impedance of the second section 22 changes. As used herein, “impedance” is a complex-valued quantity whose real part is a resistance and whose imaginary part, depending on its sign, is either a capacitance or an inductance.
The sensing electrode 24 can be tuned to sense physical quantities such as strain or temperature. Among these embodiments are those in which strain or temperature modulate resistivity of a material from which the sensing electrode 24 is made.
Other embodiments of a sensing electrode 24 are tuned to detect particular gases, liquids, or volatile chemicals. Other embodiments of a sensing electrode 24 are tuned to measure quantities of analytes. Examples of analytes that can be sensed by a suitably modified sensing electrode 24 include metabolites, cytokines, including interleukin-6, nucleic acids, including both deoxyribonucleic acids and ribonucleic acids, exosomes, and neuropeptides.
In many cases, the sensing function is achieved by functionalizing with antibodies, aptamers, or complementary deoxyribonucleic acids and ribonucleic acids that are prone to interact with a particular target analyte so as to change some electrical property, such as a transfer resistance, a capacitance, or a change in current.
In some embodiments, the sensing electrode 24 is coated with polyalanine for use as a pH sensor. In others, the sensing electrode 24 is coated with an ionophore matrix to provide the sensing electrode 24 with sensitivity to only a particular ion. Examples of such ionophore matrices include those based on sodium ion and those based on ammonium ion.
The second thread 14 includes a first section 26, a second section 28, and a coupling section 30 between the first and second sections 26, 28. The first and second section 26, 28 are coated with a material that permits them to be used as measurement terminals for sensing the change in the electrical characteristic of the sensing electrode 24.
The first and second threads 12, 14 thus combine to form a three-terminal device with one terminal on the first thread 12 and two terminals on the second thread 14. The sensing electrode 24 forms the terminal on the first thread and the first and second sections 26, 28 form the two terminals on the second thread 14.
In operation, the embodiment shown in
Meanwhile, a sensing electrode 24 that has been tuned to interact with a particular analyte is placed in a solution 32 having an unknown concentration of that analyte. Interaction between the analyte and the sensing electrode 24 perturbs the electrical properties of the sensing electrode 24.
In the embodiment shown in
The second section 28 communicates the perturbation to the coupling section 30. As a result, the perturbation is communicated to the first thread 12. This, in turn, disturbs the thread current that flows through the first thread 12. By monitoring this thread current, it is possible to make inferences concerning the extent to which the analyte is present in solution. Moreover, since the thread current's magnitude can be controlled by the voltage between the ends of the second thread, it is possible to amplify the effect of the perturbation, thus improving signal-to-noise ratio.
An alternative embodiment, shown in
A third embodiment, shown in
The third embodiment is analogous in structure to a field-effect transistor in which the measurement electrode 24 has been connected to a terminal other than the gate, i.e., top either the drain or source.
In this embodiment, a first voltage VG is applied to the third thread 34 and a second voltage VD, which is referenced to the same potential, is applied to the source terminal S associated with the second thread 14. This causes a current ID from source S to drain D that can be measured. The presence or absence of analytes thus causes a change in the electric field at the gate G, which serves to modulate the measured current ID.
The coupling region 16 in
The coupling region 16 in
The sensors 10 shown in
The coupling region 16 in
In some cases, it is useful to combine sensors 10 to form a sensor fabric 50 as shown in
The sensor fabric 50 of
A sensor fabric 50 as shown in
The first, second, and third sensors 10′, 10″, 10′″ have been described as measuring different analytes at the same general location. The result is a sensor fabric 50 that has species diversity. By having different kinds of sensor electrodes 24, it becomes possible to take measurements of many different species in the same general area and to pick out whichever measurement is of current interest at any instant by using the multiplexing architecture introduced by
However, other embodiments of the sensor fabric 50 achieve spatial diversity by having the measurement electrodes 24′, 24″, 24′″ be of the same type but positioned with their sensing portions at different locations.
But there is no reason they cannot instead all be measuring the same thing but at different locations. In such cases, the sensors 24′, 24″, 24′″ are implanted at different locations. This can be achieved by having the sensors sensor 24′, 24″, 24′″ integrated into threads of different lengths. To further enhance spatial resolution, the configuration shown in
A sensor fabric 50 that implements a sensor array with spatial diversity is particularly useful for analysis of brain activity. In such cases, multiple sensor electrodes 24′, 24″, 24′″ for sensing electrical activity in the brain can be disposed at various locations.
As the number of multiplexed sensors 10′, 10″, 10′″ in a fabric increases, a new problem emerges. The process of turning particular sensors off and leaving only one turned on requires control electronics. Increasing the number of sensors 10′, 10″, 10′″ thus increases the number of connections that must be made to implement sensor multiplexing.
To ameliorate this difficulty, it is useful to arrange the sensors 10′, 10″, 10′″ in a binary tree. This provides the ability to address an individual sensor 10′, 10″, 10′″ using significantly fewer connections. In general, the number of connections required to address a particular sensor 10′, 10″, 10′″ increases with the number of levels in the resulting binary tree rather than with the number of sensors 10′, 10″, 10′″. More precisely, the number of connections required to address a particular sensor 10′, 10″, 10′″ out of N such sensors falls from N connections to log2(N) connections.
For convenience, the actual switching process required to select a particular sensor 10′, 10″, 10′″ can be implemented using special logic sensors that sense a logic state. Such sensors have first and second threads 12, 14 as shown in
Since the logic sensors effectively simulate the operation of field-effect transistors, they can also inter-connected to each other to implement arbitrary Boolean logic expressions. This makes it possible to implement simple logic gates within the sensor fabric 50 itself.
It is also possible to interconnect sensors 10 to implement analog computers.
The first analog computer 64 comprises sensors 13 connected with their respective second threads 14 in series. This provides a way to measure the sum of the impedances of all the sensor elements 24 disposed along the resulting conducting path.
The second analog computer 66 comprises sensors 13 connected with their respective second threads 14 in parallel. By applying suitable control voltages to the respective first threads 12, it is possible to compute the parallel impedance of any combination of two or more sensor elements 24.
The third analog computer 68 features a combination of the first and second analog computers 64. 66.
The threads 12, 14, 34 referred to herein include anything that can be stitched, sewn, knitted, or patterned. Threads can be made of linen, cotton, silk, nylon, rubber, wool, metallic, polyurethane, polyester, rubber, polyimide or any other natural or synthetic polymer that has been suitably treated to acquire the appropriate semiconducting properties. The semiconductor can be one that is n-type, one that is p-type, or one that is ambipolar.
Also included within the scope of a “thread” are other flexible substrates such as polyimide, paper, polyethylene terephthalate, parylene, polydimethylsiloxane, and other substances that be screen-printed, ink-jet printed, gravure printed, or laser patterned.
Suitable methods for making such threads are described in WO2017/023727, published on Feb. 9, 2017, the contents of which are incorporated herein by reference.
The portions of the first and second threads 12, 14 that are intended for electrical connection to instrumentation or power sources are made of any metallic or conducting material, such as gold, silver, carbon, copper, zinc, aluminum, platinum, or palladium, with or without a substrate or conductive polymer, PEDOT, polyaniline, polypyrrole, polyphenylene sulfide, poly(acetylene)s, polyphenylene vinylene. The carbon can be any carbon allotropes, such as graphite or graphene, or can be in the form of a carbon nanotube.
Examples of dielectric 18 include ion gel, ionic liquid, deep eutectic solvent mixtures, gels of ionic liquids, deep eutectic solvent mixtures, oxides, silicon dioxide, hafnium oxide, polymers, and electrolytes.
In some embodiments, the three-terminal sensor 10 is uncoated. In others, the three-terminal sensor 10 is coated with a suitable protective dielectric or insulating layer to protect the three-terminal sensor 10 from humidity or fouling. Examples of suitable materials include parylene, polydimethylsiloxane, polystyrene, and oxides.
This application claims the benefit of the Aug. 12, 2019 priority date of U.S. Provisional Application 62/885,620, the contents of which are herein incorporated by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/US2020/045763 | 8/11/2020 | WO |
Number | Date | Country | |
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62885620 | Aug 2019 | US |