Wearable muscle atrophy sensors

Abstract

In some aspects, the techniques described herein relate to a system for monitoring muscle atrophy, the system including: a muscle atrophy sensor (100) including at least two stretchable conductors (105) incorporated into a stretchable substrate (110), the substrate configured as a sleeve or garment to be worn by a user such that the substrate wraps around a portion of the body of the user, the at least two stretchable conductors thereby forming inductive coils configured to stretch in conjunction with the substrate, wherein a first conductor and a second conductor of the at least two stretchable conductors are inductively coupled such that a time-varying current applied to the first conductor induces a voltage on the second conductor (402); and a controller (300) that is electrically coupled to the muscle atrophy sensor, the controller configured to measure the voltage on the second conductor (404) for calculating a circumference of the portion of the body of the user (406).

Description

WEARABLE MUSCLE ATROPHY SENSORSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to, and benefit of, U.S. Provisional Patent Application Serial No. 63 / 581,314, entitled “WEARABLE MUSCLE ATROPHY SENSORS”, and filed on September 8, 2023. The disclosure of which is hereby incorporated by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under 80NSSC21K1261 awarded by The National Aeronautics and Space Administration. The government has certain rights in the invention.BACKGROUND

[0003] Muscle atrophy is the loss of skeletal muscle mass resulting in muscle weakness and loss of strength and mobility that impacts patients suffering from various diseases, aging, muscle disuse, and more. Reductions in both strength and size of the muscles can result in a greater risk for injury and a reduced quality of life. Disease-induced muscle atrophy can occur from multiple different conditions including intensive-care-induced skeletal muscle weakness, cancer cachexia, chronic inflammatory disease-induced muscle weakness, and neurological disorders. Sarcopenia is the loss of muscle mass and strength that occurs with aging. Space travel also causes rapid and pronounced muscle atrophy in astronauts due to extended exposure to weightlessness. Muscle atrophy, however, is not limited to the adult population and can occur in children with critical illnesses or genetic disorders.

[0004] Magnetic resonance imaging (MRI) is considered the “gold standard” for assessing muscle size and volume; however, MRI is both time and resource intensive. For example, a 1.5 T MRI scanner itself may cost up to $1.5 million, not including the cost per scan or maintenance costs. Other non-invasive imaging techniques are also capable of accurately measuring muscle size such as ultrasonography (US) and computed tomography (CT). USimaging suffers from strong artifacts and CT involves radiation exposure to the patient. Both US and CT are costly and require the presence of a highly knowledgeable operator. MRI, CT, or US imaging techniques are generally used when a complete assessment of muscle properties, including size, mass, density, composition, and adipose tissue infiltration, is needed for diagnosis of muscle diseases. Dual energy X-ray absorptiometry (DXA) and bioelectric impedance analysis (BIA) provide estimations of body composition and muscle mass, but not muscle size or volume.SUMMARY

[0005] Disclosed herein is a wearable sensor for monitoring muscle atrophy. Anthropometric measurements (i.e., measuring limb circumference with a flexible tape measure) are the most widely used technique for initial estimation in changes of muscle size in the primary care setting. Anthropometry is the most easily accessible and inexpensive method for assessing the size and composition of the human body. Anthropometric measurements have been found to be in high level of agreement with MRI scans and are capable of providing a good index of muscle volume in adults. Thus, the disclosed sensor allows for quick and accurate monitoring of muscle atrophy similar to anthropometric methods. However, designing an electromagnetic sensor for wearable, accurate monitoring of muscle atrophy is challenging: the sensor not only needs to be tightly wrapped around the limb, but also needs to be able to stretch to adjust for changes in muscle size.

[0006] The disclosed wearable sensor for monitoring muscle atrophy is built on Faraday’s law of induction and exploits the dependence of magnetic flux density on cross- sectional area. The sensor generally includes wrap-around transmit and receive coils that stretch to fit changing limb sizes using a stretchable conductor (e.g., conductive threads, as discussed below). Changes in the cross-sectional area of the coil result in changes in both the magnitude and the phase of the transmission coefficient between coils. In some implementations, the stretchable conductor is liquid metal, which can be screen printed onto neoprene or embedded into polymer tubes to create stretchable coils. Conductive inks can be screen printed onto stretchable fabric or knitted fabric substrates. Conductive threads (e-threads) have often been targeted for conformal on-body applications, including stretchable MRI coils for joint imaging. E-threads, for example, demonstrate low losses at radiofrequencies (RF), have high mechanicalstrength, are washable, and can easily be embedded into fabrics. In some cases, stretchability is achieved using a predetermined zigzag stitch on the sewing machine; however, limited analysis or optimization of stretch or stitching methods is performed. A zigzag pattern has also been proposed for fluid transport in wearable applications via microfluidic channels but has not been explored with conductors or e-threads.

[0007] In this regard, disclosed herein is an electromagnetic sensor for monitoring muscle atrophy that addresses certain limitations described above. A wearable form factor is convenient, comprehensive, and multifunctional. The proposed device operates in a stand-alone manner without requiring any human intervention, whereas traditional anthropometric measurements require health technicians with comprehensive training to ensure accuracy. This empowers self-monitoring without the assistance of a second individual (e.g., medical professional) or additional instruction. In some cases, the disclosed sensor can cost less than a medical grade anthropometric tape measure due to the low cost of materials. The sensor can also be easily scaled to concurrently collect measurements across several limbs and across several locations on the same limb. A wearable device further allows for future, seamless incorporation with other sensors in a multipurpose system that could combine imaging, vital sign monitoring, and more.

[0008] Using the proposed sensor, individuals could easily monitor their muscle health on a daily, weekly, or monthly basis depending on their underlying condition. For instance, daily monitoring is warranted in crewmembers who may lose up to 10% muscle volume over the course of a 17-day spaceflight or critically ill patients in the intensive care unit (ICU) who may lose up to 10% of muscle volume during their first week of admission; however, other underlying conditions may require less frequent monitoring as the muscle atrophies at a slower rate. Periodic, individual monitoring in non-hospital environments will allow for more personalized implementation of treatment methods.

[0009] In some aspects, the techniques described herein relate to a sensor for monitoring muscle atrophy, the sensor including: a substrate formed of a stretchable material, the substrate configured as a sleeve or garment to be worn by a user such that the substrate wraps around a portion of the body of the user; a first stretchable conductor embedded in or positioned on the substrate at a first position to form a first inductive coil; and a second stretchable conductorembedded in or positioned on the substrate at a second position to form a second inductive coil, wherein the first and second inductive coils are configured to stretch in conjunction with the substrate, thereby varying a cross-sectional area of each of the first and second inductive coils, wherein the first and second inductive coils are inductively coupled such that a time-varying current applied to the first inductive coil induces a voltage on the second inductive coil, wherein the voltage on the second inductive coil is measured by a computing device to calculate a circumference of the portion of the body of the user.

[0010] In some aspects, the techniques described herein relate to a sensor, wherein the voltage on the second inductive coil is measured at a first time period and a second time period by the computing device to calculate a circumference of the portion of the body of the user at each of the first and second time periods, wherein a difference between the calculated circumference at the first and second time periods is indicative of muscle atrophy.

[0011] In some aspects, the techniques described herein relate to a sensor, wherein the second position is different from the first position such that the first and second inductive coils are spaced apart.

[0012] In some aspects, the techniques described herein relate to a sensor, wherein the first and second inductive coils are configured to operate in an inductive mode, such that the circumference of the first and second inductive coils is less than 0.1X.

[0013] In some aspects, the techniques described herein relate to a sensor, further including at least one additional stretchable conductor embedded in or positioned on the substrate to form at least one additional inductive coil for transmission or receipt of signals.

[0014] In some aspects, the techniques described herein relate to a sensor, wherein the first stretchable conductor and the second stretchable conductor each include a conductive thread arranged in a zigzag pattern.

[0015] In some aspects, the techniques described herein relate to a sensor, wherein the first stretchable conductor and the second stretchable conductor each include a conductive ink printed onto the substrate in a zigzag pattern.

[0016] In some aspects, the techniques described herein relate to a sensor, wherein the first stretchable conductor and the second stretchable conductor each include a flexible tubing having liquid metal disposed therein.

[0017] In some aspects, the techniques described herein relate to a sensor, wherein the liquid metal is gallium-indium eutectic (EGain).

[0018] In some aspects, the techniques described herein relate to a system for monitoring muscle atrophy, the system including: a muscle atrophy sensor including at least two stretchable conductors incorporated into a stretchable substrate, the substrate configured as a sleeve or garment to be worn by a user such that the substrate wraps around a portion of the body of the user, the at least two stretchable conductors thereby forming inductive coils configured to stretch in conjunction with the substrate, wherein a first conductor and a second conductor of the at least two stretchable conductors are inductively coupled such that a time-varying current applied to the first conductor induces a voltage on the second conductor; and a controller that is electrically coupled to the muscle atrophy sensor, the controller configured to measure the voltage on the second conductor for calculating a circumference of the portion of the body of the user.

[0019] In some aspects, the techniques described herein relate to a system, wherein the controller is further configured to: calculate the circumference of the portion of the body of the user from the measured voltage.

[0020] In some aspects, the techniques described herein relate to a system, wherein the controller is further configured to: transmit an indication of the measured voltage to a separate computing device, wherein the separate computing device is configured to calculate the circumference of the portion of the body of the user from the measured voltage.

[0021] In some aspects, the techniques described herein relate to a system, wherein the controller is configured to: measure the voltage on the second conductor at two or more different points in time; and calculate muscle atrophy in the user by: (i) calculating a circumference of the portion of the body of the user at each of the two or more different points in time, and (ii) calculating a difference between the calculated circumference at each of the two or more different points in time.

[0022] In some aspects, the techniques described herein relate to a system, wherein the first conductor and the second conductor are spaced apart on the stretchable substrate.

[0023] In some aspects, the techniques described herein relate to a system, wherein the first and second inductive coils are configured to operate in an inductive mode, such that the circumference of the first and second inductive coils is less than 0.1X.

[0024] In some aspects, the techniques described herein relate to a system, wherein the at least two stretchable conductors include three or more stretchable conductors incorporated into the stretchable substrate.

[0025] In some aspects, the techniques described herein relate to a system, wherein the at least two stretchable conductors each include a conductive thread arranged in a zigzag pattern.

[0026] In some aspects, the techniques described herein relate to a system, wherein the at least two stretchable conductors each include a conductive ink printed onto the substrate in a zigzag pattern.

[0027] In some aspects, the techniques described herein relate to a system, wherein the at least two stretchable conductors each include a flexible tubing having liquid metal disposed therein.

[0028] In some aspects, the techniques described herein relate to a system, wherein the liquid metal is gallium-indium eutectic (EGain).

[0029] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The foregoing summary, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the embodiments, there is shown in the drawings example constructions of the embodiments; however, the embodiments are not limited to the specific methods and instrumentalities disclosed. In the drawings:

[0031] FIG. 1 is an illustration of an exemplary muscle atrophy sensor;

[0032] FIG. 2 is an illustration of exemplary RLC circuits;

[0033] FIG. 3 is an illustration of an exemplary controller for controlling a muscle atrophy sensor;

[0034] FIG. 4 is an operational flow of an implementation of a method for monitoring muscle atrophy;

[0035] FIG. 5 is an illustration of example coils showing how the zigzag pattern allows the coils to stretch or contract;

[0036] FIG. 6 is an illustration of the unit cell used in the zigzag pattern; and

[0037] FIG. 7 is an illustration on example coil constructed using liquid metal.DETAILED DESCRIPTION

[0038] Referring to FIG. 1, a muscle atrophy sensor 100 is disclosed. The sensor 100 includes two wrap-around coils 105 including a transmitting (TX) coil 105A and a receiving (RX) coil 105B contained in a flexible substrate 110. The coils 105 are wrapped around a region of interest and are purposely placed on the same side of a joint to eliminate any fabric drift from joint flexion or extension. As can be seen in the example of FIG. 1, the flexible substrate 110 is placed around the calf of a user such that the coils 105 are on the same sides of both the knee and angle of the user.

[0039] The coils 105 are designed to operate in an inductive mode, such that the circumference of each coil 105 is less than 0.12. The inductive mode may be selected to exploit the dependence of magnetic flux density on cross-sectional area. In some embodiments, the coils 105 may be constructed out of a material such as e-thread. In other embodiments, liquid metal may be used for the coils 105. A suitable liquid metal may include an alloy such as Galliumindium eutectic (“EGain “). Other metals or metal alloys may be used.

[0040] Each coil 105 can be described as resonant RLC circuits 205 with magnetic coupling illustrated as a mutual inductance, Lm, in FIG. 2. A transmitter circuit 205A represents the TX coil 105 A and a receiver circuit 205B represents the RX coil 105B. In summary, the circuits 205 operate in the inductive frequency regime (e.g., where the circumference is less than0. IX) where the circuit 205A is the transmitter, and the circuit 205B is the receiver. In this frequency range, the dependence of magnetic flux density on cross-sectional area can be exploited to monitor changes in muscle size. It is important to note that the sensor 100 will have similar performance on realistic anatomy and irregular shapes due to this underlying operational principle. That is, sensor 100 performance depends on overall cross-sectional area, regardless of the coil 105 shape.

[0041] To improve transmission performance, the inductive coils 105 are made resonant with a lumped component. The RX coil 105B receives the signal transmitted by the TX coil 105A, quantified by a transmission coefficient (S21) between the coils 105. In some implementations, the coils 105, in the flexible substrate 110, can dynamically stretch with corresponding changes in limb circumference due to a unique zigzag stitching technique with conductive e-threads on stretchable spandex fabric of the substrate 110.

[0042] Such an implementation is shown in FIG. 5. In particular, FIG. 5 shows how a coil 105 constructed from e-thread in a zigzag pattern can stretch or contract to allow for the coil 105 to be placed over muscles having a wide range of circumferences. 501 shows the unstretched zigzag coil 105 at 28 cm. 503 shows the zigzag coil at 32 cm. 505 shows the zigzag coil at 36 cm. 507 shows the zigzag coil 105 fully stretched to 40 cm. In some such implementations (e.g., when the coils 105 are formed of a conductive thread or e-thread), the electrical length of the coils will remain the same for all circumferences due to the stitching mechani

[0043] In the inductive mode, the time-varying current from the TX coil 105 A will induce a time-varying magnetic flux density on the RX coil. This induces a voltage on the RX coil 105B based on Faraday’s law of induction:where VRX is the induced voltage on the RX coil, (pBis the magnetic flux, and N is the number of loops in the coil. The magnetic flux, < >B, is proportional to the number of field lines passing through that surface, where A is the surface area vector and B is the magnitude of the magnetic field:<PB = B • A

[0044] As the cross-sectional area of the coils 105 decreases, the voltage induced on the RX coil 105B will decrease. The magnitude of the transmission coefficient (|S2i|) will also decrease with the lower voltage. Thus, as the limb size decreases due to muscle atrophy, IS211 will decrease too.

[0045] The phase of the inductive coils 105 ( S21) is dependent on the reactance of the coil 105. The coil 105 is designed to be resonant by setting the reactance equal to zero; however, the reactance varies with coil 105 circumference. Thus, the coil 105 is only resonant at a singular limb circumference, and as the limb, and the corresponding coil 105, changes in size, the reactance will change as well. This response can be evaluated via the linear change in the ZS21 due to change in coil 105 (and limb) size. That is, there are two metrics that can be used to monitor limb size: a) magnitude of S21 and b) phase of S21. These two independent parameters can be leveraged to accurately monitor muscle atrophy using inductive coils.

[0046] In some implementations, as shown in FIG. 5, each inductive coil 105 is designed to stretch dynamically with limb size by employing a zigzag pattern. For example, for the maximum limb circumference (e.g., 40 cm at 501), the zigzag is fully stretched and is essentially a straight line. For the minimum limb circumference (e g., 28 cm at 501), the zigzag consists of taller and skinnier triangles. In some embodiments, the zigzag pattern of the coil 105 consists of units cells 601 that are triangles with an electrical length of 1 cm, and a height and width that is dependent on the variable limb circumference that is being measured.

[0047] An example unit cell 601 is illustrated in FIG. 6. As shown in FIG. 6, the two sides of the unit cell 601 are arbitrarily set to 0.5 cm. The width of the unit cell 601 is defined by the ratio of the current limb circumference to the maximum limb circumference. The height and angles of the unit cell 601 can be found using the Pythagorean theorem. The ratio and height of the unit cell 601 for a variety of limb circumferences are displayed in Table I:Table I

[0048] In some implementations, each inductive coil 105 includes a flexible / stretchable tubing (e.g., silicone tubing) that contains liquid metal. In some such implementations, the liquid metal is EGain; however, the present disclosure is not intended to be limiting in this regard.FIG. 7 is an illustration on example coil 105 constructed using liquid metal. As shown, the coil 105 consists of a silicon tube fdled with liquid metal. In the example shown, silicone is used for the tubing because of its stretching capabilities, biocompatibility, and commercial availability. Other materials may be used. The diameter of the tube may be between 0.3 to 1.0 mm, for example.

[0049] While generally shown in the figures as including just two inductive coils 105, it will also be appreciated that the disclosed muscle atrophy sensor 100 may include any number of inductive coils 105. For example, the sensor 100 may include three coils 105 - one TX coil 105A and two RX coils 105B or two TX coils 105A and one RX coil 105B. In another example, the sensor 100 may include four coils 105 - two TX coils 105 A and two RX coils 105B, or any combination thereof. In yet another example, the sensor 100 may include six coils 105 - three pairs of TX / RX coils 105, or any combination thereof. Thus, it should be appreciated that the present disclosure is not intended to be limiting in this regard.Muscle Atrophy Monitoring

[0050] FIG 3. is a diagram of an example controller 300 for obtaining measurements from the aforementioned muscle atrophy sensor 100 and / or for monitoring muscle atrophy. Generally, controller 300 is implemented in a portable package that can be incorporated into a garment (e.g., the flexible substrate 110) with the muscle atrophy sensor 100 described above and / or that can be separately carried by a user. Alternatively, the muscle atrophy sensor 100 can be temporarily connected to controller 300 for recording measurements and monitoring muscle atrophy as described below. Controller 300 may be able to connect to one or more of thedisclosed muscle atrophy sensors 100 to monitor muscle atrophy at multiple locations on a user. For example, multiple of the disclosed muscle atrophy sensors could be incorporated into a single garment (e.g., a pair of pants) such that controller 300 is connected to each of the multiple sensors 100 for monitoring muscle atrophy at different locations.

[0051] Controller 300 is shown to include a processing circuit 302 that includes a processor 304 and a memory 310. Processor 304 can be a general-purpose processor, an application specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a group of processing components (e.g., a central processing unit (CPU)), or other suitable electronic processing structures. In some implementations, processor 304 is configured to execute program code stored on memory 310 to cause controller 300 to perform one or more operations, as described below in greater detail.

[0052] Memory 310 can include one or more devices (e.g., memory units, memory devices, storage devices, etc.) for storing data and / or computer code for completing and / or facilitating the various processes described in the present disclosure. In some implementations, memory 310 includes tangible (e g., non-transitory), computer-readable media that stores code or instructions executable by processor 304. Tangible, computer-readable media refers to any physical media that is capable of providing data that causes controller 300 to operate in a particular fashion. Example tangible, computer-readable media may include, but is not limited to, volatile media, non-volatile media, removable media and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data.

[0053] Accordingly, memory 310 can include random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), electronically erasable programmable read-only memory (EEPROM), hard drive storage, temporary storage, nonvolatile memory, flash memory, optical memory, or any other suitable memory for storing software objects and / or computer instructions. Memory 310 can include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present disclosure. Memory 310 can be communicably connected to processor 304, such as via processing circuit302, and can include computer code for executing (e.g., by processor 304) one or more processes described herein.

[0054] While shown as individual components, it will be appreciated that processor 304 and / or memory 310 can be implemented using a variety of different types and quantities of processors and memory. For example, processor 304 may represent a single processing device or multiple processing devices. Similarly, memory 310 may represent a single memory device or multiple memory devices. Additionally, in some implementations, controller 300 may be implemented within a single computing device (e.g., one server, one housing, etc.). In other implementations, controller 300 may be distributed across multiple servers or computers (e.g., that can exist in distributed locations). For example, controller 300 may include multiple distributed computing devices (e.g., multiple processors and / or memory devices) in communication with each other that collaborate to perform operations. For example, but not by way of limitation, an application may be partitioned in such a way as to permit concurrent and / or parallel processing of the instructions of the application. Alternatively, the data processed by the application may be partitioned in such a way as to permit concurrent and / or parallel processing of different portions of a data set by the two or more computers.

[0055] It should be appreciated that, in certain implementations, controller 300 can be part of another computing device and / or the components of controller 300 can be shared with, or the same as, a host device. For example, if controller 300 is implemented via a laptop computer, then controller 300 may utilize the processing circuit, processor(s), and / or memory of the laptop computer to perform the functions described herein. It should also be appreciated that, in some implementations, controller 300 may include less than all of the components shown in FIG. 3 and / or certain components of FIG. 3 may be hosted on another device.

[0056] Memory 310 is shown to include a muscle atrophy calculator 312 that monitors muscle atrophy in a user using the sensor 100 described herein. In particular, muscle atrophy calculator 312 can be configured to obtain voltage measurements from the RX coil 105B of the sensor 100 and can use the obtained voltage measurements to calculate a circumference of a body part of the user (i.e„ the body part surrounded by the RX coil 105B of the sensor 110. In some implementations, muscle atrophy calculator 312 obtains measurements from the RX coil 105B of the sensor 100 at different points in time, such as periodically (e.g., every few hours,every day, every week, etc.) and can optionally store measurements or the circumference(s) calculated from the measurements, to monitor muscle atrophy over time. In other words, muscle atrophy calculator 312 may calculate muscle atrophy based on the difference in the circumference of a body part over time.

[0057] In this regard, controller 300 can include a radiofrequency (RF) generator 320 and / or an input-output (I / O) interface 322 for operating the above-discussed muscle atrophy sensor 100. RF generator 320, in particular, may be configured to generate and / or apply a timevarying current (e.g., an RF signal) on the TX coil 105 A of the sensor 100. In some implementations, the applied RF signal is less than 75 MHz; however, the present disclosure is not intended to be limiting in this regard. Rather, the frequency of the RF signal may be selected based on an initial circumference of the portion of the body to be measured to ensure that the coils 105 of the sensor 100 operating in the inductive mode. In some such implementations, the applied RF signal ranges from 30 to 75 MHz. VO interface 322 can include any number of interfaces for electrically connecting controller 300 to the sensor 100. For example, I / O interface 322 can include an output interface for delivering energy to the TX coil 105 A of the sensor 100 (e.g., from RF generator 320). VO interface 322 may also include an input for obtaining a voltage signal from the RX coil 105B of the sensor 100.

[0058] Controller 300 is also shown to include a communications interface 324 that facilitates communications between controller 300 and any external components or devices. For example, communications interface 324 can provide means for transmitting data to, or receiving data from, a separate / remote computing device (e.g., a desktop or laptop computer). Accordingly, communications interface 324 can be or can include a wired or wireless communications interface (e.g., jacks, antennas, transmitters, receivers, transceivers, wire terminals, etc.) for conducting data communications, or a combination of wired and wireless communication interfaces. In some implementations, communications via communications interface 324 are direct (e.g., local wired or wireless communications) or via a network (e.g., a WAN, the Internet, a cellular network, etc.). For example, communications interface 324 can include a Wi-Fi transceiver for communicating via a wireless communications network and / or a short-range wireless transceiver (e.g., a Bluetooth transceiver) for short-range, direct wireless communications. In another example, communications interface 324 may include cellular or mobile phone communications transceivers. In yet another example, communications interface324 can include a USB port or other interface for transmitting data to an external device via a wired connection.

[0059] In some implementations, controller 300 is configured as a stand-alone device that can operate the muscle atrophy sensor 100 described herein on its own. In other words, controller 300 may be designed to generate and apply a signal via the TX coil 105 A of the sensor 100, measure a voltage on the RX coil 105B of the sensor 100, calculate a circumference of the corresponding body part of the user, and / or monitor muscle atrophy over time. Thus, in some such implementations, controller 300 can include additional components that are not illustrated (e g., a battery) to facilitate such operations. However, it should be appreciated that certain components or functionality of controller 300 may be hosted by a separate computing device, e.g., to reduce computational overhead and / or power requirements of controller 300. For example, in some implementations, controller 300 can be configured to simply apply an RF signal on the TX coil 105 A of the sensor 100 and / or record a voltage on the RX coil 105B of the sensor 100 and can then transmit an indication of the recorded voltage to a remote device for processing (e.g., to calculate circumference and / or monitor muscle atrophy).

[0060] FIG 4. is a flow chart illustrating an exemplary method 400 for monitoring muscle atrophy in a subject (i.e., a user or patient). In some implementations, process 400 is implemented by controller 300 as described above. However, process 400 may be at least partially implemented by another computing device. For example, as mentioned above, in some implementations, controller 300 may transmit data (e.g., measure voltages) to a remote device for processing. It will be appreciated that certain steps of the method 400 may be optional and, in some implementations, the method 400 may be implemented using less than all of the steps. It will also be appreciated that the order of steps shown in FIG. 4 is not intended to be limiting.

[0061] At step 402, a time-varying current (e.g., an RF signal) is applied to the TX coil 105 A of the muscle atrophy sensor 100 described herein. The RF signal may be applied by the controller 300 via the RF generator 320.

[0062] In conjunction, at step 404, a voltage on the RX coil 105B of the muscle atrophy sensor 100 is measured. The voltage on the RX coil 105B may be measured by the controller 300 via the I / O interface 322. As mentioned above, in the inductive mode, the time-varying current from the TX coil 105 A will induce a time-varying magnetic flux density on the RX coil105B. This induces a voltage on the RX coil 105B based on Faraday’s law of induction. As the cross-sectional area of the coils 105 decreases, the voltage induced on the RX coil 105B will also decrease. The magnitude of the transmission coefficient (| S211) will also decrease with the lower voltage. Thus, as the limb size decreases due to muscle atrophy, | S211 will decrease too.

[0063] At step 406, the circumference of a body part of the user is calculated from the measured voltage on the RX coil. The circumference of the body part may be calculated by the muscle atrophy calculator 312. To this point, as discussed above, the disclosed muscle atrophy sensor 100 can be formed into a wearable sleeve or other garment for measuring the circumference of a body part of the user, e.g., a leg, an arm, etc. From the measured voltage on the RX coil 105B, limb size (e.g., in circumference) can be calculated based on a magnitude of S21 and a phase of S21. As shown, steps 404 and 406 of the method 400 can be repeated in a loop (e.g., iteratively, periodically) at two or more points in time to calculate the circumference of the body part over time. Then, at step 408, muscle atrophy can be monitored based on the calculated circumference of a body part over time. For example, the circumference of the user’s leg at a first time period can be subtracted from the circumference of the user’s leg at a second, earlier time period to determine a reduction in leg circumference between the two time periods, indicative of muscle atrophy.Configuration of Certain Implementations

[0064] The construction and arrangement of the systems and methods as shown in the various implementations are illustrative only. Although only a few implementations have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative implementations. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the implementations without departing from the scope of the present disclosure.

[0065] The present disclosure contemplates methods, systems, and program products on any machine-readable media for accomplishing various operations. The implementations of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Implementations within the scope of the present disclosure include program products including machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures, and which can be accessed by a general purpose or special purpose computer or other machine with a processor.

[0066] When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general-purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

[0067] Although the figures show a specific order of method steps, the order of the steps may differ from what is depicted. Also, two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.

[0068] It is to be understood that the methods and systems are not limited to specific synthetic methods, specific components, or to particular compositions. It is also to beunderstood that the terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting.

[0069] As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another implementation includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another implementation. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0070] “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0071] Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises,” means “including but not limited to,” and is not intended to exclude, for example, other additives, components, integers or steps. “Exemplary” means “an example of’ and is not intended to convey an indication of a preferred or ideal implementation. “Such as” is not used in a restrictive sense, but for explanatory purposes.

[0072] Disclosed are components that can be used to perform the disclosed methods and systems. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed that while specific reference of each various individual and collective combinations and permutation of these may not be explicitly disclosed, each is specifically contemplated and described herein, for all methods and systems. This applies to all aspects of this application including, but not limited to, steps in disclosed methods. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific implementation or combination of implementations of the disclosed methods.

Claims

WHAT IS CLAIMED IS:

1. A sensor for monitoring muscle atrophy, the sensor comprising: a substrate formed of a stretchable material, the substrate configured as a sleeve or garment to be worn by a user such that the substrate wraps around a portion of the body of the user; a first stretchable conductor embedded in or positioned on the substrate at a first position to form a first inductive coil; and a second stretchable conductor embedded in or positioned on the substrate at a second position to form a second inductive coil, wherein the first and second inductive coils are configured to stretch in conjunction with the substrate, thereby varying a cross-sectional area of each of the first and second inductive coils, wherein the first and second inductive coils are inductively coupled such that a time-varying current applied to the first inductive coil induces a voltage on the second inductive coil, wherein the voltage on the second inductive coil is measured by a computing device to calculate a circumference of the portion of the body of the user.

2. The sensor of claim 1 , wherein the voltage on the second inductive coil is measured at a first time period and a second time period by the computing device to calculate a circumference of the portion of the body of the user at each of the first and second time periods, wherein a difference between the calculated circumference at the first and second time periods is indicative of muscle atrophy.

3. The sensor of claim 1, wherein the second position is different from the first position such that the first and second inductive coils are spaced apart.

4. The sensor of claim 1, wherein the first and second inductive coils are configured to operate in an inductive mode, such that the circumference of the first and second inductive coils is less than 0.1 A,.

5. The sensor of claim 1, further comprising at least one additional stretchable conductor embedded in or positioned on the substrate to form at least one additional inductive coil for transmission or receipt of signals.

6. The sensor of claim 1, wherein the first stretchable conductor and the second stretchable conductor each comprise a conductive thread arranged in a zigzag pattern.

7. The sensor of claim 1, wherein the first stretchable conductor and the second stretchable conductor each comprise a conductive ink printed onto the substrate in a zigzag pattern.

8. The sensor of claim 1, wherein the first stretchable conductor and the second stretchable conductor each comprise a flexible tubing having liquid metal disposed therein.

9. The sensor of claim 8, wherein the liquid metal is gallium-indium eutectic (EGain).

10. A system for monitoring muscle atrophy, the system comprising: a muscle atrophy sensor comprising at least two stretchable conductors incorporated into a stretchable substrate, the substrate configured as a sleeve or garment to be worn by a user such that the substrate wraps around a portion of the body of the user, the at least two stretchable conductors thereby forming inductive coils configured to stretch in conjunction with the substrate, wherein a first conductor and a second conductor of the at least two stretchable conductors are inductively coupled such that a time-varying current applied to the first conductor induces a voltage on the second conductor; and a controller that is electrically coupled to the muscle atrophy sensor, the controller configured to measure the voltage on the second conductor for calculating a circumference of the portion of the body of the user.

11. The system of claim 10, wherein the controller is further configured to: calculate the circumference of the portion of the body of the user from the measured voltage.

12. The system of claim 10, wherein the controller is further configured to: transmit an indication of the measured voltage to a separate computing device, wherein the separate computing device is configured to calculate the circumference of the portion of the body of the user from the measured voltage.

13. The system of claim 10, wherein the controller is configured to: measure the voltage on the second conductor at two or more different points in time; andcalculate muscle atrophy in the user by: (i) calculating a circumference of the portion of the body of the user at each of the two or more different points in time, and (ii) calculating a difference between the calculated circumference at each of the two or more different points in time.

14. The system of claim 10, wherein the first conductor and the second conductor are spaced apart on the stretchable substrate.

15. The system of claim 10, wherein the first and second inductive coils are configured to operate in an inductive mode, such that the circumference of the first and second inductive coils is less than 0.

116. The system of claim 10, wherein the at least two stretchable conductors comprise three or more stretchable conductors incorporated into the stretchable substrate.

17. The system of claim 10, wherein the at least two stretchable conductors each comprise a conductive thread arranged in a zigzag pattern.

18. The system of claim 10, wherein the at least two stretchable conductors each comprise a conductive ink printed onto the substrate in a zigzag pattern.

19. The system of claim 10, wherein the at least two stretchable conductors each comprise a flexible tubing having liquid metal disposed therein.

20. The system of claim 19, wherein the liquid metal is gallium-indium eutectic (EGain).

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