WO2022035740A1

WO2022035740A1 - Systems and methods for duty cycle interferential current stimulation and therapy

Info

Publication number: WO2022035740A1
Application number: PCT/US2021/045181
Authority: WO
Inventors: James Howard KLETT
Original assignee: Klett James Howard
Priority date: 2020-08-10
Filing date: 2021-08-09
Publication date: 2022-02-17

Abstract

Systems and methods for duty cycle interferential current stimulation and therapy are disclosed herein. In one embodiment, a system for electrical stimulation or therapy of a user includes: a first pair of contacts configured for contacting an area of user's skin; a second pair of contacts configured for contacting the area of user' s skin; and a generator of electrical voltage that is configured for providing a first waveform at a first frequency to the first pair of contacts and a second waveform at a second frequency to the second pair of contact. Interactions of the first waveform and the second waveform generate a resulting waveform at a heterodyne frequency at the area of user's skin. The resulting waveform is controlled as a duty cycle. A start of an ON phase of the duty cycle is synchronized with a start of an absolute refractory period of a target nerve, and a start of an OFF phase of the duty cycle is synchronized with a start of a relative refractory period of the target nerve.

Description

SYSTEMS AND METHODS FOR DUTY CYCLE INTERFERENTIAL CURRENT STIMULATION AND THERAPY

CROSS-REFERENCE(S) TO RELATED APPLICATION(S)

The present application claims the benefit of a US Provisional Application No. 63/063,580 filed on August 10, 2020.

TECHNICAL FIELD

The present invention relates generally to patient stimulation and therapy by electrical current and more specifically to delivering stimulation and therapy synchronously with the user’s neural response.

BACKGROUND

It is known that electrical current may stimulate a patient’s muscles to contract or reduce pain of the patient. However, large amounts of electrical current delivered into the patient’s body create safety concerns. Some of the unwanted side effects of high electrical current delivered to the patient are skin burns at the treatment site, electrocution, disruptive transcranial stimulation, and carotid artery closure to name a few.

In some conventional technologies, two electrical current waveforms at different frequencies fl and 12 are combined to create an interferential current stimulation. For example, one waveform may have a frequency fl, and the other waveform may have a frequency f2. When interfering, the two waveforms generate a resulting waveform having a frequency fl - 12, f2 - fl, fl + f2, or some other combination of frequencies fl and 12 (also known as heterodyne combinations of frequencies). Such combinations of electrical currents at different frequencies are referred to as interferential current stimulation (IFCS). Nevertheless, even with IFCS the problems of electrocution, skin burns, fatigued tissue, disruptive transcranial stimulation, carotid artery closure, etc., may persist. Accordingly, improved systems and methods are needed for patient stimulation and therapy by electrical current.

SUMMARY

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 of the claimed subject matter.

Briefly, the inventive technology is directed to improving patient’s experience during electrical current therapy or stimulation. The inventive technology may be used for pain management, fecal and urinary incontinence, muscle relaxation, pre-menstrual and menstrual pain, dysphagia, and other purposes. In some embodiments, an electrode having two pairs of contacts is attached to the user’s skin. The pairs of contacts are coupled to corresponding pairs of electrical wires or contacts that provide two independent electrical waveforms to the electrode. These electrical waveforms may be emitted at slightly different frequencies, for example, 4100 Hz (fl) and 4000 Hz (f2). In operation, the waveforms interact within the area of skin under the electrode to generate, for example, a heterodyne frequency fl-f2 = 100 Hz. In different embodiments, the fl may be 1,000 Hz to 20,000 Hz, and f2 may be 1,000 Hz to 20,000 Hz. The resulting beat frequency (also referred to a heterodyne frequency) may have various therapeutic, stimulating or soothing effects on the user.

Generally, human neurons (also referred to as cell bodies, nerve cells, or motor neurons) have several phases of activation and deactivation. When the neuron is not stimulated such neuron is at rest, therefore being at its resting potential. When the neuron is first stimulated, its action potential (e.g., its pain inhibiting potential) is triggered and travels along the neural pathways. This phase is called a depolarizing or activation phase, and it takes place during the absolute refractory period. In the next phase, the potential of the neuron decreases during the re-polarization where the action potential of the neuron returns back to its resting potential. Next, a certain amount of undershoot occurs in the neuron during the hyper polarization undershoot, where the action potential of the neuron first falls below the resting potential and then rises to the resting potential. Collectively, the re-polarization and hyper polarization phases of the neuron’s action potential are referred to as a relative refractory period. For a neuron to again become sensitive to stimulation after the initial stimulus that triggers a de-polarization phase, such neuron first has to go through its re-polarization and hyper polarization phases during the relative refractory period. Accordingly, during the relative refractory period the neuron is not sensitive to additional stimulation unless the additional stimulation is significantly greater than the initiating stimulation.

In some embodiments of the present technology, timing of the electrical current waveforms is synchronized with the absolute refractory period and relative refractory period of the neuron’s action potential. For example, the two waveforms that interact by combining into a target heterodyne or beat frequency may be emitted during the absolute refractory period (or mostly during the absolute refractory period), followed by not transmitting the waveforms during the relative refractory period. In some embodiments, such ON/OFF waveform transmission may be achieved by a duty cycle having its ON phase during the absolute refractory period (typically within a range of ,5mS to 1.5mS) and OFF state during the relative refractory period (typically within a range of 3.5 mS to 4.5 mS) resulting in an 8% to 75% duty cycle. Other sample duty cycles may apply in different scenarios. As a result, the amount of electrical current entering the user’s body is reduced, therefore avoiding negative side-effects of excessive electrical current, while preserving the beneficial effect of the electrical current treatment. Additionally, source battery power may be conserved, and/or signal generator may use fewer or smaller size batteries. Under a different scenario, by transmitting electrical current only during the absolute refractory period, the intensity of electrical current/voltage may in some situations be increased during the absolute refractory period while still keeping the average current/voltage under a desired safety and comfort threshold for the entire duration of absolute/relative refractive periods.

In some embodiments, electrical current stimulus at heterodyne or beat frequency can be delivered through electrical stimulators that are attachable to user’s skin. Such stimulators may have a stimulator electrode that is in contact with the user’s skin via hydrogel adhesive on one side, and in magnetic contact with a signal generator on the other side. The stimulator may have its own source of energy, for example, a battery. In operation, the stimulator may be repositioned from one place to another by the user.

In one embodiment, a system for electrical stimulation or therapy of a user includes: a first pair of contacts configured for contacting an area of user’s skin; a second pair of contacts configured for contacting the area of user’s skin; and a generator of electrical voltage configured for providing a first waveform at a first frequency to the first pair of contacts and a second waveform at a second frequency to the second pair of contacts. The interactions of the first waveform and the second waveform generate a resulting waveform at a heterodyne frequency at the area of user’s skin. The resulting waveform is controlled as a duty cycle. A start of an ON phase of the duty cycle is synchronized with a start of an absolute refractory period of a target nerve, and a start of an OFF phase of the duty cycle is synchronized with a start of a relative refractory period of the target nerve. In one aspect, a duration of the ON phase of the duty cycle corresponds to the absolute refractory period of the target nerve, and a duration of the OFF phase of the duty cycle corresponds to the relative refractory period of the target nerve.

In one aspect, the absolute refractory period is about .25 to 1.75 mS, the relative refractory period is about 3.25 to 4.75 mS, and the duty cycle is about 5% to 37%

In one aspect, the heterodyne frequency is a difference between the first frequency and the second frequency.

In one aspect, the first frequency is 1,000 Hz to 20,000 Hz, and the second frequency is 1,000 Hz to 20,000 Hz.

In one aspect, the first pair of contacts and the second pair of contacts are carried by a stimulator electrode that is magnetically and electrically coupled with a signal generator.

In one aspect, the first waveform and the second waveform are transmitted through magnets of the stimulator electrode to the area of user’s skin.

In another aspect, the first pair of contact and the second pair of contacts comprise a dispersive film configured for contacting the area of user’s skin.

In one aspect, the signal generator is detachable from the stimulator electrode.

In another aspect, the signal generator is configured for wireless communication with a mobile device.

In one embodiment a method for electrical stimulation or therapy of a user includes: generating a first waveform at a first frequency by a generator of electrical voltage; generating a second waveform at a second frequency by the generator of electrical voltage; transmitting the first waveform to a first pair of contacts configured for contacting an area of user’s skin; and transmitting the second waveform to a second pair of contacts configured for contacting the area of user’s skin. Interactions of the first waveform and the second waveform generate a resulting waveform at a heterodyne frequency at the area of user’s skin. The method also includes controlling the resulting waveform as a duty cycle, where a start of an ON phase of the duty cycle is synchronized with a start of an absolute refractory period of a target nerve, and a start of an OFF phase of the duty cycle is synchronized with a start of a relative refractory period of the target nerve.

In one aspect, a duration of the ON phase of the duty cycle corresponds to the absolute refractory period of the target nerve, and a duration of the OFF phase of the duty cycle corresponds to the relative refractory period of the target nerve.

In another aspect, a duration of the ON phase of the duty cycle is equal or shorter than a duration of the absolute refractory period of the target nerve, and a duration of the OFF phase of the duty cycle is equal or longer than the relative refractory period of the target.

In one aspect, the first pair of contact and the second pair of contacts are carried by a stimulator electrode, and the method also includes magnetically and electrically coupling the stimulator electrode with a signal generator.

In one aspect, the method also includes wirelessly providing instructions to the signal generator by a mobile device.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of the inventive technology will become more readily appreciated as the same are understood with reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: FIGURE l is a perspective view of a system for administering electrical stimulation in accordance with the present technology.

FIGURE 2 is a view of connectors for administering electrical stimulation in accordance with an embodiment of the present technology.

FIGURES 3, 3A, 3B, 4, 4A, 4B, 5, 5A and 5B are plan views of stimulator electrodes in accordance with embodiments of the present technology.

FIGURE 6 illustrates a stimulator in accordance with an embodiment of the present technology.

FIGURES 7A-7D are side views of a stimulator in accordance with embodiments of the present technology.

FIGURES 7E-7F are side views of a stimulator in accordance with embodiments of the present technology.

FIGURES 8A-8C are different views of a stimulator electrode in accordance with embodiments of the present technology.

FIGURES 9A-9C are different views of a signal generator in accordance with embodiments of the present technology.

FIGURES 9D-9G are different views of the bottom of a signal generator in accordance with embodiments of the present technology.

FIGURE 10 is a graph of waveforms in accordance with an embodiment of the present technology.

FIGURE 11 is a graph of mixed waveforms in accordance with an embodiment of the present technology.

FIGURE 12 is a graph of waveforms in operation in accordance with an embodiment of the present technology. FIGURES 13 and 13A are graphs of waveforms with duty cycle in accordance with embodiments of the present technology.

FIGURE 13 A is a graph of waveforms with duty cycle and a sEMG sensing window in accordance with an embodiment of the present technology. FIGURE 14 is a graph of stages of neural response in accordance with an embodiment of the present technology; and

FIGURES 15 and 15A are graphs of timing of the electrical current waveforms in accordance with embodiments of the present technology.

DETAILED DESCRIPTION

While several embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the claimed subject matter.

FIG. 1 is a perspective view of a system 100 for administering stimulation in accordance with the present technology. FIG. 1 shows a signal generator (also referred to as a stimulation generator) 1 that is electrically coupled to a stimulator electrode 2 with leadwires 3. In operation, the stimulator electrode 2 (also referred to as the electrode or the electrode body) adheres to the user’s skin via conductive hydrogel as the el ectrode/ skin interface medium to transmit electrical signals (current, voltage) whereby the user can experience beneficial therapeutical or stimulation effects.

The illustrated leadwires 3 are organized into two pairs: one pair of leadwires for transmitting first stimulation signal (e.g., stimulation waveforms) at frequency fl from connectors 8 to electrode socket connectors (e.g., snap fitting electrodes) 9, and the other pair of leadwires for transmitting second stimulation signal at frequency f2 from connectors (e.g., socket fittings) 6 to electrode sockets (connectors) 7. In different embodiments, different shapes and types of connectors and sockets may be used. In an embodiment, the leadwires 3 may plug into the signal generator 1 through a combination of connector 4 and connector jack 5. In operation, user may select desired waveforms using controls on the signal generator 1. A non-limiting example of leadwires and associated connectors is illustrated in FIG. 2.

FIGS. 3, 3A, 3B, 4, 4A, 4B, 5, 5A and 5B are plan views of electrodes 2 (also referred to as a stimulator electrode body) in accordance with embodiments of the present technology. The illustrated electrodes 2 have unibody construction, but in other embodiments separated or separable electrodes having just one connector per the electrode may also be used. FIG. 3 illustrates a unibody stimulator electrode 2 with four dispersion pads. Electrical current may be delivered through a combination of snap connectors 8 with snap fittings 9 embedded in the electrode 2, and pin connectors 7 with socket fittings 6. Illustrated unibody stimulator electrode 2 has an opening in the middle. FIGS. 3A and 3B illustrate a unibody stimulator electrode 2 with four dispersion pads. In this embodiment, the electrode 2 magnetically and electrically connects to the signal generator 212 without leadwires 3. Instead, the connection is achieved through magnets 206 that also provide electrical conductivity function. In different embodiments, the opening in the electrode 2 may be elliptical, round, square, or have other suitable shape to better conform the electrode to user’ s body or to avoid areas of the body not intended to receive the stimulation currents.

FIG. 4 illustrates a unibody stimulator electrode 2 with four dispersion pads. In some embodiments, the dispersion pads enable easier positioning of the electrode contacts at desired locations on user’s body. FIGS. 4A and 4B illustrate a unibody stimulator electrode 2 with four dispersion pads. In this embodiment the electrode 2 magnetically and electrically connects to the signal generator 212 through the magnets 206. In some embodiments, the dispersion pads enable easier positioning of the electrode 2 at desired locations on user’s body. FIG. 5 illustrates a circular unibody stimulator electrode 2 with four dispersion pads. In other embodiments, different shapes of the stimulator electrode 2 may be used. FIGS. 5A and 5B illustrate a unibody therapy electrode 2 with four dispersion pads. In this embodiment, the electrode 2 magnetically and electrically connects to the stimulator 200 through the magnets 206 that are also electrically conductive. In some embodiments, the dispersion pads enable easier positioning of the electrode 2 at desired locations on user’s body.

FIG. 6 illustrates a stimulator 200 in accordance with an embodiment of the present technology. The stimulator 200 is attached to the user’s submental area, but in different embodiments the stimulator may be attached or repositioned to different parts of the user’s body. In some embodiments, operation of the stimulator 200 may be controlled by wireless signals 42 (e.g., Bluetooth, Wi-Fi, etc.) of a wireless device 40 (e.g., smart phone, tablet, game console, etc.).

FIGS. 7A-7D are side views of a stimulator 200 in accordance with an embodiment of the present technology. The stimulator 200 may also be referred to as a “button” or “button stimulator.” Illustrated stimulator 200 includes a stimulator electrode 207 and a signal generator 212. These figures illustrate an embodiment without leadwires connecting the signal generator 212 to the stimulation electrode (also referred to as electrode body) 207. Instead, the signal generator 212 magnetically and electrically connects to the stimulator electrode 207. In operation, magnetic field 208 between magnets 206 and conductive elements 210 holds together the stimulator electrode 207 and the signal generator 212. The signal generator 212 may be detachable from the stimulator electrode 207. In addition to their magnetic function, the magnets 206 also conduct electrical current from the signal generator 212 to the stimulator electrode 207. Electrical current 209 is further transferred to skm 31 of user 30 by contacts 202. In operation, the stimulator 200 may be controlled by a wireless device 40.

FIGS. 7E-7F are side views of a stimulator 200 in accordance with an embodiment of the present technology. In particular, the illustrated embodiment may be referred to as the surface electromyography (sEMG) embodiment. Illustrated stimulator 200 includes the stimulator electrode assembly 207 and the signal generator 212. In operation, magnetic field 208 between magnets 206 and conductive elements 210 holds together the stimulator electrode 207 and the signal generator 212. The signal generator 212 is detachable from the stimulator electrode 207. In addition to their magnetic function, the magnets 206 also conduct electrical current from the signal generator 212 to the stimulator electrode 207 for the sEMG purposes. In operation, the stimulator 200 may be controlled by a wireless device 40 that also collects the sEMG data.

FIGS. 8A-8C are different views of a stimulator electrode 207 in accordance with an embodiment of the present technology. Stimulator substrate 204 carries magnets 206 on one side and contacts 202 on the opposite side. In some embodiments, the stimulator electrode 207 includes four contacts 202 that transfer two waveforms (two contacts per one waveform) to user’s skin. In some embodiments, contacts 202 may be made as a dispersive film, for example, as a combination of carbon dispersive film and hydrogel that is attachable to user’s skin.

FIGS. 9A-9C are different views of a signal generator 212 in accordance with an embodiment of the present technology. The signal generator 212 may be shaped as a button. In operation, the signal generator 212 generates target voltage/current waveforms and transfers the waveforms to the stimulator electrode 207 and further to user’s skin. The signal generator 212 may include an ON/OFF button 214. The signal generator includes a controller C (e.g., microprocessor, microcontroller, etc.) and a source of power 216 (e.g., batteries, rechargeable batteries, etc.). In operation, the controller C may apply duty cycle to the voltage/current waveforms, as explained below with reference to FIGS. 13-15.

FIGS. 9D-9G are different bottom views of the signal generator 212 which illustrate the assignment of each contact for purposes of surface electromyography (sEMG) measurements. sEMG may be understood as a process wherein microvolt levels of electrical activity involved in voluntary muscle contraction are sensed and then processed (i.e., amplification, filtering, and averaging) to provide a reliable measurement of the electrical activity. In one embodiment, the signal generator 212 and electrode assembly 207 are employed to record the electromyography measurements of the muscles below the electrode assembly 207. The controller C may assign an identification number or character for each contact point during the sEMG measurement process and may rotate the identification assignment of the contacts in either a clockwise or counterclockwise direction allowing a quadruple measurement to be obtained which is averaged to provide high reliability and definition of the sEMG measurements. In the illustrated context, “S” denotes “sensing” and “R” denotes “reference.” sEMG sensing may use the same signal generator (stimulation generator) 212 and electrode assembly 207 as is used during stimulation mode. The sEMG sensing occurs during the blanking period (i.e., during the sEMG window) of the stimulation therapy. While the stimulation is off, the sensing may remain active. In some embodiments, the processed sEMG signal triggers an involuntary stimulation of the targeted muscle. In this way, a patient/user can voluntarily contract the target muscle or muscles in order to cross a predetermined threshold and thereby trigger an involuntary and augmented muscle contraction. Such therapy may retrain or re-establish neural connections with damaged or atrophied muscles. The sEMG measurement can provide supportive information for patients who cannot visually see the results of their attempts to voluntarily activate the subject muscles. Additionally, the sEMG features may be used to measure performance improvements by the patient.

FIG. 10 is a graph of waveforms in accordance with an embodiment of the present technology. The horizontal axis represents time, and the vertical axis represents signal (voltage or current) strength. A square wave signal is illustrated, but other waveforms (e.g., a sinusoidal signal) may also apply. A first waveform 51 at frequency fl and a second waveform 52 at frequency f2 are illustrated as being offset on the timeline for convenience and clarity of presentation. However, in real applications the two waveforms are generated and applied simultaneously.

FIG. 11 is a graph of combined waveforms in accordance with an embodiment of the present technology. The horizontal axis represents time, and the vertical axis represents signal (voltage or current) strength. As explained above, the waveform 51 at frequency fl and the waveform 52 at frequency f2 may interact to combine at a heterodyne frequency f2-f 1 (also referred to as a beat frequency). As a non-limiting example, for fl of 4000 Hz and f2 of 4100 Hz, heterodyne frequency of waveform 53 is 4100 - 4000 = 100 Hz. Other combinations of frequencies are possible in different embodiments. Combining of frequencies may be referred to as heterodyning, mixing, intersecting, interfering, etc. The heterodyne waveform 53 exhibits itself at a heterodyne frequency inside the patient’s tissue.

FIG. 12 is a graph of waveforms in operation in accordance with an embodiment of the present technology. In the illustrated embodiment, the waveform 51 having frequency fl is applied over a pair of contacts 202-1, and the waveform 52 having frequency f2 is applied over a pair of contacts 202-2. As explained above, the waveforms 51, 52 interact and combine into a resulting waveform 53 at a heterodyne frequency. The hatched areas in the graph correspond to the heterodyne signal at the heterodyne frequency (beat frequency) f2 - fl. For example, when the heterodyne frequency is 100 Hz, its corresponding time period is 10 mS.

FIGS. 13 and 13A are graphs of waveforms with duty cycle in accordance with embodiments of the present technology. The horizontal axis indicates time, and the vertical axis indicates waveform intensity (voltage, current). The horizontal axis may be divided into two repeating periods of time: Atl during which the waveforms are applied to user’s skin, and At2 during which the waveforms are not applied to user’s skin. Such ON/OFF application of the waveforms 51, 52 may be achieved by a duty cycle generated by the controller C of the signal generator. The resulting waveforms that are applied during the periods of time Atl may be referred to as duty cycle interferential current stimulation (DCIFCS). The duty cycle may be defined as Atl\(Atl+ At2). In the illustrated embodiments, the Atl corresponds to 1 mS, and At2 corresponds to 4 mS, corresponding to a 20% duty cycle. Other values of duty cycle are also possible in different embodiments. A possible sEMG window is indicated in FIG. 13 A as having a 2-3 ms duration.

FIG. 14 is a graph of stages of neural response 60 in accordance with an embodiment of the present technology. The horizontal axis indicates time, and the vertical axis indicates neural response. As explained above, human neurons (also referred to as cell bodies, nerve cells, or motor neurons) have several phases of activation (de-polarization during the absolute refractory period) and deactivation (repolarization and hyperpolarization undershoot during the relative refractory period). When the neuron is not stimulated such neuron is at rest, therefore retaining its resting potential. When the neuron is first stimulated at time 0 (at the beginning of Atl), its action potential (e g., its nerve conducting potential) is triggered and starts travelling along the neural pathways. This phase is called a depolarizing phase, and it takes place during an absolute refractory period having a duration of Atl . In the next phase, the neuron’s action potential decreases during the re-polarization (at the beginning of At2) where the action potential of the neuron falls back toward its resting potential. Next, a certain amount of a variable undershoot occurs in the neuron during a hyper polarization undershoot, where the action potential of the neuron first falls below the resting potential and then rises back to the resting potential. Collectively, the re-polarization and hyper polarization phases of the neuron’s action potential are referred to as the relative refractory period having duration At2. For a neuron to again become sensitive to stimulation after the initial stimulus that triggers a depolarization phase, the neuron has to go through its re-polarization and hyper polarization phases during the relative refractory period. Therefore, during the relative refractory period the neuron is not sensitive to additional stimulation. In many situations, the absolute refractory period Atl is about 1 mS long, and the relative refractory period At2 is about 4 mS long.

FIG. 15 is a graph of timing of the electrical current waveforms in accordance with an embodiment of the present technology. The horizontal axis indicates time. The vertical axis indicates waveform strength (voltage, current) and neural response. The lower pair of graphs in FIG 15A shows neural response 60 and waveforms 503 corresponding to a continuous application of the voltage/current pulses. As explained with reference to FIG. 14 above, the target neurons are only sensitive to excitation current (e g., IFCS) during the absolute refractory period Atl, while remaining insensitive to the same current during the relative refractory period At2. Therefore, in many scenarios the expenditure of current/voltage during the relative refractory period At2 may be ineffective, while driving up overall current into the user’s body, which may be both undesirable from the patient’s point of view, as well as constitute an inefficient use of source power of the signal generator. In some embodiments, the absolute refractory period is about .25 to 1.75 mS, the relative refractory period is about 3.25 to 4.75 mS, and the duty cycle is about 5% to 37%.

The upper pair of graphs illustrates neural response 60 and waveforms 503 corresponding to a duty cycle application of the voltage/current pulses, resulting in the DCIFCS pulse packets. When selected to correspond to the absolute/relative refractory periods of the target neurons, the duty cycle applies the voltage/current waveforms 503 within the absolute refractory period Atl, while not applying the waveforms during the relative refractory period At2. In many embodiments, such application of the DCIFCS pulse packets within the absolute refractory period results in a more effective treatment by not exposing the patient to excessive current and/or not excessively draining the batteries of the signal generator.

In the illustrated scenario, the waveforms 503 are applied during the entire absolute refractory period. However, in different embodiments the waveforms 503 may be controlled by a duty cycle such that the waveforms are only applied during a part of the absolute refractory period, resulting in an ON phase of duty cycle IFCS that is shorter than the absolute refractory period, and an OFF phase of duty cycle that is longer than the absolute refractory period.

In many applications, the duration of application of the waveforms is not critical as long as the action potential is triggered (e.g., application of the waveforms may be shorter than the absolute refractory period). As a nonlimiting example, such partial application of the waveforms may be achieved by setting the ON part of the duty cycle to 0.5 mS and setting the OFF part of the duty cycle at 4.5 mS, resulting in a duty cycle of 10%.

In the context of this disclosure, words “about,” “generally” and “approximately” mean +/- 10% of the stated value or range. Many embodiments of the technology described above may take the form of computer- or controller-executable instructions, including routines executed by a programmable computer or controller. Those skilled in the relevant art will appreciate that the technology can be practiced on computer/controller systems other than those shown and described above. The technology can be embodied in a specialpurpose computer, controller or data processor that is specifically programmed, configured, or constructed to perform one or more of the computer-executable instructions described above. Accordingly, the terms "computer" and "controller" as generally used herein refer to any data processor and can include Internet appliances and hand-held devices (including palm-top computers, wearable computers, cellular or mobile phones, multi-processor systems, processor-based or programmable consumer electronics, network computers, minicomputers, and the like).

From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. Moreover, while various advantages and features associated with certain embodiments have been described above in the context of those embodiments, other embodiments may also exhibit such advantages and/or features, and not all embodiments need necessarily exhibit such advantages and/or features to fall within the scope of the technology. Accordingly, the disclosure can encompass other embodiments not expressly shown or described herein.

Claims

CLAIMS What is claimed is:

1. A system for electrical stimulation or therapy of a user, the system comprising: a first pair of contacts configured for contacting an area of user’ s skin; a second pair of contacts configured for contacting the area of user’s skin; and a generator of electrical voltage configured for providing a first waveform at a first frequency to the first pair of contacts and a second waveform at a second frequency to the second pair of contacts, wherein interactions of the first waveform and the second waveform generate a resulting waveform at a heterodyne frequency at the area of user’ s skin, wherein the resulting waveform is controlled as a duty cycle, and wherein a start of an ON phase of the duty cycle is synchronized with a start of an absolute refractory period of a target nerve, and a start of an OFF phase of the duty cycle is synchronized with a start of a relative refractory period of the target nerve.

2. The system of claim 1, wherein a duration of the ON phase of the duty cycle corresponds to the absolute refractory period of the target nerve, and a duration of the OFF phase of the duty cycle corresponds to the relative refractory period of the target nerve.

3. The system of claim 2, wherein the absolute refractory period is about 0.25 to 1.75 mS, the relative refractory period is about 3.25 to 4.75 mS, and the duty cycle is about 5% to 37%.

4. The system of claim 1, wherein the heterodyne frequency is a difference between the first frequency and the second frequency.

5. The system of claim 4, wherein the first frequency is 1,000 Hz to 20,000 Hz, and the second frequency is 1,000 Hz to 20,000 Hz.

6. The system of claim 1, wherein the first pair of contacts and the second pair of contacts are carried by a stimulator electrode that is magnetically and electrically coupled with a signal generator.

7. The system of claim 6, wherein the first waveform and the second waveform are transmitted through magnets of the stimulator electrode to the area of user’s skin.

8. The system of claim 6, wherein the first pair of contact and the second pair of contacts comprise a dispersive film configured for contacting the area of user’s skin.

9. The system of claim 6, wherein the signal generator is detachable from the stimulator electrode.

10. The system of claim 6, wherein the signal generator is configured for wireless communication with a mobile device.

11. A method for electrical stimulation or therapy of a user, the method comprising: generating a first waveform at a first frequency by a generator of electrical voltage; generating a second waveform at a second frequency by the generator of electrical voltage; transmitting the first waveform to a first pair of contacts configured for contacting an area of user’s skin; transmitting the second waveform to a second pair of contacts configured for contacting the area of user’ s skin, wherein interactions of the first waveform and the second waveform generate a resulting waveform at a heterodyne frequency at the area of user’ s skin; and controlling the resulting waveform as a duty cycle, wherein a start of an ON phase of the duty cycle is synchronized with a start of an absolute refractory period of a target nerve, and a start of an OFF phase of the duty cycle is synchronized with a start of a relative refractory period of the target nerve.

12. The method of claim 11, wherein a duration of the ON phase of the duty cycle corresponds to the absolute refractory period of the target nerve, and a duration of the OFF phase of the duty cycle corresponds to the relative refractory period of the target nerve.

13. The method of claim 11, wherein a duration of the ON phase of the duty cycle is equal or shorter than a duration of the absolute refractory period of the target nerve, and a duration of the OFF phase of the duty cycle is equal or longer than the relative refractory period of the target nerve.

14. The method of claim 11 , wherein the absolute refractory period is about 0.25 to 1.75 mS, and the relative refractory period is about 3.25 to 4.75 mS.

15. The method of claim 14, wherein the duty cycle is 5% to 37%.

16. The method of claim 11, wherein the heterodyne frequency is difference between the first frequency and the second frequency.

17. The method of claim 11, wherein the first frequency is 1,000 Hz to 20,000 Hz, and the second frequency is 1,000 Hz to 20,000 Hz.

18. The method of claim 11 , wherein the first pair of contact and the second pair of contacts are carried by a stimulator electrode, the method further comprising magnetically and electrically coupling the stimulator electrode with a signal generator.

19. The method of claim 18, wherein the first waveform and the second waveform are transmitted through magnets of the stimulator electrode to the area of user’s skin.

20. The method of claim 11, wherein a signal generator is detachable from a stimulator electrode.

21. The method of claim 11, further comprising wirelessly providing instructions to the signal generator by a mobile device.