Wearable device for producing high frequency electrostimulation

Abstract

A limb wearable neurostimulation device for treating Restless Leg Syndrome (RLS) or Periodic Limb Movement Disorder (PLMD) comprises an electrostimulation electronics unit with a printed circuit board (PCB) including a neurostimulation electrical waveform generator. The generator produces atonic motor activation (TOMAC) excitation waveform for delivery by electrodes to patient skin, configured with constant current, frequency of 1,000-5,000 Hz, zero-to-peak current amplitude of 10-50 mA. The device includes an electronics housing and a heat sink or insulating cover arranged to receive thermal conduction from PCB components and regulate thermal output of the electronics housing.

Description

WEARABLE DEVICE FOR PRODUCING HIGH FREQUENCY ELECTROSTIMULATIONPRIORITY

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application Serial No. 63 / 686.761, filed August 24. 2024, which is incorporated by reference herein in its entirety.BACKGROUND

[0002] Electrical nerve stimulation can be used to treat one or more conditions, such as chronic or acute pain, epilepsy, depression, bladder disorders, or inflammatory disorders. Certain neurological disorders can be attributed to overactivity of sensory or other peripheral nerve fibers which can disrupt quality of life, or the processing of such neural activity in the brain. Restless Legs Syndrome (RLS) and Periodic Limb / Leg Movement Disorder (PLMD) are two such neurological conditions that can significantly affect sleep in human subjects. RLS (which can also be called Willis-Ekbom Disease (WED)) subjects can experience uncomfortable tingling sensations in their lower limbs (legs) and, less frequently in the upper limbs (arms). RLS is characterized by an uncontrollable urge to move the affected limb(s). Such sensations can often be temporarily relieved by moving the limb voluntarily but doing so can interfere with the RLS subject's ability to fall asleep. PLMD subjects can experience spontaneous movements of the lower legs during periods of sleep, which can cause the PLMD subject to wake up. RLS can be a debilitating sleep disorder and can be comorbid with other sleep disorders such as insomnia or sleep apnea syndrome (SAS).BRIEF DESCRIPTION OF THE DRAWINGS

[0003] In the drawings, which are not necessarily drawn to scale, like numerals can describe similar components in different views. Like numerals having different letter suffixes can represent different instances of similarcomponents. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0004] FIG. 1 depicts an example of a limb wearable neurostimulation device for treating at least one of RLS or PLMD.

[0005] FIG. 2A depicts an electrostimulation electronics unit for use as part of a neurostimulation device.

[0006] FIG. 2B depicts insertion of an electrostimulation electronics unit into an opening of a removable strap.

[0007] FIG. 2C depicts an example of a limb wearable neurostimulation device for treating at least one of RLS or PLMD.

[0008] FIG. 2D is an exploded view of an example of a limb wearable neurostimulation device for treating at least one of RLS or PLMD.

[0009] FIG. 3A depicts a connection side of flexible printed circuit board of an example of an electrostimulation electronics unit.

[0010] FIG. 3B is a top view showing a mating of a connection side of a flexible printed circuit with a main printed circuit board of an example of an electrostimulation electronics unit.

[0011] FIG. 3C is a perspective view showing a mating of a connection side of a flexible printed circuit with a main printed circuit board of an example of an electrostimulation electronics unit.

[0012] FIG. 4A depicts an example of housing a circuitry unit and a battery in an example of an electrostimulation electronics unit.

[0013] FIG. 4B depicts a thermally conductive foil enclosing a circuitry unit and a battery in an example of an electrostimulation electronics unit.

[0014] FIG. 5 is a flowchart showing a process for treating at least one of RLS or PLMD via a limb wearable neurostimulation device.

[0015] FIG. 6 illustrates generally an example of a block diagram of a machine.DETAILED DESCRIPTION

[0016] Approaches to treating Restless Leg Syndrome (RLS) and Periodic Limb Movement Disorder (PLMD) can include pharmacological interventionsand non-pharmacological interventions such as lifestyle changes. Such approaches can involve challenges of efficacy, side effects, tolerance to therapy, or challenges associated with patient non-compliance. Neurostimulation devices can be useful in certain medical applications to treat neurological and physiological conditions. Such devices typically employ electrical stimulation to modulate neural activity in specific regions of the body. Thus, neurostimulation can provide a treatment modality for certain limb-related disorders, such as Restless Leg Syndrome (RLS) and Periodic Limb Movement Disorder (PLMD), such as for alternative or additional treatment to pharmacological agents, lifestyle changes, massage therapy, compression therapy, etc.

[0017] One approach for neurostimulation involves an implantable neurostimulation device. Such devices are surgically implanted within the body to deliver electrical stimulation directly to a specified neural target. Implantable systems are generally designed for long-term, continuous operation within the body. Typically, an implantable neurostimulation system consists of several components: an implantable pulse generator (IPG), stimulation leads, and electrodes. The IPG, which houses the battery and stimulation circuitry, is usually implanted subcutaneously in an accessible area of the body. The stimulation leads, containing multiple electrodes, are surgically positioned near the target neural structures. Implantable devices face unique challenges in terms of biocompatibility, longevity, and power management. The materials used must be carefully selected to minimize tissue reaction and ensure long-term stability' within the body. Power consumption is also an important consideration, as in certain devices battery replacement can involve surgical intervention. Implantable neurostimulation devices generally operate at lower frequencies and amplitudes compared to external stimulators (e.g., to preserve power), as they can deliver current directly to neural structures without the impedance of skin and subcutaneous tissues. Implantable neurostimulation has been applied in various neurological and chronic pain conditions, including spinal cord stimulation for chronic pain, deep brain stimulation for Parkinson's disease and essential tremor, and sacral nerve stimulation for bladder control disorders. While implantableneurostimulation devices offer the advantage of targeted, continuous therapy without the need for external hardware, they also come with risks associated with surgical implantation, potential device complications, and longevity considerations.

[0018] Another approach to neurostimulation involves Transcutaneous Electrical Nerve Stimulation (TENS). TENS devices typically generate low- voltage electrical currents that stimulate nerves in the area of pain via delivery of the current to an external body location such as patient skin. TENS devices involve electrical pulses delivered via a capacitive discharge, such as at relatively frequencies ranging from 1 Hertz (Hz) to 250 Hz and maximum current amplitudes below 50 mA. TENS is often delivered at considerably low duty cycles, e.g., 5-10%, between long relaxation periods. Such low duty cycles can involve relatively low root means squared (RMS) current actually delivered to the patient, e.g. 1-3 mA. and therefore, relatively low charge delivery'. As such, the devices can deliver relatively low energy, but generally remain insufficient to generate action potentials above, e.g., neural firing thresholds. Without being bound by theory, TENS applications can provide clinical benefit for chronic and acute pain management through gate control theory' which suggests that peripheral nerves carrying pain sensations can be overstimulated by the low-voltage currents delivered by TENS, which can, in turn, reduce the patient's perception of pain signals. Thus, while the electrical current delivered by TENS delivers insufficient energy for a therapeutic stimulation motor nerves (e.g., activating proprioceptive afferents). it can serve as a kind of counter-irritant that masks pain signals. Additionally, higher frequency TENS, e.g., about 100 Hz, is thought to stimulate the production of P-endorphins, brain chemicals that modulate pain signals. TENS has been FDA approved for general pain relief for conditions such as osteoarthritis, bursitis, tendonitis, and back pain. TENS devices have a lower risk profile than implantable devices, as they do not require surgical intervention and can be easily removed if necessary7. However, they are limited in their reach and efficacy compared to implantable neurostimulation.

[0019] Yet another approach to neurostimulation involves high frequency stimulation (HFS), which involves the use of frequencies greater than 5kilohertz (KHz), which is above the typically perceived pain threshold and generates little or no paresthesia. Unlike TENS, where the frequency is usually constant and the duty cycle is modulated (e.g., 5-10%), HFS employs a modulated duty cycle or burst mode at a much higher current amplitude to directly stimulate peripheral nerves. However, HFS typically is able to avoid the "sizzle and burn" effects encountered in many TENS applications. Specifically, due to the higher frequency, the charge density can be reduced while delivering the same charge or energy, as compared to TENS, thus the heat dissipated at the electrode interface is reduced. Producing HFS in a wearable, battery-powered device presents a considerable challenge in terms of power management, heat dissipation, and overall device efficiency. The present inventors have conceived of technique for HFS neurostimulation in a limb wearable neurostimulation device to treat at least one of RLS or PLMD, including waveform generation, thermal regulation, and firmware control of an electrostimulation output to overcome the above-identified challenges. The devices and methods discussed herein can facilitate safe, comfortable delivery of a waveform that induces tonic motor activation (TOMAC) of a patient muscle, without inducing uncomfortable paresthesia, waking a patient from sleep, or significantly heating (e.g., maintaining less than 10° greater than patient skin temperature) patient skin. As described below, achieving such a therapeutic waveform can involve a synergistic balance of several electrostimulation and thermal regulation parameters, several parameters of which are interdependent parameters or mutually dependent variables. Thus, devices and methods described herein involve optimizations which balance certain '‘trade-offs” of inherent factors in neurostimulation to arrive at an effective, safe, and portable (e.g., for use in at-home therapy) treatment for RLS or PLMD.

[0020] This document describes a limb wearable neurostimulation device to provide therapeutic relief to at least one symptom of RLS or PLMD. The device can facilitate transcutaneous (e.g., at an outermost layer of patient skin) delivery’ of a tonic motor activation (TOMAC) excitation waveform to elicit desired neurostimulation at a target body location of the affected limb. For example, the target body location can be a location associated with a peronealnerve, a sural nerve, a tibial nerve, a femoral nerve, or a branch thereof, or another location on patient skin associated with muscle activation. In an example, the device can include an electrostimulation electronics unit housing a printed circuit board (PCB) containing a neurostimulation electrical waveform generator. The waveform generator can produce a TOMAC excitation waveform with specified parameters to induce tonic muscle activation, including activation of proprioceptive afferents in a muscle of the patient. For example, the waveform can be generated, ultimately for transcutaneous delivery via electrodes at a constant current, with a frequency ranging from 500 hertz (Hz) to about 10,000 Hz (e.g., within a range of about 1,000 Hz to about 5,000 Hz), and a zero-to-peak current amplitude between 10 and 50 milliamperes (mA). In an example, the waveform can operate at a duty' cycle greater than about 25% (e.g., greater than about 20%, greater than about 30%, greater than about 40%, greater than about 50%, greater than about 75%, greater than about 90%. etc.) to facilitate sustained therapeutic efficacy over a specified duration (e.g., greater than 10 minutes, 20 minutes, 25 minutes, 30 minutes, or 40 minutes, such as a specified duration of about 30 minutes).

[0021] In an example, the TOMAC excitation waveform can be generated as a variable duty-cycle pulse-width modulated (PWM) waveform, allowing for dynamic adjustments based on the temperature feedback. For example, the electrostimulation electronics unit can include waveform modulation circuitry configured to adjust the duty cycle such that a device temperature remains within a safe range, not exceeding body temperature by more than 6 degrees Celsius. Such a feature can help avoid an instance where a device need be shut down and therapy entirely ceased to mitigate an overheating event of the wearable neurostimulation device.

[0022] In an example, the waveform generator can produce the TOMAC excitation waveform such that delivery of the waveform via the electrodes delivers a specified amount of charge to the patient's skin. For example, the waveform generator can produce a waveform for delivery within a range of about 0.1 to about 5 micro-coulombs per phase (pC / phase), and alternatively or additionally within a range about 0.001 to about 0.04 Coulombs per second(C / s). For example, the waveform can be delivered maintain its TOMAC efficacy despite an inherent reactive power loss related to the capacitive load (e.g., a natural capacitance of human skin), which can be at least 5 nanofarads (nF) (e.g., within a range of about 5 nF and about 150 nF, such as about 100 nF, depending on a frequency of the waveform delivered to the patient skin).

[0023] In an example, such as to facilitate desired stimulation (e.g., to achieve a desired amount of energy delivered to patient skin over time), the electrostimulation electronics unit can produce and deliver (e.g., via the waveform generator and associated circuitry) the TOMAC excitation waveform with a slew rate of less than about 25 microseconds (ps) rise-time and, alternatively or additionally, less than about 25 ps fall-time.

[0024] In an example, the electrostimulation electronics unit can include a thermal management system. The thermal management system can be configured to mitigate inherent challenges of delivering a waveform that is therapeutically effective via non-implantable (e.g., external) electrodes. For example, the electrostimulation electronics unit can include or use a heat sink or insulating cover arranged such as to receive thermal conduction from components (e.g., transistors, switches, etc. ) of the PCB. In an example, to promote a desired heat dissipation, the PCB layout can be arranged including certain thermally radiating components (e.g., substantially all transformers and switching power transistors), arranged toward a periphery of the PCB. Here, the heat sink or insulating cover can include a dispersion structure with thermal conduction contacts to these components, such as to spread and dissipate heat effectively. The dispersion structure can be, e.g., integrated into a flex circuit that also includes the interconnect for the electrodes. In an example, the thermal management system can facilitate transfer of thermal energy (e.g., via the heat sink) from the PCB at a rate greater than 0.2 Joules per second (J / sec), ensuring efficient heat dissipation during operation and even dispersion of the heat across the patient skin to avoid uncomfortable point source heating of the device.

[0025] The device as a whole can be a wearable solution, such as featuring an elongate strap that can substantially encircle the limb. The strap can hold the electrodes, which are electrically connected to the electrostimulationelectronics unit, against the patient's skin. The strap can be sized and shaped and formed of a material for flexibility and comfort, such as including a battery housing and an electronics housing arranged at different locations along the strap length to facilitate articulation when worn.

[0026] FIG. 1 depicts an example of a limb wearable neurostimulation device for treating at least one of RLS or PLMD. In an example, an electrostimulation therapy system can include a wearable electrostimulation device 102 including, e.g., an electrostimulation electronics unit 104, and one or more electrostimulation electrodes 106. For example, the wearable electrostimulation therapy device 102 can deliver electrostimulation therapy to skin of a subject via charge-dispersing materials such as the electrode pads 110, which help form the electrodes 106. In an example, the electrode pads 110 can be removably couplable to the wearable electrostimulation device 102. The electrode pads 110 can each be attached to a pairing surface 122 of the wearable electrostimulation device 102. The pairing surface 122 can include the electrode terminal 108 e.g., disposed therein, and the electrode terminal 108 can be electrically connected to the electrostimulation electronics unit 104. In an example, two or more electrode pads 110 are each paired to corresponding pairing surfaces 122 including one electrode terminals 108. In another example, one electrode pad 110 can be paired to an electrode pairing surface 122 containing more than one electrode terminal 108, or one electrode pad can span multiple electrode pairing surfaces 122 containing one or more electrode terminals 108. In an example, the electrode pad 110 can be removable for, e g., hygienic maintenance, electrode maintenance such as rehydrating, or disposal.

[0027] The wearable electrostimulation device 102 can be worn by the subject and can include or use the electrostimulation electronics unit 104 coupled to the electrodes 106, such as for transcutaneously delivering an electrostimulation signal. The wearable electrostimulation device 102 can be sized and shaped to be able to be attached or held to a body location of the subject, e.g., a leg, arm, foot, waist, neck, head, or chest of the subject. In an example, the wearable electrostimulation device 102 can include or use a strap to help hold the electrodes 106 to the skin of the subject. While electrodes aregenerally described herein with a focus on providing electrostimulation to a subject, the electrodes can alternatively or additionally be used such as to help detect or measure one or more biosignals or biopotentials from the subject. A particular electrode 106 can include or use an electrode terminal 108 and an electrode pad 110. For example, the electrode terminal 108 can receive a capacitively-coupled (e.g., coupled using series DC-blocking capacitors, e.g., in a charge-balanced arrangement) electrostimulation signal from the electrostimulation electronics unit 104, and can deliver a resulting electrostimulation signal to the skin of the subject, such as via the electrode pad 110. In an example, multiple electrodes, such as two electrodes 106, can be used. For a bipolar electrode example having two electrodes 106, this can a first electrode that can serve as an anode and a second electrode, such as which can serve as a cathode. Also, a plurality of electrodes 106 can be arranged to form a multi-electrode group, matrix, or array such as for one or both of sensing or for delivering the electrostimulation signal to the skin of the subject. In an example, each electrode terminal 108 can be an electrode contact fixed to the wearable electrostimulation device 102 and each corresponding electrode pad 110 can be removably couplable to the device 102. In other examples, the electrode pad can be fixed to the wearable electrostimulation device 102. Because the current density of the electrostimulation signal at the electrode terminal 108 may be larger than desired, the electrode pad 110 can include an embedded or other arrangement of electrical conductors that can help distribute the electrostimulation signal current over a larger effective surface area for delivery to the subject at the skin-electrode interface. The electrode pad can be formed of a hydrogel, a hydrophilic polymer such as polyvinyl alcohol (PVA), carbon, textiles, or other types of conductive or dielectric gels, a polymer, or a textile. In an example, two wearable electrostimulation devices 102 can be worn bilaterally, such as on different limbs of a patient to provide bilateral electrostimulation.

[0028] An individual wearable electrostimulation device 102 can include an electrostimulation electronics unit 104 communicatively coupled to the electrostimulation electrode(s) 106. The wearable electrostimulation device 102 can be worn by the subject and can include or use the electrostimulationelectronics unit coupled to the electrodes, such as for transcutaneously delivering an electrostimulation signal. Herein, the term high frequency electrostimulation (HFS) can refer to certain high-frequency (greater than 400 Hertz, such as greater than 1 kilohertz) electrostimulation waveforms capable of inducing tonic motor activation (TOMAC) when applied at an external target body location of the patient. This is distinct from other approaches to electrostimulation, such as TENS or implantable devices which operate at considerably different parameters which are generally not compatible with sleep or for treating RLS or PLMD, such as parameters that involve sensory perception of the patient and that do not induce TOMAC in a patient muscle. In an example, the HFS devices and methods herein include use of a capacitive coupling to apply HFS which induces TOMAC in a particular muscle without attempting to surround current injected in skin with a large opposite-current as in TENS paradigms in, e.g., evident during electromyogram monitoring.

[0029] FIG. 2A depicts an electrostimulation electronics unit for use as part of a neurostimulation device. The electrostimulation electronics unit 204 can be similar in many respects to the electrostimulation electronics unit 104 of FIG. 1. The components, structures, configuration, functions, etc. of unit 204 can therefore be the same as or substantially similar to that described in detail above with reference to unit 104. In an example, the electrostimulation electronics unit 204 can including a main printed circuit board (PCB) housing 214 and a batten- housing 216. In an example, the PCB housing 214 and the battery housing 216 can be located adjacent to each other, such as encased in a housing top 220 and housing bottom 224 of a casing or chassis of the electrostimulation electronics unit 204.

[0030] The electrostimulation electronics unit can include waveform generation circuitry (depicted in FIG. 2A as WGC 238) configured to supply an alternating current (AC) electrostimulation signal for delivery to the skin at an electrode-skin interface. The electrostimulation waveform can be supplied at a frequency between about 1kHz to about 10kHz such as for treating Restless Leg Syndrome (RLS) or Periodic Limb Movement Disorder (PLMD), such as described in Charlesworth U.S. Patent No. 11,103,591 and also as described in Raghunathan WIPO application numberPCT / US2024 / 024116, each of which are hereby incorporated by reference in their entirety. The electrostimulation electronics unit 204 can generate TOMAC excitation waveform for delivery, via the one or more electrodes, to the external target body location. Herein, the term “TOMAC excitation waveform" means a waveform having the parameters to induce tonic motor activation (e.g., activating proprioceptive afferents) in a patient muscle when applied at an exterior location of a patient (e.g., the outermost layer of patient skin). In an example, waveform generation circuitry 238 can generate a TOMAC waveform having a frequency between 400 Hertz (Hz) and 10,000 Hz and at a specified first current between 5 milliamperes (mA) and 50 mA. For example, the TOMAC waveform can be generated at a frequency within a range of about 1 kHz (kilohertz) and 5 kHz, or about 2 kHz. The TOMAC waveform can be generated via a power source supplying less than about 100 volts zero-to-peak voltage amplitude per phase, such as less than about 60 volts zero-to-peak voltage amplitude per phase. In an example, the TOMAC waveform can be generated having a duty cycle greater than about 25%, such as a duty’ cycle greater than about 40%, greater than about 50%, greater than about 75%, or greater than about 90%. In an example, the TOMAC waveform can deliver a specified root means squared (RMS) current (e.g., over a specified duration such as about 10 minutes (min), about 20 min, about 30 min, about 40 min, etc ). For example, the RMS current can be between about 10 mA and about 40 mA. This approach is distinct from that of other TENS devices, which generally exhibit an RMS current between about 3 mA and about 5 mA and involve much lower frequencies (e.g.. within a range of about 1 Hz to about 300 Hz) and lower duty cycles (e.g., within a range of about 2% to about 15%). The present inventors have recognized the benefits of delivering such a high frequency, high duty cycle current, including delivery of sufficient charge to induce TOMAC in the patient without discomfort or injury to the patient. Such a physiological response is not able to be induced by other electrostimulation approaches, such as TENS.

[0031] FIG. 2B depicts insertion of an electrostimulation electronics unit into an opening of a removable strap. In an example, the electrostimulation electronics unit 204 can be attached to, embedded within, or sized and shapedfor mating with a strap, sleeve, clamp, or band to help hold the electrodes to the skin of the subject, the strap / unit 204 forming limb wearable neurostimulation device 202. For example, as depicted in FIG. 2B, the electrostimulation electronics unit can be configured to couple with a removable strap 218. Alternatively or additionally, the wearable neurostimulation device 202 can include or use an adhesive or can connect to other items wearable by the subject, e.g.. hats, clothing, etc. Alternatively, the electrostimulation electronics unit 204 can be sufficiently wearable on the skin surface of the subject by adhesion forces of the electrodes alone without the need for additional features to help hold the unit to the subject, the unit 204 itself being the wearable neurostimulation device 202.

[0032] The wearable electrostimulation device 202 can be attached or held to (e.g., via the removable strap 218) a body location of the subject, e g., a leg, arm, foot, waist, neck, head, or chest of the subject at an external body location corresponding with a nerve target (e.g., at or near a peroneal nerve, at or near a sural nerve, etc.) of the subject skin for transcutaneous electrostimulation thereof. In an example, the electrostimulation electronics unit 204 can be insertable though an opening 212 of the removable strap 218, such as to facilitate end-user entry and removal of the unit 204 into the removable strap 218. In an example, the removable strap 218 can be user-washable, such as made of a material that is machine washable without deforming or damaging the neurostimulation device 202. The use of a removable strap 218 can promote longevity of the neurostimulation device 202. such that the removable strap 218 can be replaced at a greater frequency than the electrostimulation electronics unit 204 over the course of months or years of neurostimulation therapy.

[0033] FIG. 2C depicts an example of a limb wearable neurostimulation device for treating at least one of RLS or PLMD. The neurostimulation device 202 can be similar in many respects to the wearable electrostimulation device 102 of FIG. 1. The components, structures, configuration, functions, etc. of the neurostimulation device 202 can therefore be the same as or substantially similar to that described in detail above with reference to the device 102. The neurostimulation device 202 as a whole can be a wearable solution, such asfeaturing an elongate strap (e.g., the removable strap 218) that can substantially encircle the limb. The strap can be resizable to fit a plurality’ of different limb sizes, such as adjustable via a hook-and-loop connection, a buckle, a clip, etc. The neurostimulation device 202 as a whole can be substantially stretchable or resilient in at least one dimension, so as to be adaptable to general or specific wearers per unit of time. For example, the device may include an elongate portion, and the neurostimulation device may be provided as a bendable or articulated zone along the elongate portion, such that the strap is substantially conformal to a limb contour (e.g., around a human calf portion of a leg). In an example, the strap can be sized and shaped and formed of a material for flexibility and comfort, such as including a battery housing and an electronics housing arranged at different locations along the strap length to facilitate articulation when worn. The strap can hold the electrodes (e.g., including or attached to the electrode terminals 208), which are electrically connected to the electrostimulation electronics unit 204, against the patient's skin.

[0034] FIG. 2D is an exploded view of an example of a limb wearable neurostimulation device for treating at least one of RLS or PLMD. In an example, the neurostimulation device 202 can include or use a removable strap 218, electrode pads 210 (e.g., for electrical connection with respective electrode terminals 208), and an electrostimulation electronics unit 204 including a housing top 220, a housing bottom 224, main PCB 228, a flexible printed circuit board 222 (also herein called a flex circuit 222), and a battery 226. In an example, the neurostimulation device 202 can include one or more intermediate layers, such as one or more rubber contact layers 234 arranged facilitate transfer of end-user button pressing to, e.g., a contact on the main PCB 228.

[0035] Generating the above-described TOMAC excitation waveform that is compatible with sleep, particularly in a wearable, battery’ operated device, can be challenging in terms of heat dissipation, power consumption, efficiency, and therapeutic efficacy. For example, several electrostimulation and thermal regulation parameters (e.g., frequency, RMS current as a function of duty cycle, battery size, heat dispersion from to the patient from theneurostimulation device 202, total charge delivered to the patient, slew rate, can be described as "interdependent" parameters or mutually dependent variables. The neurostimulation device 202 involves optimizations which balance certain “trade-offs” of inherent factors in neurostimulation to arrive at an effective, safe, and portable (e.g., for use in at-home therapy) treatment for RLS or PLMD.

[0036] HFS, while providing a comfortable and efficacious waveform to patient skin, such benefits are provided at the “cost” of certain challenges. First, HFS involves significantly higher reactive power loss at an electrodeskin interface, due to a capacitance of human skin. For example, HFS can involve up to about 20X more reactive power loss than certain TENS waveforms, such as meeting a capacitive load within a range of about 5 nanofarads (nF) and about 150 nF, such as a skin tissue having a capacitance greater than about 100 nF). The present techniques to delivery of HFS, via the “TOMAC excitation waveform" involves (e.g., when compared to TENS and implantable neurostimulation) a relatively high amount of charge delivered per second (e.g.. within a range of about 0.001 to about 0.04 coulombs per second) and at a relatively small charge per phase (about 1.25E- 7 to 5E-6 coulombs per phase, e.g., within a range of about 0.1 to about 5 micro-coulombs per phase) such as depending on a duty cycle of the waveform. Such relatively high amounts of charge, alongside a relatively high RMS current (e.g., related to a duty cycle greater than about 25%) can overcome such the reactive power loss at the electrode-skin interface and thus overcome the capacitance of human skin despite the challenge of HFS.

[0037] To help promote the above benefits, the electrostimulation electronics unit 204 can include waveform generation circuitry to produce the TOMAC excitation waveform with a slew rate of less than about 25 microseconds (ps) rise-time and, alternatively or additionally, less than about 25 ps fall-time. Here, the slew rate of less than about 25 ps fall-time can be considerably faster than a typical capacitive discharge of a TENS device, which directly results in more total energy dispersed per phase. This, and optionally controlling a duty cycle of the TOMAC excitation waveform to be relatively high (e.g., a duty cycle greater than about 25%, such as a duty cycle greater than about40%, greater than about 50%, greater than about 75%, or greater than about 90%) can promote a greater amount of charge delivered to the patient skin when compared to other approaches, such as to help overcome certain challenges of HFS. Finally, a target current (e.g., within a range of about 10 mA to about 40 mA) can be specified such that the target current is sufficiently high for the patient to receive a therapeutic benefit (e.g., TOMAC) while also sufficiently low as to not cause discomfort or other side effects.

[0038] The above specified parameters - driving HFS driving HFS, at high total energy, with rapid up / down slew-rates, into a physiological load with an inherently capacitive property, can result in uniquely high amounts of AC Reactive Load in a medical device as compared to other TENS or implantable devices. For example, a combined (e.g., resistive and reactive) nature of the target tissue can reflect or return power to the therapy -producing circuit, which must dissipate the resulting heat; yet also stay below desired temperature thresholds to promote a safety of a body-worn medical device.

[0039] In an example, the neurostimulation device 202 can include a thermal management system configured to address the above-identified thermal challenges with producing the TOMAC excitation waveform. For example, the electrostimulation electronics unit 204 can include or use a heat sink or insulating cover arranged such as to receive thermal conduction from components (e.g., transistors, switches, etc. ) of the PCB 228. For example, the heat sink can include a dispersion structure integrated into the flex circuit 222 that also includes the interconnect 232 for the electrode terminals 208.

[0040] FIG. 3A depicts a connection side of flexible printed circuit board of an example of an electrostimulation electronics unit. FIG. 3B is a top view showing a mating of a connection side of a flexible printed circuit with a main printed circuit board of an example of an electrostimulation electronics unit. FIG. 3C is a perspective view showing a mating of a connection side of a flexible printed circuit with a main printed circuit board of an example of an electrostimulation electronics unit.

[0041] In an example, to promote a desired heat dissipation, a layout of the PCB 228 can be arranged such that one or more thermally radiating components 302 are substantially concentrated or aligned on the PCB 228,such as arranged toward a periphery of the PCB 228. In an example, the one or more thermally radiating components 302 can include transformers, switching power transistors, detection and signal processing integrated circuits (ICs), microcontrollers, etc. Here, the heat sink or insulating cover can include a dispersion structure, such as included on a surface of the flex circuit 222. The dispersion structure 312 on the flex circuit 222 can include one or more thermal conduction contacts 230 for interfacing with respective thermally radiating components 302, such as to spread and dissipate heat effectively. For example, the dispersion structure 312 of the flex circuit 222 can help facilitate transfer of thermal energy (e.g., via the heat sink) from the PCB at a rate greater than 0.2 Joules per second (J / sec), ensuring efficient heat dissipation during operation and even dispersion of the heat across the patient skin to avoid uncomfortable point source heating of the device. In an example, the dispersion structure 312 can be embedded with a material having a thermal conductivity greater than 100 Watts per meter-Kelvin (W / mK), such as copper, aluminum, silver, gold, or a thermal polymer, or a combination thereof. In an example, the interconnect 232 can be arranged substantially toward an outer edge of the dispersion structure 312, e.g., such that it does not divide a significant portion of the dispersion structure 312 and to promote transfer of thermal energy via the dispersion structure 312. As depicted in FIG. 3B, the flex circuit 222 can be sized and shaped such as to mate with a top face of the PCB 228, e.g., such that the thermal conduction contacts 230 makes physical contact with respective thermally radiating components 302 and such that the interconnect 232 is electrically connected to the PCB 228, e.g., via insertion into a port 236.

[0042] FIG. 4A depicts an example of housing a circuitry unit and a battery in an example of an electrostimulation electronics unit. FIG. 4B depicts a thermally conductive foil enclosing a circuitry unit and a battery in an example of an electrostimulation electronics unit.

[0043] As depicted in FIG. 4A, the battery 226 can be housed by the battery housing 216, such as including top and bottom portions battery housing 216. Similarly a circuitry unit 404 (e.g., including the PCB 228 as depicted in FIG. 3 A, FIG 3B, and FIG. 3C) can be housed by a circuitry housing 402, such ashoused by top and bottom portions of the circuitry housing 402. As depicted in FIG. 4 A, the battery housing 216 and the circuitry housing 402 can be separate, such as configured to be arranged within the electrostimulation electronics unit (e.g., unit 104, 204 of FIG. 1 and FIG. 2C, respectively) at different locations along a strap length (e.g., along the removable strap 218) such as to allow articulation between electronics housing and the battery housing. As depicted in FIG. 4B, the battery 226 and the circuitry unit 404 (and also the battery housing 21 and the circuitry housing 402) can be at least partially wrapped, enveloped, or enclosed in a thermally-conductive foil 408. For example, the thermally-conductive foil 408 can be formed of copper, aluminum, silver, gold, or a thermal polymer, or a combination thereof. Here, the thermally-conductive foil 408 can act as a thermal radiating structure and can be configured to vent thermal energy from at least one of the battery 226 or the circuitry unit 404. In an example, the foil can exhibit flexibility in a region between the circuitry unit 404 and the battery 226 (and their respective housings), such as to allow articulation between the circuitry unit 404 and the battery 226 when the strap of the neurostimulation device (e.g., wearable electrostimulation device 102 of FIG. 1 or limb-wearable neurostimulation device 202 of FIG. 2C) is placed on and encircles a patient limb.

[0044] FIG. 5 is a flowchart of a process for treating Restless Leg Syndrome (RLS) or Periodic Limb Movement Disorder (PLMD) using a limb wearable neurostimulation device. For example, the process can be carried out via use of the wearable electrostimulation device 102 (shown in FIG. 1) or the limbwearable neurostimulation device 202 (shown in FIG. 2C) and can be performed, e.g., via the processor 602 of the machine 601 (shown in FIG. 6).

[0045] At 502, a tonic motor activation (TOMAC) excitation waveform can be generated, e.g., by a waveform generator of an electrostimulation electronics unit included in a wearable electrostimulation device. This waveform can be generated onboard the wearable device, such as generated via a waveform generator implemented on a printed circuit board (PCB) within the wearable device. This waveform can be established or adjusted such as to deliver constant current at a frequency between 1,000 Hz and 5,000 Hz, with a zero-to-peak current amplitude ranging from 10 mA to 50 mA. Inan example, the waveform can be established or adjusted to maintain a minimum duty cycle of at least 25% throughout a therapy session.

[0046] At 504, the waveform can be delivered, e.g., via electrodes of the wearable electrostimulation device, to an external target body location on the limb, eliciting a motor activation (TOMAC) in the limb. For example, the TOMAC can include activating proprioceptive afferents of patient neurons. The TOMAC excitation waveform can be controlled to deliver a specified amount of charge to the patient's skin. For example, the waveform can be controlled to deliver within a range of 0.1 to 5 micro-coulombs per phase (pC / phase) or 0.001 to 0.04 Coulombs per second (C / s). In an example, the waveform can be controlled such as to mitigate a reactive power loss related to a capacitive load of at least lOOnF. In an example, the TOMAC excitation waveform can be controlled to have a slew rate of less than 25 microseconds (ps) for at least one of a rise-time or a fall-time.

[0047] At 506, thermal conduction, from components arranged on the PCB, can be received to regulate a thermal output of the wearable neurostimulation device. For example, the thermal conduction can be received via a heat sink or insulating cover within the electrostimulation electronics unit. In an example, heat can be distributed (e.g., via a dispersion structure of a heat sink) across a surface area larger than the PCB's footprint. In an example, thermal energy can be transferred away from the PCB at a rate greater than about 0.2 Joules per second (J / sec).

[0048] In an example, an indication of temperature can be received (e.g., via one or more temperature sensors) from a neurostimulation device temperature during therapeutic operation, such as providing real-time temperature feedback. The indication of temperature can be used such as to establish or adjust at least one parameter of the TOMAC excitation waveform (e.g., duty7cycle, frequency, current amplitude, etc.). For example, the TOMAC excitation waveform can be controlled such as having a variable duty-cycle pulse-width modulated (PWM) waveform. Here, the duty cycle can be dynamically adjusted, e.g., based on the real-time temperature feedback such as to regulate a device temperature within a safe range, e.g., to help ensure thewearable electrostimulation device does not exceed a patient body temperature by more than 6 degrees Celsius.

[0049] FIG. 6 illustrates generally an example of a block diagram of a machine 601 upon which any one or more of the techniques (e.g., methodologies) discussed herein may perform in accordance with some examples. In alternative embodiments, the machine 601 may operate as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine 601 may operate in the capacity' of a server machine, a client machine, or both in server-client network environments. In an example, the machine 601 may act as a peer machine in peer-to-peer (P2P) (or other distributed) network environment. The machine 601 may be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a web appliance, a network router, switch or bridge, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term ‘‘machine” shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), other computer cluster configurations.

[0050] Examples, as described herein, may include, or may operate on. logic or a number of components, modules, or mechanisms. Modules are tangible entities (e.g., hardware) capable of performing specified operations when operating. A module includes hardware. In an example, the hardware may be specifically configured to carry out a specific operation (e.g., hardwired). In an example, the hardware may include configurable execution units (e.g., transistors, circuits, etc.) and a computer readable medium containing instructions, where the instructions configure the execution units to carry out a specific operation when in operation. The configuring may occur under the direction of the executions units or a loading mechanism. Accordingly, the execution units are communicatively coupled to the computer readable medium when the device is operating. In this example, the execution unitsmay be a member of more than one module. For example, under operation, the execution units may be configured by a first set of instructions to implement a first module at one point in time and reconfigured by a second set of instructions to implement a second module.

[0051] Machine (e.g., computer system) 601 may include a hardware processor 602 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 603 and a static memory 604, some or all of which may communicate with each other via an interlink (e.g., bus) 605. The machine 601 may further include a display unit 606. an alphanumeric input device 607 (e.g., a keyboard), and a user interface (UI) navigation device 608 (e.g., a mouse). In an example, the display unit 606, alphanumeric input device 607 and UI navigation device 608 may be a touch screen display. The machine 601 may additionally include a storage device (e.g., drive unit) 609, a signal generation device 610 (e.g., a speaker), a network interface device 611, and one or more sensors 612, such as a global positioning system (GPS) sensor, compass, accelerometer, or other sensor. The machine 601 may include an output controller 616. such as a serial (e.g.. universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate or control one or more peripheral devices (e.g., a printer, card reader, etc.).

[0052] The storage device 609 may include a machine readable medium 613 that is non-transitory on which is stored one or more sets of data structures or instructions 614 (e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. The instructions 614 may also reside, completely or at least partially, within the main memory 603. within static memory 604, or within the hardware processor 602 during execution thereof by the machine 601. In an example, one or any combination of the hardware processor 602. the main memory 603, the static memory 604, or the storage device 609 may constitute machine readable media.

[0053] While the machine readable medium 613 is illustrated as a single medium, the term ‘‘machine readable medium'’ may include a single mediumor multiple media (e.g., a centralized or distributed database, or associated caches and servers) configured to store the one or more instructions 614.

[0054] The term “machine readable medium” may include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine 601 and that cause the machine 601 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding or carry ing data structures used by or associated with such instructions. Nonlimiting machine-readable medium examples may include solid-state memories, and optical and magnetic media. Specific examples of machine- readable media may include: non-volatile memory, such as semiconductor memory devices (e g.. Electrically Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory7(EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD- ROM disks.

[0055] The instructions 614 may further be transmitted or received over a communications network 615 using a transmission medium via the network interface device 611 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), Plain Old Telephone (POTS) networks, and wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®. IEEE 602.16 family of standards known as WiMax®). IEEE 802.15.4 family of standards, peer-to- peer (P2P) networks, among others. In an example, the network interface device 611 may include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network 615. In an example, the network interface device 611 may include a plurality of antennas to wirelessly communicate using at least one of singleinput multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. The term “transmissionmedium” shall be taken to include any intangible medium that is capable of storing, encoding or carrying instructions for execution by the machine 601, and includes digital or analog communications signals or other intangible medium to facilitate communication of such software.

[0056] The following, non-limiting examples, detail certain aspects of the present subject matter to solve the challenges and provide the benefits discussed herein, among others.

[0057] The above Detailed Description can include references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

[0058] In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls. In this document, the terms “including” and “in which” are used as the plain- English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that can include elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim.

[0059] In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one. independent of any other instances or usages of “at least one” or “one or more.” In this document, theterm “or’" is used to refer to a nonexclusive or, such that “A or B” can include "‘A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms '‘including” and “in which” are used as the plain- English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that can include elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.

[0060] The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) can be used in combination with each other. Other embodiments can be used, such as by one of ordinary’ skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features can be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter can lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

CLAIMSWhat is claimed is:

1. A limb wearable neurostimulation device for treating at least one of RLS or PLMD, the device comprising: an electrostimulation electronics unit, including: a substrate including a neurostimulation electrical waveform generator, configured to generate a tonic motor activation (TOMAC) excitation waveform to elicit TOMAC in the limb during delivery of the waveform by electrodes to patient skin, the waveform configured for delivery at a constant current, a frequency in a range of 1,000 Hz to 10,000 Hz, a zero-to-peak current amplitude within a range of 10 milliamperes (mA) and 50 mA; an electronics housing to house one or both of electronics carried on the substrate or a battery' to power to electronics carried on the substrate; and a heat sink or insulating cover arranged within the electrostimulation electronics unit to receive thermal conduction from components arranged on the substrate and to regulate a thermal output of the electronics housing.

2. The device of claim 1, wherein the device includes an elongate strap, defining a strap length and a strap width together defining a strap area footprint, the strap of a length to substantially encircle the limb, the strap configured to hold electrodes electrically connected to the electrostimulation electronics unit against patient skin.

3. The device of claim 2, wherein the heat sink or insulating cover includes a conformal thermally-conductive foil wrapped around the battery housing and the electronics housing to, the foil having flexibility in a region between the electronics housing and the battery housing to allow articulation between the electronics housing and the battery housing when the strap is placed on and encircles the limb.

4. The device of claim 2, wherein the battery housing and the electronics housing are arranged at different locations along the strap length to allow articulation between electronics housing and the batten7housing.

5. The device of claim 1, wherein: the substrate is a printed circuit board (PCB) includes plurality of substantially thermally radiating components including at least one of at least transformer and switching power transistors arranged toward a periphery' of the PCB; and the heat sink or insulating cover includes a dispersion structure including a thermal conduction contact to the plurality of substantially thermally7radiating components at the periphery and configured to spread and dissipate heat.

6. The device of claim 5, wherein the dispersion structure is sized and shaped to spread and dissipate the heat across a surface area greater than a footprint of the PCB.

7. The device of claim 5, wherein the dispersion structure is included in a flex circuit including an interconnect electrically connecting the electrodes to the PCB.

8. The device of claim 7, wherein the dispersion structure is embedded with a material having a thermal conductivity greater than 100 Watts per meter- Kelvin (W / mK) and the interconnect is arranged toward an outer edge of the dispersion structure.

9. The device of claim 1, wherein: the electrostimulation electronics unit includes one or more temperature sensors, configured to measure a temperature at the device including while the device is in use delivering neurostimulation to the limb, the one or more temperature sensors providing an electrical signal representative of the measured temperature; andthe TOMAC excitation waveform is generated as at least one of a variable duty-cycle pulse-width modulated (PWM), a variable frequency, or a variable amplitude TOMAC excitation waveform.

10. The device of claim 9, comprising waveform modulation circuitry configured to adjust at least one of the duty-cycle, the amplitude, or the frequency at least in part based on the electrical signal representative temperature to maintain the temperature within a range such that the temperature does not exceed body temperature by more than 6 degrees Celsius.

11. The device of claim 1, comprising a battery housing separate from the electronics housing, carry ing a battery7to power electronics carried on the substrate.

12. The device of claim 1, wherein the heat sink or insulating cover is connected to ground node or fixed reference node to shield noise, wherein the heat sink or insulating cover serves as ground plane.

13. The device of claim 1 , wherein the TOMAC excitation waveform is configured for delivery7to the patient skin within a range of 0.1 to 5 microcoulombs per phase (pC / phase).

14. The device of claim 1 , wherein the TOMAC excitation waveform is configured for delivery7to the patient skin within a range of 0.001 to 0.04 Coulombs per second (C / s).

15. The device of claim 1, wherein the TOMAC excitation waveform is configured for delivery to patient skin to elicit TOMAC in the limb, despite reactive power loss related to a capacitive load of at least lOOnF.

16. The device of claim 15, wherein the capacitive load is provided by a natural capacitance of human skin.

17. The device of claim 1. wherein the TOMAC excitation waveform is configured for delivery to patient skin at a slew rate less than 25 microsecond (ps) rise-time and less than 25 ps fall-time.

18. The device of claim 1, wherein the heat sink or insulating cover is configured to transfer thermal energy from the substrate at a rate greater than 0.2 Joules per second (J / sec).

19. A method for treating at least one of RLS or PLMD via limb wearable neurostimulation device, the method comprising: generating, via a substrate including a neurostimulation electrical waveform generator, a tonic motor activation (TOMAC) excitation w aveform having a constant current, a frequency in a range of 1,000 Hz to 5,000 Hz, a zero-to-peak current amplitude within a range of 10 milliamperes (mA) and 50 mA; delivering, via electrodes, the TOMAC excitation waveform, via to an external target body location on the limb to elicit TOMAC in the limb; receiving, via a heat sink or insulating cover arranged w ithin the limb wearable neurostimulation device, thermal conduction from components arranged on the substrate, including regulate a thermal output of the wearable neurostimulation device.

20. The method of claim 19, comprising: contacting a plurality of substantially thermally radiating components, including at least one of at least transformer and switching pow er transistors arranged tow ard a periphery of the substrate, via a thermal conduction contact of the heat sink; and spreading and dissipating the heat across a dispersion structure.

21. The method of claim 20, wherein the dispersion structure is sized and shaped to spread and dissipate the heat across a surface area greater than a footprint of the substrate.

22. The method of claim 20, wherein the dispersion structure is included in a flex circuit including an interconnect electrically connecting the electrodes to the substrate.

23. The method of claim 22, wherein the dispersion structure is embedded with a material having a thermal conductivity greater than 100 Watts permeter-Kelvin (W / mK) and the interconnect is arranged toward an outer edge of the dispersion structure.

24. The method of claim 19, comprising: measuring, via a temperature sensor, a temperature at the device the delivering the TOMAC excitation waveform to the external target body location, receiving, from the temperature sensor, an electrical signal representative of the measured temperature; and adjusting a duty’ cycle of the TOMAC excitation waveform at least in part based on the electrical signal representative temperature to maintain the temperature within a range such that the temperature does not exceed body temperature by more than 6 degrees Celsius.

25. The method of claim 19, wherein the delivering the TOMAC excitation waveform to an external target body location includes a delivery of charge to the external target body location within a range of 0.1 to 5 micro-coulombs per phase (pC / phase).

26. The method of claim 19, wherein the delivering the TOMAC excitation waveform to an external target body location includes a delivery’ of charge to the external target body location within a range of 0.001 to 0.04 Coulombs per second (C / s).

27. The method of claim 19, wherein the delivering the TOMAC excitation waveform to an external target body location includes a delivery of charge includes mitigating a reactive power loss related to a capacitive load of at least lOOnF.

28. The method of claim 27, wherein the capacitive load is provided by a natural capacitance of human skin.

29. The method of claim 19, wherein the delivering the TOMAC excitation waveform to an external target body location includes a delivery’ to the external target body location at a slew rate less than 25 microsecond (ps) rise-time and less than 25 ps fall-time.

30. The method of claim 19, wherein receiving, via a heat sink or insulating cover arranged within the limb wearable neurostimulation device, thermal conduction from components arranged on the substrate includes transferring thermal energy from the substrate at a rate greater than 0.2 Joules per second (J / sec).

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