A scalable, non-invasive, high-frequency stimulator for tactile sensory feedback

Abstract

A scalable, high-density, electrical stimulator to provide haptic feedback. The system and method are designed for low-voltage, high-frequency TENS-based sensory / haptic feedback. The stimulator permits more than one electrode to be connected to each of the stimulator channels through a scalable electrode switch board. The stimulator may be used for, for example, enervating prosthetics, virtual reality applications, and augmented reality applications.

Description

A SCALABLE, NON-INVASIVE, HIGH-FREQUENCY STIMULATOR FOR TACTILESENSORY FEEDBACKCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Ser. No. 63 / 655,671, filed June 4, 2024, the disclosure of which is incorporated herein by reference.GOVERNMENT FUNDING

[0002] This invention was made with government support under grant W81XWH-20- 1-0842 awarded by the Department of Defense. The government has certain rights in the invention.FIELD

[0003] This disclosure relates generally to providing haptic feedback, and more specifically to a wearable neurostimulator.BACKGROUND

[0004] Tactile sensory feedback based on transcutaneous electrical nerve stimulation (TENS) has significantly advanced the provision of haptic feedback through neurostimulation. Prosthetic technology for amputees, and virtual reality / augmented reality (VR / AR) devices have been improved in that object manipulation and the restoration of critical tactile sensations such as touch and grasp have been enabled. In contrast to mechanical actuators, which deform the skin using external forces to provide tactile feedback, TENS achieves sensory feedback by delivering currents directly to the peripheral sensory neurons through electrodes placed on the skin above the amputation. In the case of amputees, the axons of these neurons were once connected to mechanoreceptors in the now amputated limbs. Tactile sensations, perception of roughness or softness, may be reproduced when neurons are stimulated by TENS. TENS-based sensory feedback or electro-tactile devices are lightweight with high spatial resolution and miniaturized form. However, the development of wearable TENS-based devices has been hindered by challenges such as the requirement for high voltages. This is due to the considerable skin impedance encountered at low frequenciesof conventional TENS (< 1000 Hz), where skin impedance may exceed 100 khoums, necessitating voltages over 100 V to deliver 1 mA of current to the skin. Additionally, the need for larger electrodes to decrease skin / electrode impedance precludes the possibility of high density stimulation which may evoke more nuanced and naturalistic sensory experiences. Such stimulation may for example enhance the usability of prosthetic devices and, by extension, the quality of life for amputees. Recent studies indicate that operating at higher frequencies may potentially reduce skin impedance due to the inverse relationship between skin impedance and frequency. This allows smaller electrodes for high-density stimulation, and lower voltage required to deliver the same level of current. The solutions to this problem are not only relevant for prosthetic feedback, but are also immediately applicable to other applications of haptic feedback, such as, but not limited to, VR / AR. What is needed is a device that combines low voltage, high frequency, and multiple electrodes to enable high-density stimulation.SUMMARY

[0005] The system and method of the present disclosure includes a scalable, high- density, electrical stimulator to provide haptic feedback. The system and method are designed for low-voltage, high-frequency TENS-based sensory / haptic feedback. The stimulator permits more than one electrode to be connected to each of the stimulator channels through a scalable electrode switch board. The stimulator may be used for, for example, enhancing prosthetics, virtual reality applications, and augmented reality applications.

[0006] A system of one or more computers may be configured to perform particular operations or actions by virtue of having software, firmware, hardware, or a combination of them installed on the system that in operation causes or cause the system to perform the actions. One or more computer programs may be configured to perform particular operations or actions by virtue of including instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions. One general aspect includes a method for delivering high density electrical signals by a device, where the device includes a controller, an electrical signal source, an electrode array, a switch array, and a power supply. The method includes providing power, by the power supply, to the controller, the electrical signal source, and the switch array. The method also includes providing, by the controller, a first command to the electrical signal source. The method also includes sending, by theelectrical signal source, in response to the first command, electrical signals to a switch array. The method also includes providing, by the controller, a second command to the switch array. The method also includes sending, by the switch array, in response to the second command, electrical signals to a pre-selected set of electrodes in the electrode array at a frequency of 1kHz or more. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0007] Implementations may include one or more of the following features. The device may include a VR / AR system. The method may further include receiving, by the controller, a selection of a device mode. The device mode may include a first mode and a second mode. The electrical signal source provides at a frequency of 10kHz or more a constant voltage when the device is in the first mode, and the electrical signal source provides at a frequency of 10kHz or more a constant current when the device is in the second mode. The device may include a stimulator, and the method may include delivering, by the stimulator, transcutaneous signals through the electrodes to a user. The method may include activating the electrodes using one or more channels to provide stimulation at varying positions. The device may include a wearable device. The electrodes form a scalable electrode array. The power supply may include a battery. The electrodes and a spacing between the electrodes may include < 8mm. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.

[0008] One general aspect includes a device for delivering high density electrical signals. The device includes a controller. The device also includes an electrical signal source electronically coupled with the controller. The device also includes a switch array electronically coupled with the electrical signal source. The device also includes an electrode array electronically coupled with the switch array. The device also includes a power supply powering the controller, the electrical signal source, and the switch array. The controller executes instructions enabling operations including providing power, by the power supply, to the controller, the electrical signal source, and the switch array, and providing, by the controller, a first command to the electrical signal source. The operations include sending, by the electrical signal source, in response to the first command, electrical signals to a switch array, providing, by the controller, a second command to the switch array, and sending, bythe switch array, in response to the second command, signals to a pre-selected set of one or more electrodes in the electrode array at a frequency of 1kHz or more. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0009] Implementations may include one or more of the following features. The device where the operations further may include receiving, by the controller, a selection of a device mode, the device mode including a first mode and a second mode, where the electrical signal source provides a constant voltage when the device is in the first mode, and where the electrical signal source provides a constant current at a frequency of 10kHz or more when the device is in the second mode. The operations further may include adjusting the constant voltage to provide a pre-selected current into and out of the electrodes. The device delivers bi-phasic square waves transcutaneously, the bi-phasic square waves reduce an impedance of a delivery surface, the reduced impedance is measured by the controller, and the controller lowers the constant voltage based on the reduced impedance. The operations further include measuring, by the ADC, a voltage across a resister in the current sensor, reading, by the controller, the ADC to measure a current, adjusting, by the controller, the voltage at the digital-to-analog converter (DAC) to achieve a pre-selected current when the device is in the second mode. The operations include sending, by the controller, signals to the switch board, and connecting and latching, by the controller using a multiplexer, one or more channels to the one or more electrodes, the one or more electrodes electronically coupled with the switch board. The electrode array is scalable. The device may include a wearable stimulator. The power supply may include a battery. The operations further may include choosing one or more electrodes arbitrarily from the electrode array for connection to one or more channels. The operations further may include activating the electrodes to provide stimulation at varying locations using one or more channels. The voltage module and the current module are electronically coupled with the controller. A maximum output voltage may include 32V. The device may include closed loop control to monitor current passing through the electrodes. The switch array may include high voltage analog switches with low resistance. The power supply may include a 3.7V battery. The stimulator provides signals to one or more of nerves, touch receptors, or muscles. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.

[0010] One general aspect includes a computer-readable medium storing instructions for delivering high density electrical signals by a device. The instructions include providing power, by the power supply, to the controller, the electrical signal source, and the switch array. The instructions also include providing, by the controller, a first command to the electrical signal source. The instructions also include sending, by the electrical signal source, in response to the first command, electrical signals to a switch array. The instructions also include providing, by the controller, a second command to the switch array. The instructions also include sending, by the switch array, in response to the second command, signals to a pre-selected set of electrodes in the electrode array at a frequency of 1kHz or more. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and / or other aspects and advantages will become more apparent and more readily appreciated from the following detailed description of examples, taken in conjunction with the accompanying drawings, in which:

[0012] FIG. 1 A is a schematic block diagram of a stimulator system in accordance with embodiments of the present disclosure;

[0013] FIG. IB is a perspective diagram of the electronics of a simulator in accordance with embodiments of the present disclosure, and a schematic block diagram of the simulator in accordance with embodiments of the present disclosure;

[0014] FIG. 2A is a schematic block diagram of a scalable switch board in accordance with embodiments of the present disclosure;

[0015] FIG. 2B is a circuit diagram of a scalable switch board of FIG. 2A, in accordance with embodiments of the present disclosure;

[0016] FIG. 3 A is a graphical representation of impedance versus frequency when using an electrical model of skin;

[0017] FIG. 3B is an electrical model of skin (RC circuit);

[0018] FIGs. 4A and 4B are graphical representations of the functionality of current and voltage control mode;

[0019] FIG. 4C is a skin model circuit used to provide the results presented in FIGs.4 A and 4B;

[0020] FIGs. 5A-5C are graphical illustrations of the programmability of the stimulator;

[0021] FIGs. 6A-6E are graphical representations of the results of arbitrary electrode connection verification;

[0022] FIG. 7 is a table of parameters for a stimulator in accordance with embodiments of the present disclosure;

[0023] FIG. 8 is a pictorial representation of a stimulator in use with a prosthetic limb in accordance with embodiments of the present disclosure;

[0024] FIG. 9 is a pictorial representation of a stimulator in use with a VR / AR system in accordance with embodiments of the present disclosure; and

[0025] FIG. 10 is a flowchart of a method for stimulating tissue in accordance with embodiments of the present disclosure.DETAILED DESCRIPTION

[0026] In order for the present disclosure to be more readily understood, certain terms are first defined below. Additional definitions for the following terms and other terms may be set forth throughout the specification. If a definition of a term set forth below is inconsistent with a definition in an application or patent that is incorporated by reference, the definition set forth in this application should be used to understand the meaning of the term.

[0027] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to “a method” includes one or more methods, and / or steps of the type described herein and / or which will become apparent to those persons skilled in the art upon reading this disclosure and so forth.

[0028] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Further, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In describing and claiming the methods, systems, and computer readable media, the followingterminology, and grammatical variants thereof, will be used in accordance with the definitions set forth below.

[0029] Referring now to FIG. 1 A, shown is a schematic block diagram of a device in accordance with embodiments of the present disclosure. The controller 105 may control programmable stimulation waveforms to an array 116 of electrodes through a switch array 115. In some configurations, the switch board 115 is used to achieve arbitrary electrode connections. In some configurations, the switch board 115 has sixteen outputs which are connected to sixteen electrodes on a 4-by-4 electrode array 116. In some configurations, the electrode array 116 is based on a flexible printed circuit board (FPCB) design. In some configurations, the electrodes are placed in 2-by-8 or 4-by-4 configuration, for example. In some configurations, the electrode array 116 has copper pads as electrode nodes. In some configurations, the electrode pad diameter is 3mm, and the center-to-center distance between the adjacent pads is twice the diameter. In some configurations, cutouts are added between two adjacent electrode pads to improve the flexibility as the cutouts allow the electrode array to bend and twist. The flexible electrode array 116 may be directly attached to the skin. Another option is to solder silver paste such as, for example, but not limited to, AA-DUCT ADI from Atom Adhesives, on the pads. The silver paste tends to form a semi -sphere on the pad and is biocompatible.

[0030] In some configurations, control of the device is provided by a processor such as, for example, but not limited to, a controller 105 such as a microcontroller. The processor assigns the pins of the controller 105 for control and interface signals such as, for example, serial peripheral interface (SPI) communication. The processor executes instructions to carry out operations such as, for example, but not limited to, setting up parameters, such as, for example, but not limited to, the amplitude and frequency of the waves. Values for these parameters may be provided by, for example, but not limited to, user input and / or the result of a computation such as, for example, the execution of a MATLAB® script. In some configurations, the processor may include instructions to execute a live script. Interactive controls may determine the values of the parameters such as amplitude and frequency. In some configurations, the processor may include instructions to perform operations such as providing the parameters in a string message that may be transferred, for example, by serial communications links. The parameters may be modified in real-time to optimize the parameter values with respect to each other, for example.

[0031] A method in accordance with embodiments of the present disclosure includes sending, by the controller 105, commands to store voltages on channels 209 (FIG. 2 A) and simultaneously updating the channels 209 (FIG. 2A) to new values. The method includes setting, by the controller 105, the mode of the device, either voltage control or current control. If the device is in voltage control mode, the method includes sending, a target voltage by sending a command to the DAC, which sends an output voltage that is proportional to the target voltage to the non-inverting amplifier circuit. Selection of the connection to the noninverting amplifier circuit is made by an analog switch. If the device is in current control mode, the method includes sending, a target current by sending a command to the DAC, which sends an output voltage that is proportional to the desired current to the improved Howland current pump circuit. Selection of the connection to the Howland current pump circuit is made by an analog switch. The method includes measuring a voltage across a resister in the current sensing circuit. If current control is being used, the method includes using, by the controller 105, the current measurement to adjust the voltages to achieve a set current. The method includes sending, by the controller 105, the outputs to a switch board 115. The method includes connecting and latching, by the controller 105, the channels 209 (FIG. 2 A) to any of the electrodes in the switch board 115. Referring now to FIG. IB, shown are a photograph of a circuit board configuration of a stimulator in accordance with embodiments of the present disclosure, and a schematic block diagram of the stimulator . In some configurations, the stimulator includes three printed circuit boards (PCBs): a regulator board, a channel board, and a switch board. In some configurations, the stimulator 100 has a voltage control mode and a current control mode. The current control circuit 111 automatically adjusts its voltage to ensure a constant current is flowing into / out of the electrodes.

[0032] In some configurations, the regulator board includes a voltage regulation module 101 and a 3.7 V battery 103 to power the device. The operational voltage values vary from component to component. The voltage regulation module 101 boosts the 3.7 V provided by the battery 103 to the different voltage values that supply power to the device. In alternate configurations, the regulator board includes a voltage regulator, two boost converters, and a low dropout (LDO) regulator. In some configurations, the voltage regulator is the ADP5070 from Analog Devices. In some configurations, the voltage regulator is a DC-to-DC switching regulator with independent positive and negative output. Depending on the peripheralnetwork components used, ± 15 V may be generated by the voltage regulator. In some configurations, the boost converter is a LT8365 from Analog Devices. In some configurations, the boost converter generates ± 34 V. In some configurations, the LDO regulator is the AZ1117IH-5.0TRG1. In some configurations, the LDO regulator divides a 5 V output from the + 15 V load to power, for example, a controller.

[0033] In some configurations, the channel board includes a micro-controller unit (MCU) 105, a digital -to-analog converter (DAC) 107, a voltage control module 109 based on, for example, but not limited to, non-inverting amplifier (NIA), a current control module 111 based on, for example, but not limited to, a Howland current pump (HCP) 111 and a current sensing module (CS) 113. In some configurations, the MCU 105 is the TEENSY® 4.0 from PJRC. The MCU 105 initiates the DAC 107 to generate voltage waves and receives voltage sensing values from analog-to-digital converters (ADCs) (not shown) that are part of the CS 113. The MCU 105 also provides control signals and addressing pins for other modules. The MCU 105 may control programmable stimulation waveforms to an array of electrodes 127 by controlling two stimulating channels 209 (FIG. 2A).

[0034] A method in accordance with embodiments of the present disclosure includes sending, by the controller 105, commands by, for example, but not limited to, an SPI to the DAC 107 to store two voltages on channels 209 (FIG. 2A). The method includes sending, by the controller 105, a message to the DAC 107 to simultaneously update both channels 209 (FIG. 2 A) to a new value. The method includes setting, by the controller 105, the mode of the device, either voltage control or current control. If the device is in voltage control mode, the method includes sending, by the DAC 107, an output to the voltage module 109, and sending, by the voltage module 109, an output to the CS circuit 113. If the device is in current control mode, the method includes sending, by the DAC 107, an output to the current module 111, and sending, by the current module 111, an output to the current sensing circuit 113. The method includes measuring, by an ADC, a voltage across a resister in the CS circuit. The method includes reading, by the controller 105, the ADC through, for example, but not limited to, an SPI. If current control is being used, the method includes using, by the controller 105, the current measurement to adjust the voltages at the DAC 107 to achieve a set current. The method includes sending, by the controller 105, the outputs to a switch board 115. The method includes using, by the controller 105, a multiplexer 201 (FIG. 2A) toconnect and latch the stimulating channels 209 (FIG. 2A) to any of the electrodes 127 in the switch board 115.

[0035] In some configurations, the DAC 107 is the MAX5322EAI+ from Analog Devices which is a 12-bit, dual DAC. In some configurations, the DAC 107 is a two-channel DAC. In some configurations, the DAC 107 supports high speed (up to 10 MHz) communication via SPI. The two output channels of the DAC 107 are programmed to generate two square wave pulses 119 that are “off-phase”. Thus, when one channel serves as the current source 104, the other may serve as the sink.

[0036] In some configurations, the voltage module 109 includes two non-inverting amplifiers. In some configurations, the operational amplifier is the OPA455 by Texas Instruments, Inc. In some configurations, the voltage module 109 includes a high-voltage, high-current drive type, making it suitable for the voltage control and the current control discussed herein. The current module 111 includes a device based on, for example, but not limited to, the HCP. In some configurations, the current module 111 includes an operational amplifier and a balanced resistor bridge. The current module 111 may maintain constant current flow when applying DC voltage as the input. The value of the output current is determined by the input voltage and the resistance of a factor resistor. In some configurations, the current pump supports dual signals input. In the current module 111, the outputs of the DAC 107 are directly applied as the inputs to the current pump. The output current signals are also dual and “in-phase” with the inputs. Analog switches are placed before and after the voltage module 109 or the current module 111, controlled by the MCU 105 to achieve mode selection. The stimulator 100 selects its state as either voltage mode or current mode depending on the desired mode and by configuring an analog switch at the output of the DAC. The stimulator 100 may control the voltage amplitude between its channels 209 (FIG. 2A) when the stimulator 100 is set at voltage control mode. The voltage amplitude value is settable. In addition to controlling the amplitude and frequency, the stimulator 100 may generate different waveform shapes that are commonly used for nerve stimulation applications.

[0037] In some configurations, the CS module 113 has one current sensing resistor for each channel to monitor the current flowing into the body. The voltage across the sensing resistor is followed by a differential amplifier and sent to an ADC. The ADC converts the analog voltage value into digital bits. These bits are fed back to the MCU 105 whichcalculates the current going through the electrodes by measuring the voltage across the series current sensing resister. The real-time current value after the calculation may be displayed along with the bits. In some configurations, the ADC used is the MAXI 1156 from Analog Devices. In some configurations, the ADC is an 18-bit, ± 5 V ADC that supports SPI communications. The ADC may support an absolute voltage value as its input. When the ADC is not used to measure the voltage difference across the current sensing resistor directly, a differential amplifier measures the voltage difference. In some configurations, the differential amplifier is the INA149 from Texas Instruments.

[0038] Referring now to FIG. 2A, the switch board 115 enables various combinations of connections between the channels 209 and the electrodes 127 of the electrode array 116 (FIG. 1 A). The latching analog switch 206 determines whether an electrode 127 is connected to a specific channel 209 at any given time. When the latching analog switch 206 is closed, a channel 209 is connected to an electrode 127. In some configurations, other components are connected to electrodes 127 by the switch board 115, for example, but not limited to, electrodes that enable haptic feedback. In some configurations, the switch board 115 may connect channels to components other than electrodes 127. In some configurations, the latching analog switches 206 share the same control signal line. Multiplexers may be applied to assign the control signal to an individual latching analog switch 206 using, for example, binary addressing. For example, four digital pins are adequate for addressing sixteen electrodes 127. In some configurations, an additional pin is applied when the switch array 115 has two channels. In the switch array 115, there are n control lines 202, and 2nelectrodes 127, making this configuration scalable. Further, the channels 209 may be connected to multiple electrodes 127 simultaneously. In some configurations, once set, the DL remains latched and may connect multiple electrodes.

[0039] Referring now to FIG. 2B, in some configurations, the switch board 115 includes multiplexers (MUXs) 201, D-latches (DL) 203 and analog switches 205 A, which enable connection between the stimulator channels 209 and any combination of electrodes 127. The structure of the analog switch 205A is highlighted by the frame 205. The lines 207 are the E control and D control for D-latch 203 inputs. The switch board 115 enables free connection between the two channels 209 and the sixteen electrodes 127 of the electrode array. The analog switch 205A determines whether the electrode 127 is connected to a specific channel 209 at any given time. When the analog switch 205A is closed, a channel209 is connected to an electrode 127 and will remain connected until the DL is updated. In some configurations, other components are connected to electrodes 127 by the switch board 115. In some configurations, the switch board 115 is used for a purpose other than enabling haptic feedback. In some configurations, the switch board 115 may connect channels to components other than electrodes 127. In some configurations, the analog switch is the MAX14757 from Maxim Integrated. In some configurations, the analog switch 205A is a quad single-pole single-throw (SPST) analog switch in which four switch units are integrated in one chip package. In some configurations, the analog switches 127 share the same control signal line. In some configurations, the multiplexers 201 are CD74HC4067 and SN74LVC1G3157 from Texas Instruments. A first multiplexer 201 is a 16-by-l type that attributes control signals to the analog switches 127. A second type of multiplexer 201 is a 2- by-1 type that selects between channels 209. In some configurations, the DL 203 is a SN74LVC1G373 from Texas Instruments. The DL 203 locks the state of the analog switch 205A when the control signal is shifted to another analog switch 205A.

[0040] Referring now to FIGs. 3 A and 3B, with respect to skin impedance and frequency, a skin model is used to determine whether a high-frequency stimulation causes the skin impedance to drop. The skin model includes a resistor / capacitor (RC) circuit 300 (FIG. 3B) - a 510 kOhm resistor 301 (FIG. 3B) in parallel with a 47 nF capacitor 303 (FIG. 3B) . A square wave of the frequency range of 10 Hz -10 kHz is used to stimulate the skin model. FIG. 3 A shows a graph of the skin model impedance with frequency increasing from 10 Hz to 10 kHz. In some configurations, the skin model impedance is around 520 kOhm when the square wave frequency is relatively low because the capacitor has a large impedance at low frequencies. The capacitor branch may be considered an open circuit. Thus, the impedance of the RC skin model 300 (FIG. 3B) is close to Rs. For high frequency situations, the impedance of the capacitor drops dramatically, making the branch act like a short circuit to block the parallel resistor Rs. The skin model impedance decreases when applying a high frequency signal to the skin model 300 (FIG. 3B). With lower skin impedance, a lower and safer voltage value is enough to deliver the same level of current for stimulation. The stimulator 100 (FIG. 1 A) may switch between two different modes to either provide constant current or voltage control.

[0041] Referring now to FIGs. 4A-4C, to verify that either voltage or current control achieves the desired functionality of the voltage control module 109 (FIG. 1A), a 10 kOhm401 (FIG. 4C) potentiometer is placed in series to modify the impedance of the circuit for the skin model 300 (FIG. 3B), forming circuit 400 (FIG. 4C). As the voltage control module 109 (FIG. 1 A) executes, the stimulator 100 (FIG. 1 A) is switched to voltage mode, the voltage output amplitude is set at 10 V, and the potentiometer 401 modifies the load with three different impedance levels: 0, 50, and 100%. Voltage across the current sensing resistor is recorded to monitor the current change. The voltage difference between the channels 209 (FIG. 2B) is recorded. Similarly, as the current module executes, the stimulator 100 (FIG.1 A) is set at current mode to produce 1 mA, the current sensing resistor and the potentiometer 401 are 1 kOhm types, the impedance modification and responses measurements are conducted, and the responses are recorded for the current mode. The signal frequency is fixed at 10 kHz for both voltage and current modes. FIG. 4A shows the voltage difference between the channels and the current flow through the circuit 400 (FIG. 4C);The subplots in the upper row show the voltage difference between channels. The subplots in the bottom row show the current. “Low” load means the potentiometer 401 (FIG. 4C) is short-circuited from the circuit. “Medium” load means half the potentiometer 401 (FIG. 4C) is connected. “High” load means the whole potentiometer 401 (FIG. 4C) is connected into the circuit 400 (FIG. 4C). As shown in FIG. 4 A, the current amplitude is maintained at 1 mA no matter how the load impedance changes. The current value is equal to a pre-set value. The voltage between the channels 20 (FIG. 4C) has a fluctuating amplitude which has the same trend as the impedance. The potentiometer 401 (FIG. 4C) gives 0, 0.5 and 1 kOhm of resistance to the circuit 400 (FIG. 4C). As the RC skin model has little impedance for high frequency situation, the total impedance of the circuit 400 (FIG. 4C) changes as 1, 1.5 and 2 kOhm. The current is maintained at 1 mA. The voltage values are expected to be 1, 1.5 and 2 V. As shown in the graph in FIG. 4A, the voltage amplitude is similar to expected values though slight distortion from a standard square wave may be observed in the voltage responses due to the capacitive component in the circuit 400 (FIG. 4C). Thus, the stimulator 100 (FIG. 1 A) may maintain the current amplitude in current control mode. For the voltage control mode, the voltage difference between the channels 209 has a constant amplitude of 20 V given different load impedance. With a constant voltage difference between the channels 209 (FIG. 4C), the current amplitude decreases when larger load impedance is added to the circuit 400 (FIG. 4C). For each load, the total impedance is 10, 15 and 20 kOhm. The expected currentvalue is 2, 1.3 and 1 mA, and the results shown in the graphs in FIG. 4B concur with the expected results.

[0042] Shown in FIG. 4B are the responses recorded for the voltage mode. The value of Rs and Cs are the same for both modes (Rs = 510 kOhm, Cs = 47 nF). The value of Rc and the potentiometer resistance are different. For current mode, Rc = R_potentiometer = 1 kOhm. For voltage mode, they are replaced by Rc = R_potentiometer = 10 kOhm.

[0043] Referring now to FIGs. 5 A-5C, the programmability of the types of waveforms of the stimulator 100 (FIG. 1 A) is shown - FIG. 5A shows a sine wave, FIG. 5B shows a triangle wave, and FIG. 5C shows an amplitude modulation. For amplitude modulation, the message signal is a 10 kHz square wave, and the carrier signal is the 100 Hz sine wave. The shown waveforms have the same amplitude of 15 V. The stimulator 100 (FIG. 1 A) is programmable to produce not only square waveforms, but multiple other waveforms. For instance, sine wave and triangle wave are two commonly used waveforms for stimulation. The analog switch 205 A (FIG. 2B) may select arbitrary electrodes 127 (FIG. 2B) to connect to stimulator channels 209 so that different stimulation patterns are formed for richer sensory feedback production.

[0044] Referring now to FIGs. 6A-6E, to illustrate how the switch board works, the results from the selection of arbitrary electrodes 127 (FIG. 2B) connected to stimulator channels 209 (FIG. 2B) are shown. The selected electrodes 127 (FIG. 2B) of the electrode array form different stimulation patterns, which are used to evoke various sensations. In some configurations, the stimulator 100 (FIG. 1A) passes through four states. When different electrodes 127 (FIG. 2B) are selected to connect with the stimulator channels 209 (FIG. 2B) for each individual state, four different patterns cross (FIG. 6B), letter “H” (FIG. 6D), “J” (FIG. 6C) and “U” (FIG. 6E) are formed. The signals of the sixteen electrodes 127 (FIG. 2B) are recorded. The patterns are visualized through use of an electrode array heatmap and bar graph. FIG. 6A shows the signals recorded from the sixteen electrodes 127 (FIG. 2B). The subplot of each electrode 127 (FIG. 2B) is arranged according to its position in the electrode array. Line 601 (FIG. 6A) shows the voltage signals. A voltage of + 5 V means the electrode 127 (FIG. 2B) is connected to a first channel 209 (FIG. 2B). A voltage of -5 V means the electrode 127 (FIG. 2B) connected to a second channel 209 (FIG. 2B). When the voltage is + 5 V, different patterns (states) are shown by different patterns to enable discrimination between the different states, each of which has a specific time spot 603 (FIG. 6A). Theelectrode array heatmaps for the four states are shown in FIGs. 6B-6E. The electrode array heatmap of a first state is shown in FIG. 6B, the electrode array heatmap of a second state is shown in FIG. 6C, the electrode array heatmap of a third state is shown in FIG. 6D, and the electrode array heatmap of a fourth state is shown in FIG. 6E. In the diagrams, the pattern maps for the heatmap are customized to represent a highest value (patterned) and a lowest value (non-pattemed). In FIG. 6B, electrodes 2, 5, 6, 7 and 10 are connected to the + 5 V channel. The other eleven electrodes are connected to the - 5 V channel. These signals are recorded and displayed as lines 601 (FIG. 6A). In FIG. 6B, for the electrode connected to + 5 V, patterned bar graphs are plotted. A cross pattern is visible when focusing on the patterned block. In FIG. 6C, electrodes 1, 2, 3, 4, 7, 9, 11, 13, 14 and 15 are connected to + 5 V and the other six electrodes are connected to - 5 V. The patterned bar graph of FIG. 6 A and the heatmap in FIG. 6C both exhibit the letter “J” pattern. In FIG. 6D, electrodes 1, 4, 5, 6, 7, 8, 9, 12, 13 and 16 are connected to + 5 V. The letter “H” pattern is displayed in bar graphs and a heatmap. In FIG. 6E, electrodes 1, 4, 5, 8, 9, 12, 13-16 are selected to connect to + 5 V for a pattern of letter “U”. More complex patterns to advance richer sensation production are achievable by varying the connections or density of the electrode array.

[0045] Referring now to FIG. 7, a table of values indicates parameters for a stimulator configuration. Other parameters may be used to characterize the stimulator 100 (FIG. 1 A) such as, for example, but not limited to, power consumption, maximum output voltage / current range, and resolution. As shown in the table, the maximum frequency is up to 50 kHz and the maximum output voltage amplitude is 32 V. In some configurations, the stimulator 100 (FIG. 1A) controls the current and voltage with resolutions of 3.2 mV and 0.0032 mA (current mode). In some configurations, in current mode, the maximum output current amplitude is 6.6 mA. In some configurations, this parameter is larger for voltage mode because the maximum current for the operational amplifier is 45 mA. An overcurrent protection may be added with the threshold of, for example, but not limited to 10 mA. In some configurations, when current amplitude is higher than this threshold, the stimulator 100 (FIG. 1 A) shuts down which may be accomplished by, for example, but not limited to, setting the voltage value to zero for both channels 209 (FIG. 2B). The analog switch 205 A (FIG. 2B) performance may be evaluated by the switch speed and cross talk. In some configurations, the delay between two switch activities is 0.5 ms. The cross talk between adjacent electrodes is 2.8%, indicating little signal interface exists between adjacent electrodetraces. In some configurations, the input voltage range is 3-4 V as the stimulator 100 (FIG. 1A) is supplied by a 3.7 V battery 103 (FIG. 1 A). In some configurations, voltage input lower than 3 V is too low for the voltage regulation module to generate enough voltage to supply the components.

[0046] Referring now to FIG. 8, shown is a pictorial representation of a device 100 in accordance with the present disclosure. In this illustration, the device 800 is a stimulator that is creating signals based on tactile sensor readings. The signals from the prosthesis sensor are received by the stimulator 800 and sent to the brain. The high-density electrode array 801 electrically stimulates residual nerves to elicit tactile sensations in the phantom limb.

[0047] Referring now to FIG. 9, shown is a stimulator 909 in accordance with embodiments of the present disclosure that provides haptic feedback to a user in virtual or augmented reality (VR or AR). The stimulator 909 is embodied as a wearable armband that may electrically stimulate the tactile sensory nerves 903 in the arm. As shown in the drawing, a user interacts with a virtual object 907 such as an apple using touch receptors 901 in the hand (in AR or VR). The wearable neural stimulator 909 is commanded by an AR / VR system to electrically stimulate the nerves 903 in the arm with a specific pattern to elicit a tactile sensation 905. The user experiences the tactile sensation 905 of the virtual object 907 in the touch receptors 901 in the hand.

[0048] Referring now to FIG. 10, a method in accordance with embodiments of the present disclosure delivers high density electrical signals by a device. The device includes, but is not limited to including, a controller, an electrical signal source, one or more electrodes, a switch array, and a power supply. The method includes providing 1002 power, by the power supply, to the controller, the electrical signal source, and the switch array. The method includes providing 1004, by the controller, a first command to the electrical signal source, and sending 1006, by the electrical signal source, in response to the first command, electrical signals to a switch array. The method includes providing 1008, by the controller, a second command to the switch array, and sending 1010, by the switch array, in response to the second command, signals to a pre-selected set of electrodes in the electrode array at a frequency of IkHZ or more.

[0049] While the invention has been described with reference to the exemplary embodiments thereof, those skilled in the art will be able to make various modifications to the described embodiments without departing from the true spirit and scope. The terms anddescriptions used herein are set forth by way of illustration only and are not meant as limitations. In particular, although the method has been described by examples, some steps of the method may be performed in a different order than illustrated or simultaneously. Those skilled in the art will recognize that these and other variations are possible within the spirit and scope as defined in the following claims and their equivalents. All patents, patent applications, other publications or documents, and the like cited herein are incorporated by reference in their entirety for all purposes to the same extent as if each individual item were specifically and individually indicated to be so incorporated by reference.

Claims

CLAIMS1. A method for delivering high density electrical signals by a device, the device including a controller, an electrical signal source, an electrode array, a switch array, and a power supply, the method comprising: providing power, by the power supply, to the controller, the electrical signal source, and the switch array; providing, by the controller, a first command to the electrical signal source; sending, by the electrical signal source, in response to the first command, electrical signals to the switch array; providing, by the controller, a second command to the switch array; and sending, by the switch array, in response to the second command, electrical signals to a pre-selected set of electrodes in the electrode array at a frequency of IkHZ or more.

2. The method of claim 1, wherein the device comprises: a virtual reality or augmented reality system.

3. The method of claim 1, further comprising: receiving, by the controller, a selection of a device mode, the device mode including a first mode and a second mode, wherein the electrical signal source provides a constant voltage when the device is in the first mode, and wherein the electrical signal source provides a constant current at a frequency of lOkHZ or more when the device is in the second mode.

4. The method of claim 1, wherein the device comprises a stimulator, and the method comprises: delivering, by the stimulator, transcutaneous signals through the electrodes to a user.

5. The method of claim 4, further comprising: activating the electrodes using one or more channels to provide stimulation at varying positions.

6. The method of claim 1, wherein the device comprises: a wearable device.

7. The method of claim 1, wherein the electrodes form a scalable electrode array.

8. The method of claim 1, wherein the power supply comprises: a battery.

9. The method of claim 1, wherein the electrodes and a spacing between the electrodes comprises < 8mm.

10. A device for delivering high density electrical signals comprising: a controller; an electrical signal source electronically coupled with the controller; a switch array electronically coupled with the electrical signal source; an electrode array electronically coupled with the switch array; and a power supply powering the controller, the electrical signal source, and the switch array, wherein the controller executes instructions enabling operations including: providing power, by the power supply, to the controller, the electrical signal source, and the switch array; providing, by the controller, a first command to the electrical signal source; sending, by the electrical signal source, in response to the first command, electrical signals to the switch array; and providing, by the controller, a second command to the switch array; and sending, by the switch array, in response to the second command, signals to a pre-selected set of one or more electrodes in the electrode array at a frequency of IkHZ or more.

11. The device of claim 10, wherein the operations further comprise: receiving, by the controller, a selection of a device mode, the device mode including afirst mode and a second mode, wherein the electrical signal source provides a constant voltage when the device is in the first mode, and wherein the electrical signal source provides a constant current at a frequency of lOkHZ or more when the device is in the second mode.

12. The device of claim 11, wherein the operations further comprise: adjusting the constant voltage to provide a pre-selected current into and out of the electrodes.

13. The device of claim 11, wherein the device delivers bi-phasic square waves transcutaneously, the bi-phasic square waves reduce an impedance of a delivery surface, the reduced impedance is measured by the controller, and the controller lowers the constant voltage based on the reduced impedance.

14. The device of claim 11, further comprising: an ADC and a DAC electronically coupled with the controller; a current sensor electronically coupled with the controller; and a switch board electronically coupled with the controller; wherein the operations further include: measuring, by the ADC, a voltage across a resister in the current sensor; reading, by the controller, the ADC to measure a current; adjusting, by the controller, the voltage at the DAC to achieve a pre-selected current when the device is in the second mode; sending, by the controller, signals to the switch board; and connecting and latching, by the controller using a multiplexer, one or more channels to the one or more electrodes, the one or more electrodes electronically coupled with the switch board.

15. The device of claim 10 wherein the electrode array is scalable.

16. The device of claim 10, wherein the device comprises: a wearable stimulator.

17. The device of claim 10, wherein the power supply comprises: a battery.

18. The device of claim 10, wherein the operations further comprise: choosing the one or more electrodes arbitrarily from the electrode array for connection to one or more channels.

19. The device of claim 18, wherein the operations further comprise: activating the electrodes to provide stimulation at varying locations using one or more channels.

20. The device of claim 10, further comprising: a voltage module including a non-inverting amplifier having a pre-selected bandwidth and a pre-selected voltage; and a current module, wherein the voltage module and the current module are electronically coupled with the controller.

21. The device of claim 20, wherein a maximum output voltage comprises:± 32 V.

22. The device of claim 10, further comprising: closed loop control to monitor current passing through the electrodes.

23. The device of claim 10, wherein the switch array comprises: high voltage analog switches with low resistance.

24. The device of claim 10, wherein the power supply comprises: a 3.7V battery.

25. The device of claim 10, wherein the device provides signals to one or more of nerves, touch receptors, or muscles.

26. A computer-readable medium storing instructions for delivering high density electrical signals by a device, the device including a controller, an electrical signal source, an electrode array, a switch array, and a power supply, the instructions configured to be executed by a processor, the instructions comprising: providing power, by the power supply, to the controller, the electrical signal source, and the switch array; providing, by the controller, a first command to the electrical signal source; sending, by the electrical signal source, in response to the first command, electrical signals to the switch array; providing, by the controller, a second command to the switch array; and sending, by the switch array, in response to the second command, signals to a preselected set of electrodes in the electrode array at a frequency of 1kHz or more.

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