Systems and methods for generating event-CUE feedback loops

Abstract

Wearable devices designed for the somatosensory system aim to provide event-cue feedback electronics and therapeutic stimulation to the peripheral nervous system. This prompts a neurological response that is relayed back to the central nervous system. Devices precisely target peripheral mechanoreceptors by administering specific stimuli. Flexible electronics provide effective targeting which accounts for variations in mechanoreceptor density and type across different body locations. A sensing-actuation platform integrates soft carbon nanotube (CNT)-elastomer tactile sensors with custom flexible silicone-based actuators, enabling the creation of wearable electronics capable of delivering responsive feedback. Variably configured cantilevers of the actuators achieve a broad spectrum of driving frequencies. Three exemplary functional event-cue feedback devices - a prosthetic, sole, and glove - are presented, demonstrating a capability to utilize CNT sensors for detecting pressure variations from weight, gait, and grip. These devices transmit signals to flexible tactors, eliciting vibrotactile cues on healthy skin areas.

Description

[0001] SYSTEMS AND METHODS FOR GENERATING EVENT-CUE FEEDBACK LOOPS

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of US Provisional Patent App. No. 63 / 637,478, filed April 23, 2024, the complete contents of which are herein incorporated by reference.

[0004] FIELD OF THE INVENTION

[0005] The invention generally relates to haptic sensing and stimulating and, more particularly, systems and methods for assisting in the creation of event-cue feedback loops.

[0006] BACKGROUND

[0007] The somatosensory system plays a pivotal role in human perception, encompassing sensations from both the external environment and the body’s spatial orientation. In a healthy state, the central nervous system (CNS) sends efferent signals to motor neurons, initiating movement. Kinesthesia and tactile sensing, facilitated by mechanoreceptors in both glabrous and non-glabrous skin, are fundamental to this process. These receptors generate afferent signals conveying crucial data on pressure, temperature, vibration, weight, and limb positions back to the brain, constituting an essential feedback loop for maintaining balance, facilitating locomotion, and controlling grip strength. However, conditions such as Parkinson’s disease, peripheral neuropathy, prosthetic use, and environments lacking tactile feedback disrupt this loop, impairing somatosensory functioning. Consequently, there is a significant need for devices that can restore communication between the CNS and the peripheral nervous system (PNS) in such cases.

[0008] Nociceptors play a crucial role in signaling the brain about painful stimuli such as pressure, flexure, and temperature. For individuals with prosthetic limbs, particularly prosthetic legs, the absence of built-in feedback mechanisms poses a significant challenge. Without these mechanisms, users arc unable to detect potentially harmful pressure distributions that could damage the prosthetic or cause discomfort. This issue is particularly pertinent in cases where the entire body weight is regularly exerted on the sensitive interface between the prosthetic and the residual limb. Prosthetic legs designed to extend above the knee require joints capable of safely withstanding substantial physiological stress. While there have been efforts to incorporate pressure sensing mechanisms into prosthetic interfaces, current commercial solutions typically involve sending a signal to an interface or smartphone to issue a warning.

[0009] Among various actuation mechanisms, vibration stands out as an ideal medium due to its affordability, potency, and safety, making vibrotactile stimulation a preferred choice for delivering neurological stimulation to the PNS. Researchers are exploring the effectiveness of tactile stimulation devices in alleviating pain, sensation loss, and mobility issues in individuals with peripheral neuropathy. Studies have shown promising results in diabetic neuropathy, indicating that vibration therapy can enhance sensory function and reduce neuropathic pain, particularly when applied to affected areas like the feet. Moreover, vibration stimulation is being studied as an adjunct therapy for managing gait disturbances in Parkinson’s disease, with evidence suggesting its effectiveness in improving gait characteristics through enhanced tactile feedback to the CNS.

[0010] Existing market options for vibrotactile agents present a number of limitations and drawbacks. For instance, eccentric rotating mass (ERM) vibrators, while cost-effective and powerful, vibrate laterally, in plane due to the rotation of a magnet at high velocity, resulting in a higher minimum detection threshold compared to penetrative vibration into the skin. Existing linear resonant actuators (LRAs) that utilize solenoids for penetrative, axial vibration are rigid and operate efficiently only at a single resonant frequency, typically as coin-type vibrators. These commercial tactors arc typically bulky, rigid, and limited to a single resonant frequency. In contrast, dielectric elastomer actuators require high actuation voltages, posing safety risks, while pneumatic fluidic actuators have slow response rates and need high-pressure equipment.

[0011] SUMMARY

[0012] Some exemplary embodiments involve mechanical sensors triggering connected actuators to produce vibration. Some exemplary embodiments involve fabricating and integrating wearable, flexible electronics capable of combining tactile sensors and vibrators into a single platform. Exemplary integrated systems leverage a somatosensory event-cue feedback loop, where sensors mimic biological mechanosensors by responding to mechanical stimulation and transmitting signals to flexible actuators, thereby stimulating healthy skin areas and eliciting afferent signals to the CNS. In this feedback loop, the physical “event” involves various mechanical stimulations such as touch, weight loading, or gait (e.g., walking, running, ambulation, locomotion, etc.), which compress one or more sensors. Subsequently, the “cue” is the signal transmitted back to the brain via the vibration generated by one or more tactors in a secondary location on the body.

[0013] Embodiments provide wearable devices utilizing soft tactile sensing elastomers and flexible tactile vibrating actuators manufactured to create artificial neurological event-cue feedback loops for patients with limited peripheral nervous system function.

[0014] Some exemplary sensors transduce pressure from forces or activities such as but not limited to gait (e.g., walking, running, ambulation, locomotion, etc.), grip, and weight loading into electrical signals. These flexible sensors exhibit excellent physiological compatibility owing to their small size, flexibility, and customizability. An exemplary sensor exhibits a change in resistance proportional to the amount of pressure it is compressed or stretched under, allowing for precise quantification of incident pressure. Using a layered architecture, the sensor further enables ‘on-off functionality. Exemplary sensors may be produced by processes such as but not limited to 3D printing.

[0015] Some exemplary sensors utilize a carbon nanotube (CNT) -elastomer composite that converts compressive pressure into an electric signal. The flexible CNT composite possesses high flexibility and conductivity, enabling precise quantification of incident pressure through changes in resistance through the piezoresistive effect. An exemplary CNT-elastomer composite is disclosed in US2024 / 0093045A1, the complete contents of which are herein incorporated by reference.

[0016] An exemplary vibrotactile actuator is compact, flexible, and able to apply strong penetrative vibration, designed to vibrate various skin locations effectively at multiple vibration frequencies. Such a device ensures comprehensive stimulation for therapeutic purposes and event-cue feedback applications, particularly given the heterogeneous nature of glabrous skin, which exhibits varying sensitivity to different vibration frequencies and penetrating depth across different locations. Some exemplary embodiments entail delivery of vibration stimuli from small, flexible, and frequency-tunable vibrating actuators in exemplary devices of a wearable sole (including but not limited to an insole), gloves, and prosthetic socket. Some exemplary actuators deliver robust penetrative vibration at a resonant frequency of ~ 300 Hz, aligning with the peak sensitivity of the Pacinian corpuscle, a mechanoreceptor.

[0017] Embodiments include soft (i.e., flexible) electromagnetic actuators capable of generating localized vibrations on the body. Such devices offer advantages like fast response and low actuation voltages. Exemplary devices stimulate Meissner corpuscles to produce tapping-flutter- vibration sensations and Pacinian corpuscles for vibration or tickling sensations. Achieving this involves seamlessly integrating these actuators into a flexible electronic system using advanced manufacturing techniques and device physics, resulting in a portable and versatile systems and devices.

[0018] Materials of exemplary devices and components offer skin-friendly e-skin interface with flexibility and control. Exemplary devices include wearable circuitry produced on flexible substrates that seamlessly conform to non-planar surfaces. Exemplary systems may further include wearable bands designed for placement on the ankle, wrist, or thigh, for example.

[0019] Some embodiments integrate soft (i.e., flexible) tactile sensors and variable resonance frequency flexible tactors in an event-cue feedback loop. Devices integrating both tactile sensors and vibration actuators hold diverse applications across various sectors, including virtual reality (VR) and augmented reality (AR), gaming, healthcare, and wearable technology. In VR and AR, tactile sensors enhance user immersion by transducing touch from the user into a digital input, while vibration actuators simulate sensations like object interaction by providing haptic feedback. Gaming peripherals, such as controllers, benefit from these components, offering users more immersive experiences. For instance, tactile sensors detect in-game impacts, while vibration actuators simulate the sensation. In healthcare, tactile sensors provide pressure feedback in prosthetics, while vibration actuators deliver sensory alerts. In wearables like smartwatches, tactile sensors offer touch feedback, while vibration actuators discreetly provide notifications. Particularly for pain management and rehabilitation, devices with integrated soft tactile sensors and flexible vibration actuators can be used for pain management and rehabilitation therapies. Tactile sensors can detect pain or discomfort levels, while vibration actuators can deliver targeted vibrations or massage therapies to alleviate pain, promote circulation, and facilitate rehabilitation. Moreover, soft tactile sensors and flexible vibration actuators can be integrated into assistive technologies for individuals with disabilities or mobility impairments. For example, in prosthetic limbs or exoskeletons, tactile sensors can detect surface textures or pressure, while vibration actuators can provide sensory feedback to users, improving their mobility, balance, and proprioception.

[0020] Some exemplary embodiments may include a coding program implemented by one or more processors / controllers and circuitry to induce vibration under any pressure, pressure above a threshold, a difference in pressure between two sensors, and / or under other conditions. For example, a known voltage may flow through a voltage divider circuit. A program calculates the specific resistance by comparing the voltage drop across the power source and a known resistor. It then triggers a signal when the threshold is reached.

[0021] Exemplary embodiments may be implemented as wearable devices with various applications. Exemplary embodiments include a prosthetic socket, plantai' pressure sensing insole, and glove. Though these embodiments are designed for various body locations, they serve analogous functions. Each device establishes an event-cue feedback loop within regions of the body exhibiting reduced nervous system functionality. The responsive sensor-actuator systems are capable of interpreting mechanical stimuli and providing corresponding vibration feedback. Biomechanical compatibility ensures seamless integration with human tissues, vital for prosthetics and rehabilitation devices.

[0022] Some embodiments may provide feedback additional to that supplied by tactors. For example, an exemplary controller may send a user’s mobile device (e.g., smartphone) a notification (e.g., using a Bluetooth connection between the exemplary feedback loop device and the user’s smartphone) upon compression of a pressure sensor above a specified / predefined threshold indicative of potentially unsafe mechanical stress conditions. Other information may be shared with user devices. For instance, a pressure distribution gradient read from an array of pressure sensors can be relayed to a user device like a smartphone in real time. Following a vibration cue, and reactive body change, a user can check his or her mobile device to identify the source of the vibration warning from the system.

[0023] Some exemplary embodiments revolutionize sensory feedback for individuals with neurological disorders by integrating hair-like tactile sensors and a vibration actuation system into a flexible e-skin spider-leg-inspired system. This innovative approach promises customizable sensory feedback, improving motor control, sensory rehabilitation, and prosthetic device functionality. A design featuring sensors in arrays or networks enables scalable deployment, increased coverage, and comprehensive monitoring of multiple signals and regions. This advancement facilitates assistive technologies for proprioception and balance enhancement, aiding sensory retraining and guiding targeted movements. The flexibility and conformability of the system ensure reliable and continuous data collection, empowering healthcare professionals with essential real-time information for customization.

[0024] In some exemplary embodiments, sensors are coupled with custom tactile actuators featuring a flexible shell and customizable vibrating cantilevers, providing a broad spectrum of sizing options and vibratory behaviors. With actuator diameters ranging from ~ 10 mm down to 4 mm, the finished tactors exhibit exceptional flexibility. Cantilever designs offer resonant peaks spanning from ~ 100 to ~ 425 Hz and are capable of delivering penetrative, out of plane vibration at an average depth of ~ 29.3 pm, for example. Actuators are connected to wearable alternating current (AC) signal generators and wireless transceivers (e.g., Bluetooth chips) through flexible electrodes.

[0025] Three exemplary functional event-cue feedback devices are disclosed: a prosthetic, sole, and glove. All three utilize one or more sensors to detect incident pressure, the information from which is transmitted to one or more flexible tactors positionable on a healthy portion of skin to deliver a vibrotactile cue to the user. The prosthetic responds to a change in pressure on the socket incident from an unsafe posture and induces actuation in the healthy innervated quadriceps. The flexible sole connects plantar sensors that monitor pressure from gait and induce vibration on the dorsum of the foot. Finally, the glove houses pressure sensors that, upon compression, send a signal to a second glove to induce vibration on the fingertips. These and analogous systems not only propel the advancement of wearable technology but also deliver consequential solutions for diverse fields such as prosthetics, mobility aids, and assistive technology. The implementation of these devices, combined with the event-cue feedback loop, demonstrates potential in revitalizing impaired peripheral nerves, enhancing prosthetic capabilities, and improving tactile perception in individuals with restricted nervous system function.

[0026] According to at least on exemplary embodiment, a wearable system for generating a somatosensory event-cue feedback loop comprises one or more flexible sensors configured to convert mechanical pressure into electrical signals; one or more flexible electromagnetic actuators configured to deliver vibratory stimulations that change based on the electrical signals from the one or more flexible sensors; and one or more alternating current (AC) signal generators for powering the one or more flexible electromagnetic actuators. The one or more flexible sensors may be configured to have an ‘on’ state in which the one or more flexible sensors behave as variable resistors and an ‘off’ state in which the one or more flexible sensors behave as a circuit break. At least one sensor of the one or more flexible sensors may comprise a first carbon nanotube (CNT)-elastomer composite layer; a second CNT-elastomer composite layer; and an insulating divider separating the first and second CNT-elastomer composite layers. At least one actuator of the one or more flexible electromagnetic actuators may comprise a flexible solenoid; a magnet; and a flexible support to which the magnet is affixed, and which is configured to permit but limit displacement of the magnet relative to the flexible solenoid. The flexible solenoid may comprise wire wound about a flexible body. The flexible body may comprise silicone walls. The at least one actuator may have a diameter of 4-10 mm. The flexible support may be configured as a pair of cantilevers. The one or more flexible electromagnetic actuators may have a spectrum of driving frequencies. The one or more flexible electromagneticbased actuators may collectively have resonant peaks spanning at least 100-425 Hz. The one or more flexible sensors may be wired or wirelessly linked to the one or more flexible electromagnetic actuators. The electrical signals may induce vibration under any non-zero pressure, pressure above a threshold, or a difference in pressure between at least two of the one or more flexible sensors. The wearable system may further comprise a prosthetic socket in which the sensors are arranged to sense weight loading from a residual limb in a state of use; an insole with the one or more flexible sensors arranged to detect plantar pressure on the insole in a state of use; or a first glove configured for pressure sensing during gripping using the one or more flexible sensors. For the latter configuration, the wearable system may further comprise a second glove configured to vibrate with the one or more flexible electromagnetic actuators in response to gripping force detected by the first glove.

[0027] According to at least on exemplary embodiment, a method of generating a somatosensory event-cue feedback loop comprises converting pressure caused by forces from gait, grip, or weight loading of a user into electrical signals with one or more flexible sensors; and delivering vibratory stimulations to the user with one or more flexible electromagnetic actuators, the vibratory stimulations changing based on the electrical signals from the one or more flexible sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1A is a non-limiting example of an apparatus providing a sensing-actuation feedback loop for a user.

[0029] Figure IB is a diagram which expands on the principle of operation of exemplary embodiments like the apparatus of Figure 1A which are configured to play a role in the physiological process of event-cue feedback loops.

[0030] Figure 2A is a schematic of an exemplary pressure sensor.

[0031] Figure 2B depicts the sensor of Figure 2A in both an uncompressed / “off” state (figure left) and compressed / “on” state (figure right).

[0032] Figure 3 A depicts a schematic of an exemplary tactor in a partially exploded view.

[0033] Figure 3B is a schematic illustrating the operation of an exemplary tactor which involves a magnetic field produced by a solenoid.

[0034] Figure 3C is a visual of an oscillating magnetic body of tactor actuating against a user’s skin and achieving a penetration depth adequate to produce sensation for generating an event-cue feedback loop.

[0035] Figure 4 A is a flow diagram of an exemplary process for manufacturing a tactor.

[0036] Figure 4B depicts precision solenoid wrapping, part of an exemplary process of manufacturing a tactor.

[0037] Figure 5 illustrates an instance of 3D printing flexible electronics for an exemplary glove embodiment.

[0038] Figure 6 is an image comparing two exemplary sizes of tactor according to this disclosure alongside two commercially available vibrators.

[0039] Figure 7 is one illustrative example for a wired one-to-one pairing of sensor and actuator.

[0040] Figure 8 is a circuit diagram of one illustrative example for a wireless sensor circuit / module.

[0041] Figure 9 is a circuit diagram of one illustrative example for a wireless actuator circuit / module.

[0042] Figures 10A and 10B illustrate an exemplary system comprising a prosthetic socket in which compression sensors are embedded, the signals from which are used to control timing and parameters of stimulatory vibrations delivered by an array of tactors arranged apart from the socket.

[0043] Figures 11 A, 1 IB, and 11C show yet another exemplary system involves a plantar pressure sensor array implemented in an insole.

[0044] Figures 12A and 12B illustrate an exemplary system comprising a glove equipped with pressure sensors linked to a second glove that vibrates in response to gripping force detected by the first glove.

[0045] Figure 13 is a geometric depiction of one exemplary configuration of the support to which a tactor’s oscillating body is attached.

[0046] Figure 14A shows a prototype sensor subject to different levels of compression from a fingertip.

[0047] Figure 14B shows real-time data from the three separate compressions depicted by Figure 14A.

[0048] Figure 15 shows data for a prototype system including the force to which a sensor was subjected by mechanical compression from a texture analyzer, current through the system, and vibration produced by a connected tactor.

[0049] Figures 16A-16E show the frequency-dependent vibration and resonance behavior of differently configured tactors.

[0050] DETAILED DESCRIPTION

[0051] Figure 1A is a non-limiting example of a system for generating a sensing-actuation feedback loop with a user. Flexible pressure sensors 101 (e.g., configured as sensing pads) exhibit changes in resistance when subjected to compression, tension, or flexure. The sensors 101 provide the system with an awareness of the user’s weight distribution 102. Actuators 103 each employ an oscillating magnetic field generated by a solenoid which drives a magnetic object (e.g., a magnet) and induces vibration 104. The actuators 103 are arranged proximal to healthy tissue of the subject so that the vibrations 104 are perceived by the user’s peripheral nervous system (PNS) 105. The sensing-actuation feedback loop created by sensors 101 and actuators 103 is configured for cueing the PNS 105 with information about the weight distribution 102 of which the user would be unaware in the absence of the system. Figure IB is a diagram which expands on the principle of operation of exemplary embodiments like the system of Figure 1 A which arc configured to play a significant role in the physiological process of event-cue feedback loops. In this loop, flexible electronics facilitate the transduction of a physical process from one area of the body with limited or no nervous system sensitivity to another area with normal sensitivity. The loop is depicted in Figure IB, which also depicts a few example devices connected to a user. Exemplary devices include but are not limited to a prosthetic socket feedback apparatus 100, a plantar pressure sensing insole 110, and a glove-based grip control apparatus 120. As a non-limiting example, loop initiation may occur with the central nervous system (CNS), specifically the brain 151, signaling 152 an action to the body through an efferent pathway (e.g., weight shifting, limb movement, or grip application). The physical action (e.g., weight shifting, limb movement, grip application, etc.) of the user affects the apparatus 100, 110, or 120. In particular, the physical action results in forces which are sensed by the pressure sensors of the apparatus 100, 110, or 120. The data from this sensing 153 is passed forward to trigger actuation 154, e.g. vibration, via customizable tactile actuators. For purposes of this disclosure, “tactor” may be used to refer to an exemplary actuator characterizable as tactile, vibrotactile, haptic, or vibrohaptic. The tactors generate vibration on a healthy portion of the skin, eliciting an afferent cue through the PNS. This cue 155 is then received by the CNS, completing the loop as it adjusts the signal sent by the brain through an efferent pathway back to the PNS. The apparatus 100, 110, or 120 may include analog and / or digital circuitry 111 which is configured to receive the sensing 153 data from the sensors and send actuation 154 signals to the actuators which vary based on the sensing 153 data.

[0052] To artificially replicate aspects of the event-cue feedback pathway of the natural body, the apparatuses 100, 110, and 120 employ elements with contrasting principles: sensors and actuators. Sensing involves transducing a physical signal (e.g., compression, tension, flexure) into an electrical signal, whereas actuation involves transducing an electrical signal into a physical signal (e.g., vibration, compression, fluid pressure).

[0053] Exemplary sensors operate by transducing pressure using a particular principle. According to some embodiments of this disclosure, sensors utilize flexible elements (e.g., pads) made from ink infused with CNTs, which are then produced (e.g., 3D printed) to create compressible structures. When these pads are compressed, the sensor's resistance changes under constant voltage through the piezoresistive effect. The degree of this resistance (R) alteration can be accurately gauged, enabling precise determination of the applied pressure for any given signal. To enable actuation, an exemplary actuator includes a solenoid that converts AC current from a looped wire into a fluctuating magnetic field. This magnetic field’s oscillation propels a magnet vertically, inducing vibrations at a specific frequency corresponding to the AC signal. The integration of these two distinct principles are integrated into wearable and functional devices configured with flexible electronics. Higher pressures generate more vibration and therefore more substantial feedback signals to the brain, mirroring the scaled response of human biological systems.

[0054] Figure 2A is a schematic of an exemplary sensor 200. Figure 2B depicts the sensor 200 in both an uncompressed / “off ’ state (figure left) and compressed / “on” state (figure right). An exemplary pressure sensor 200 transitions between ‘off’ and ‘on’ states under compression while still exhibiting a change in resistance with increasing compression strength. An exemplary geometry for sensor 200 is a layered architecture. Two conducting components 201 and 202 are separated by an insulating layer 203 that introduces ‘on-off’ modality. Exemplary conducting components 201 and 202 are thin carbon-nanotube (CNT) composite cylinders / disks / pads. An exemplary separating insulating layer 203 is a small insulating silicone divider. This divider effectively opens the circuit (i.e., acts as a circuit break) when the sensor 200 is uncompressed. The true “off’ state when no compression is present is advantageous for ensuring that one or more tactors only receive current and produces vibration when pressure is actually being applied to a sensor 200. However, the CNT pads 201 and 202 come into contact with one another and close the circuit under compression (even slight compression). Moreover, a change in pressure on the CNT composite alters its specific resistance, thereby affecting the amplitude of the current through the circuit element.

[0055] Exemplary pressure sensors for applications of this disclosure possess high flexibility and conductivity. For at least some embodiments, exemplary pressure sensors are also compatible with 3D printing techniques for customizable wearable sensing. For instance, the CNT composite layers 201 and 202 may be 3D printed. As non-limiting examples of electrical leads / electrodes 205 to and from the components 201 and 202, copper (Cu) tape may be adhered to the CNT composite using, e.g., silver paste adhesion. The dimensions of the pressure sensor are desired to be customized to suit the requirements of the event-cue feedback loop. An exemplary material for the two conducting components 201 and 202 is a CNT- clastomcr composite. For instance, a suitable CNT-clastomcr composite is disclosed in A. Shar, P. Glass, S. H. Park, D. Joung, Adv. Funct. Mater. 2023, 33, 2211079. This exemplary composite exhibits a Young’s Modulus of ~ 2 MPa, a conductivity of ~ 7 Sm"1, and can be easily printed at room temperature without requiring additional post-processing steps.

[0056] An exemplary but nonlimiting example process for producing CNT-elastomer composite is as follows. Amino-functionalized multi-walled carbon nanotubes with a diameter of e.g. 20 nm and a length ranging from e.g. 1 to 12 pm are blended with butyl acetate and subjected to sonication to form a CNT-butyl acetate slurry. A separate mixture is prepared by combining butyl acetate, alkoxy-cure room temperature vulcanized (RTV) silicone, and methyl-terminated polydimethylsiloxane. These mixtures are combined and mixed. The resulting viscous liquid, comprising CNTs, butyl acetate, methyl-terminated poly dimethyl siloxane (MEP), and RTV silicone in a homogenous dispersion, has the butyl acetate removed (e.g., by evaporation). The resulting medium is a 3D-printable ink.

[0057] Exemplary sensors do not include bulk strain sensors. Using a bulk strain sensor in series with a tactor would not yield the desired feedback. In such a setup, there would be a persistent latent current through the tactor, resulting in continuous vibration even when the sensor is relaxed.

[0058] Figure 3A is a partial exploded view of a schematic representation of an exemplary tactor 300. The tactor 300 comprises a flexible body 301, a conductive coil 302, and a magnet 303. A flexible support 304 is connected with the flexible body 301, and the magnet 303 is affixed to the support 304, e.g., on the bottom of the support 304 according to the orientation of sensor 300 in Figure 3A. The support 304 is configured to permit but limit displacement of the magnet 303 relative to the coil 302. The coil 302 is wrapped about and supported by the flexible body 301. The coil 302 is configured to act as a solenoid when carrying electric current. The tactor 300 may be wrapped or encased with a flexible shell 305 for protection and insulation of the conductive coil 302. The tactor 300 may be characterized as a linear actuator. Exemplary tactors may be configured to flex up to at least 26.8% or up to at least 50.4% of original height under a 20 N force without permanent deformation or damage. The customizable and flexible vibrohaptic tactors are designed to deliver frequency-dependent vibrations to human skin. The flexible body 301 may be, for example, silicone or a silicone-based material. The flexible support 304 connected with the body 301 may likewise be made of, for example, silicone or a silicone-based material. Both the body 301 and support 304 may be produced together, e.g., during the same 3D printing process. The support 304 may be configured as one or more cantilevers (e.g., a pair of cantilevers), a configuration discussed in greater detail below in connection with Figure 13.

[0059] Figure 3B is a schematic illustrating the operation of an exemplary tactor which involves a magnetic field produced by a solenoid. One of the primary challenges in designing vibrohaptic tactors is to generate sufficient vibration for detection and differentiation (from other tactile inputs including other vibration frequencies and intensities by the same or complementary tactors of the same device) by living tissue while maintaining a compact and wearable form factor. Achieving this requires the creation of a strong magnetic field within the tactor’ s solenoid, which is generated by the Lorentz force from the coaxial coils of wire. The dimensions of the coil are imposed by the size of the tactor’ s body, which is customizable to different embodiments.

[0060] Figure 3C is a visual of the magnet 303 of tactor 300 actuating against a user’s skin 330 and achieving a penetration depth adequate to produce sensation for generating an event-cue feedback loop. Figure 3C omits from illustration other elements of the tactor 300. Parameters such as the height, radius, and number of turns in the solenoid influence the resulting magnetic field that drives magnet 303. For instance, a magnet would experience a slightly stronger electric field at the edge of a shorter solenoid than at the edge of a taller solenoid with the same number of turns as the shorter solenoid. Exemplary solenoid heights for tactors of this disclosure include but are not limited to heights (z) of 4-20 mm. Exemplary solenoid radii for tactors of this disclosure include but are not limited to a fixed radius of 2-10 mm. Smaller radii produce denser and more intense magnetic fields. Smaller radius bodies are capable of generating higher- intensity vibrations with the appropriate magnet. Exemplary solenoid number of turns (N) for tactors of this disclosure include but are not limited to 100-1000 turns or 200-1000 turns. Exemplary magnetic field strengths for tactors of this disclosure include but are not limited to 0.420-1.46 mT. The magnetic field strength within a solenoid typically increases with the number of turns (N), but this relationship is subject to geometric limitations. As the number of turns increases, so does the length of the wire, resulting in greater resistance and consequently a decrease in current. However, in solenoids with a sufficient number of turns (e.g., N = 200- 1000), the magnetic field remains relatively unchanged. There are slight changes for real non- idcal solenoids. This said, there arc significant changes in the thermal properties of solenoids wrapped with different numbers of turns. Embodiments may be manufactured with a greater number of turns for the particular purpose of reducing the operating temperature of the tactor. Increasing the number of turns enhances safety during operation, even at elevated voltages. Stronger and heavier magnets may also be used for producing larger vibrations where desired depending on the embodiment. Exemplary maximum vibration acceleration at resonance includes but is not limited to 4-8 m / s2.

[0061] Figure 4A is a flow diagram of images summarizing an exemplary manufacturing process for production of a tactor 300. First the flexible body 301 is produced by 3D printing of silicone. The flexible body 301 is connected to a flexible silicone support 304 during printing. After the silicone has cured, the flexible body 301 is loaded onto a rotatable mount 411. The flexible body 301 is then rotated as thin (e.g., ~50 pm diameter) wire (e.g., Cu wire) is wrapped about the flexible body 301. Figure 4B shows a wire spool 412 from which wire 413 is fed. The wire 413 is fed through a tip 414 which guides the wire 413 and minimizes risk of the wire breaking during the wrapping process. Referring again to Figure 4A, after the desired number of loops of wire have been wrapped coaxially about the flexible walls of the flexible body 301, a magnet (e.g., a permanent magnet) is affixed to the flexible support 304. Prior to or after the affixing of the magnet, the copper wire may be coated with a shell of flexible material such as further silicone so that the wire is shielded from risk of contact with the environment.

[0062] Other elements of exemplary embodiments may be produced by 3D printing besides the bodies of some exemplary tactors. For example, in Figure 5, an instance of 3D printing flexible electronics is depicted. Flexible silver microparticle ink is applied onto the surface of a rubber nitrile glove, connecting pressure sensors 200 near fingertips of the glove to terminals located on the wrist of the glove.

[0063] Component size has special consequence in the context of wearable devices. In the context of wearable haptic feedback devices, size takes on even greater importance. For instance, overlarge tactors may stimulate too great an area of user skin surface to provide sufficiently detailed information to the user’s CNS. To generate a meaningful event-cue feedback loop, it is important that the tactors involved are especially small. Figure 6 is an image comparing two exemplary sizes of tactor according to this disclosure alongside two commercially available vibrators. From left to right Figure 6 shows a 4 mm diameter tactor 601 (made according to Figures 4A / 4B), a conventional coin-type vibrator 602 (~ 8 mm diameter), a 10 mm diameter tactor 603 (also made according to Figures 4A / 4B), and a current market-available C2™ tactor 604 (~ 30 mm diameter). The tactors 601 and 603 are not only less than half the size of the C2 tactor 604, the tactors 601 and 603 are more flexible than both the coin-type actuator 602 and C2 tactor 604. Exemplary diameters of tactors for embodiments of this disclosure include diameters of 4-10 mm, for example. This compact size facilitates the fabrication of wearable devices suitable for use across various body areas. This small size enables the delivery of tactile vibration to areas where larger and less flexible tactors, like the C2 tactor, may not be suitable. Considering the vibration strength per unit area, even the small tactor 601 demonstrates potential for delivering robust vibration in applications such as but not limited to covering the surface of a fingertip with such tactors or inducing multi-frequency vibrations within a small area.

[0064] In some embodiments, exemplary apparatuses include wired connections between sensors and actuators. Figure 7 is one illustrative example for a wired one-to-one pairing of sensor and actuator.

[0065] Figure 7 depicts an apparatus 700 comprising at least one sensor 701 connected in series with at least one actuator 702. The device 700 is driven by alternating current (AC) from at least one power source 703. A change in pressure on the CNT composites of the sensor 701 alters its specific resistance, thereby affecting the amplitude of the current through the circuit elements. The intensity of vibration (corresponding with the magnitude of displacement of the magnet in the actuator 702) varies with the variation in current amplitude. Accordingly, greater pressure exerted upon sensor 701 translates immediately to greater current amplitude and therefore greater vibration intensity from actuator 702. Less pressure exerted upon sensor 701 translates immediately to less current amplitude and therefore less vibration intensity from actuator 702. Alternative embodiments may have one sensor connected and affecting the vibration response of multiple actuators. Alternative embodiments may instead or additionally have multiple sensors connected and affecting the vibration response of one actuator.

[0066] In some embodiments, exemplary systems include wireless connections between sensors and actuators. Figure 8 is a circuit diagram of one illustrative example for a wireless sensor circuit / module 800. A controller 801 regulates power from a power source 802 (e.g., a small battery) for providing a current through resistors 803 and 804. Resistor 803 is a variable resistor. Variable resistor 803 represents the compression sensor, e.g., sensor 200 described above in connection with Figures 2A and 2B, for example. The controller 801 includes a wireless module such as a Bluetooth chip / card for wireless communication with one or more complementary circuits, in particular one or more actuator circuits / modules.

[0067] Figure 9 is a circuit diagram of one illustrative example for a wireless actuator circuit / module 900. A controller 901 regulates power from a power source 902 (e.g., a small battery). The inductor element 903 is a physical transducer for delivering vibrohaptic signals to a user. The inductor 903 may be configured consistent with actuator 300 described above in connection with Figures 3A and 3B, for example. The controller 901 includes a wireless module such as a Bluetooth chip / card for wireless communication with one or more complementary circuits, in particular one or more sensor circuits / modules such as one or more sensor modules 800 of Figure 8. The actuator circuit / module 900 may include further elements such as resistor 904 and MOSFET 905 which, in coordination with controller 901, coordinate timing and parameters of signals delivered to inductor 903 so they correspond in timing and intensity (e.g., amplitude) with electronic signals being received by controller 901 from one or more sensor modules like sensor module 800 of Figure 8. An AC signal generator 906 is interposed between inductor 903 and a remainder of the circuit 900 which operates on direct current (DC). The AC signal generator 906 ensures the inductor 903 is driven with AC current so that the inductor produces an oscillating magnetic field. An exemplary wearable AC generator may generate a frequency-tunable signal ranging from 10 Hz to 1 MHz, for example, featuring a well-preserved sinusoidal current pattern within the voltage range of -2V to 2V, for example.

[0068] Figures 10A and 10B illustrate an exemplary system 1000 comprising a prosthetic socket 100. Compression sensors 101 are embedded / secured on an interior 1012 of the prosthetic socket 100. This embodiment is particularly advantageous for users with compromised nociception. Nociceptors are sensory nerve endings that detect harmful stimuli and transmit signals to the brain to create the sensation of pain. Nociceptors play a crucial role in signaling the brain about painful stimuli such as pressure, flexure, and temperature. For individuals with prosthetic limbs, particularly prosthetic legs, the absence of built-in feedback mechanisms poses a significant challenge. Without these mechanisms, users are unable to detect potentially harmful pressure distributions that could damage the prosthetic or cause discomfort or harm to the residual limb. This issue is particularly pertinent in cases where the entire body weight is regularly exerted on the sensitive interface between the prosthetic and the residual limb. Prosthetic legs designed to extend above the knee require joints capable of safely withstanding substantial physiological stress.

[0069] The system 1000 is configured for immediately alerting users to unsafe pressure levels. The soft sensors 101 are configured to convert compressive pressure into electrical signals. The flexible electromagnetic-based actuators 103 are configured to deliver vibratory stimulations that change based on the electrical signals from the soft sensors. The sensors 101 and actuators 103 may be hardwired to one another, as was depicted by way of example in Figure 1A. Alternatively, sensors 101 and actuators 103 may be wirelessly connected.

[0070] System 1000 of Figures 10A and 10B illustrates an exemplary wireless configuration. The sensors 101 (of which three are illustrated, though in practice embodiments may have fewer or greater than three separately positioned sensors 101) are wired to a sensor control module 1011. The sensor control module 1011 houses a power supply, wireless (trans Receiver such as but not limited to a Bluetooth chip, and related circuitry (see, for example, the circuit 800 of Figure 8 for a comparable arrangement). Sensor control module 1011 communicates wirelessly with tactor control module 1031. The prosthetic socket 100 may provide the structure for supporting and maintaining the positions of the sensors 101 and the module 1011. Broken lines are used in Figure 10A to indicate wiring connections and module 1011 which are on back exterior of the prosthetic socket 100 and thus not technically visible from the viewing angle in Figure 10A.

[0071] Tactor control module 1031 is wired to a plurality of tactors 103 (of which three are illustrated, though in practice embodiments may have fewer or greater than three separately positioned tactors 103). The tactor control module 1031 houses a power supply, wireless (trans)receiver such as but not limited to a Bluetooth chip, and related circuitry (see, for example, the circuit 900 of Figure 9 for a comparable arrangement). A wearable band 1001 provides the structure for supporting and maintaining the positions of the tactors 103 and the module 1031. Figure 10B includes depiction of a user’s thigh 1050 about which the band 1001 is worn. When the system 1000 detects an unsafe pressure level or distribution in the prosthetic socket 100, the system 100 delivers a vibration event cue, and the user can change posture in reaction. Figures 1 1 A, 1 IB, and 11C show yet another exemplary system 1 100. System 1 100 involves a plantar pressure sensor array implemented in an insole 110. Plantar pressure sensors can play a crucial role in providing somatosensory feedback during steady-state walking, particularly for individuals with mobility impairments. Furthermore, direct vibratory stimulation from these sensors is significant in therapeutic contexts, such as for individuals with Parkinson’s disease. Wearable vibration stimulation devices like system 1100 can have a positive impact on Parkinson's patients’ balance and gait.

[0072] Figure 11 A shows a bottom side of insole 110, whereas Figure 1 IB shows a top side of the insole 110. Pressure sensors 1101 are placed at multiple separate positions on the insole 110. For non-limiting illustration, Figures 11A and 11B show sensors placed at six different locations respectively labeled i, ii, iii, iv, v, and vi. Positions of sensors may include but are not limited to the heel, the arch, the toes, and the ball of the foot. During compression from the user’s weight, the pressure sensors embedded in the sole 110 record distinct current readings for each of the positions i through vi across the user’s sole. Current values from the sensors are converted to pressure readings.

[0073] As depicted in Figure 1 IB, the system 1100 further comprises an array of tactors that vibrate upon compression of the sole. Exemplary connections 1104 include but are not limited to, for example, 3D-printed electrodes and silicone bridges linking the tactors with the sensors. The system may be powered by one or more portable batteries and include such other circuitry as already discussed above, e.g., a tunable (frequency adjustable) AC generator. Besides delivering vibration to a user’s skin surfaces, exemplary embodiments like system 1100 may provide additional forms of feedback which may be helpful to the understanding of a user about his or her condition and to medical professionals who assist in the user’s healthcare. For example, the pressure sensor readings and / or related visuals, such as a pressure heat map superimposed onto the sole model, may be provided and enable real-time monitoring via a user’s mobile device such as but not limited to a smartphone. The system 1100 may include a wireless card which enables communication with such mobile devices.

[0074] Figure 11C shows the system 1100 in a state of use. Pressure on the sensors on the insole are immediately translated to vibration feedback on the top of the user’ s foot by the arranged tactors 1103. Exemplary embodiments like system 1100 may be configured to allow for variation in vibration frequency and / or vibration amplitude at multiple varied positions on the patient. Such embodiments permit customization of stimulation parameters based on individual patient needs required to enhance gait characteristics, for example.

[0075] An insole 110 may be produced according to a selection of standardized sides. Alternatively, an insole 110 may be customized to individual users. For instance, a user’s foot may be scanned using 3D scanning software. An insole is then 3D printed, tailored to the specific size of the foot, with silicone, for example.

[0076] Figures 12A and 12B illustrate a further exemplary embodiment, in this case a system 1200 comprising a glove 120 equipped with pressure sensors 1201 linked to a second glove 120' that vibrates in response to gripping force(s) detected by glove 120. Individuals experiencing neuropathy in a hand or those using a prosthetic often struggle with gauging the appropriate amount of force required for gripping objects. The sensation of grip is a well-regulated interplay between force exertion and slip detection which allows for precise control of how objects are held by a hand. Additionally, fingertips play a crucial role in providing sensory feedback regarding surface characteristics such as texture, shape, and stiffness with tactile cueing. An event cue feedback system like system 1200 depicted by Figures 12A and 12B which transduces pressure data from a glove and transfers it to a healthy sensitive part of the body, such as but not limited to a user’s other hand, is advantageous to aid in grip control and in tactile sensing.

[0077] The first glove 120 (depicted for nonlimiting illustration as configured for the left hand in Figures 12A / 12B) is configured for pressure sensing and therefore has pressure sensors 1201 positioned at importation positions such as the fingertips. The current values resulting from compression between each fingertip and an object (e.g., an apple in the case of Figure 12B) during gripping are read by sensor control module 1211. The second glove 120' (depicted for nonlimiting illustration as configured for the right hand in Figure 12B) is configured to vibrate in response to the gripping force(s) detected by the first glove 120. The vibrations are delivered via tactors 1203, control signals to which are sent from tactor control module 1231. The control module 1231 includes a portable AC source and wireless transceiver for communication with the control module 1211 of the opposite glove. Programming on either or both control modules may permit modifying the trigger input from the pressure sensors 1201. For instance, if the gripped object were to slip due to insufficient pressure, resulting in a drop in current in one or more fingertips, vibration could be induced. Alternatively, any current flow resulting from compression could prompt vibration in the fingertips, continuously informing the user that he or she is gripping an object with adequate pressure.

[0078] Exemplary tactors and a variety of exemplary applications of such tactors are discussed above. As introduced with Figures 3A-3C and 4A-4B, an exemplary tactor may include an oscillating body such as but not limited to a magnet (such as a permanent magnet). The oscillating behavior of the oscillating body is determined by a number of features of the tactor. Among these is the support to which the oscillating body is attached.

[0079] Figure 13 is a geometric depiction of one exemplary configuration of the support 1304 to which a tactor’ s oscillating body is attached. The support 1304 has a symmetrical geometry. The support 1304 may be characterized as two triangular shaped cantilevers, each extending from an opposite wall of tactor body walls 1301, which meet at their distal tips. Support 1304 may be characterized as having a “bowtie” shape. Support 1304 may be varied with respect to the cantilever angle 0 depicted in Figure 13. The resonant frequency of the tactor with support 1304 is characterized by the equations in Figure 13. The tactor configuration depicted by Figure 13 is a platform for developing tactors with a broad range of strong penetrative vibrations at more than a single resonance frequency. For tactors which implement the support configuration depicted by Figure 13, the cantilevers that the magnet is adhered to may be customized to have a particular spring constant and thus different resonance peak(s) from other tactors due to this changing oscillatory behavior. According to the behavior of an ideal spring, the fRincreases with the spring constant (fc), as described by the equation: fR^k / m

[0080] (where m is the mass of the cantilever-magnet system). The fRof the tactor is governed by its physical parameters, such as Young's modulus and shape. The shape of the cantilever, in particular, exerts a significant influence on fRsince it undergoes the majority of stretching during vibration (actuation). The fRincreases directly, though not necessarily proportionally, with the cantilever angle (0). A tactor with a tunable fRcan precisely target vibrating specific locations of glabrous skin on the body, each with its own sensitivity to varying vibration frequencies.

[0081] The resonance peak (R) shifts noticeably towards higher frequencies with increasing cantilever angle (0), correlating with an expected increase in spring constants. A linear relationship exists with increasing k corresponding to increasing cantilever angles (0). A stronger vibration force results from a smaller spring constant (k), as evidenced by displacement decreasing notably with increasing 0. Additionally, the resonant peak broadens significantly as the 0 increases.

[0082] EXAMPLES

[0083] Example 1. A Prototype Flexible CNT Pressure Sensor

[0084] Prototype flexible CNT pressure sensors were produced as follows. Aminofunctionalized multi-walled carbon nanotubes (CheapTubes), with a diameter of approximately 20 nm and a length ranging from 1 to 12 pm, were blended with butyl acetate (Sigma Aldrich; W217409; WI, USA) at a ratio of 1:100 w / w and subjected to 15 minutes of sonication (Branson; M38OO; 40kHz) to form a CNT-butyl acetate slurry. Meanwhile, a separate mixture was prepared by combining butyl acetate, alkoxy-cure room temperature vulcanized (RTV) silicone (Dow; DOWSIL 738 Electrical Sealant), and methyl-terminated poly dimethyl siloxane (lOOcSt; Sigma Aldrich; 378364) in a weight ratio of 50:100:15. The resulting viscous liquid, comprising CNTs, butyl acetate, methyl-terminated polydimethylsiloxane (MEP), and RTV silicone in a homogenous dispersion, was spread onto several Petri dishes and placed in a vacuum chamber until the butyl acetate had evaporated. The final ink was then scraped from the Petri dishes and transferred to a syringe. The CNT pressure sensors were fabricated by affixing two 3D-printed CNT-silicone pads onto copper tape and isolating them with a silicone divider. Pressure was applied to the sensors by a finger at increasing intensity while measuring the current between the Cu tape terminals using a source meter (2470 SMU; Keithley). The sensor setup was completed by soldering wires and a battery to a Bluetooth chip. Similarly, the AC generator was assembled by soldering a battery and Bluetooth chip to a commercially available AC signal generator (Gwinetek MFG-2260MRA) and encased in a 3D printed resin housing attached to a wearable band.

[0085] Figure 14A shows a prototype sensor’s response to compression from a fingertip. Figure 14B shows real-time data from the three separate compressions depicted by Figure 14A. As the CNT pads come into contact under pressure, the current gradually rises from 0 to - 2.75 mA under light pressure, ~ 4.41 mA under medium pressure, and around ~ 5.84 mA under strong pressure. It is noteworthy that the current returns to ~ 0 mA upon release.

[0086] Example 2. A Prototype Flexible CNT Pressure Sensor and Responsive Vibrating Tactor Systems in a Feedback Loop For this Example, a simple series circuit was configured with connection of a prototype CNT sensor (sec Example 1) to a prototype tactor.

[0087] The prototype tactor was produced as follows. Medium and small-sized tactor bodies were produced using direct ink writing (DIW) with RTV silicone employing a custom robot gantry (A351, Physik Instrumente L.P.). Printing pressures ranged from 0.1 to 300 psi using a pneumatic dispensing system (Ultimus V; Nordson EFD; OH, USA). The ink was extruded through various plastic tapered nozzles with inner diameters ranging from ~ 200 pm to ~ 1.60 mm, as well as metal nozzles with inner diameters of 100 pm and 150 pm (Nordson EFD; OH, USA). Upon completion of the printing process, the prints were allowed to cure under ambient temperature and humidity conditions for 24 hours. The cylindrical tactor bodies were printed with diameters of 10 mm and 4 mm, and heights of 10 mm and 5 mm, respectively, incorporating cantilevers ranging from 10 to 40 degrees in angle. Solenoids were constructed by wrapping cured bodies with 100 to 1000 turns of 50 pm Cu wire. The fabrication process involved rotating the bodies attached to a rotating cylinder as the wire was fed through a tip and moved laterally, returning to the original position at the end of each coaxial layer.

[0088] The sensor was mechanically compressed by a texture analyzer, and the corresponding force, current through the system, and vibration were concurrently measured. The results are depicted in Figure 15 A. Three distinct compression levels were applied, (i) resulting in forces of ~ 3.7, - 1.1, and ~ 0.5 N, (ii) yielding currents of ~ 10, ~ 6.3, and ~ 3.0 mA, respectively. Correspondingly, (iii) the vibration strengths are measured at ~ 8.04 m / s2, 5.08 m / s2, and 3.54 m / s2. An iterative decrease in pressure on the CNT sensor results in a proportional decrease in current, subsequently leading to a decrease in vibration strength.

[0089] Example 3. Tuning Resonant Frequencies of Tactors for Frequency-Dependent Vibration

[0090] To deliver frequency dependent vibration to human skin, this Example shows a tactor customization technique capable of tuning the resonant frequency (R) of the tactors. Figures 16A-16E compare experimental vibration acceleration as a function of driving frequency for a commercially available tactor and four tactors consistent with Figure 13 geometry but varying in cantilever angle 0 (10, 20°, 30°, and 40°) across a driving frequency range of 10-1600 Hz. Insets depict the 3D-printed bodies with cantilevers ranging from 10° to 40°, with a magnet attached beneath. Scale bars = 5 mm. The x-axis units and scale is identical across all of Figures 16A- 16E. Figure 16 A characterizes a tactor with a single fixed resonant frequency, represented by the current market standard, the C2 tactor. While the C2 tactor exhibits an fRof - 300 Hz with a magnitude of - 10.3 ± 0.4 m / s2, its effectiveness diminishes below - 200 Hz and decreases in efficacy at higher frequencies. Hence, a platform for developing tactors with a broader range of strong penetrative vibrations at more than a single fRis desirable.

[0091] For exemplary tactors as presented graphically in Figure 13, the cantilevers that the magnet is adhered to each have a different spring constant and should each have different resonance peaks due to this changing oscillatory behavior. For purposes of the Example, four tactors were produced consistent with Figures 3A-4B and tested with cantilevers of increasing angles (0): 10°, 20°, 30°, and 40°. Three tactors of each cantilever support size were printed, wrapped, and subjected to vibration frequencies ranging from ~ 10 to ~ 1600 Hz, while measuring the vibration z- acceleration. Tactors were constrained as they would be to the body. To corroborate the experimental findings, the body, cantilever, and magnet underwent harmonic mode simulation via finite element analysis (FEA).

[0092] The 10° cantilever depicted in Figure 16B displayed a narrow peak at ~ 100 Hz with a maximum acceleration of - 7.56 ± 0.5 m / s2and a near zero amplitude beyond - 600 Hz. Corresponding FEA simulation results revealed a z-axis vibration resonance mode at ~ 132 Hz, with a displacement of ~ 1.92 mm. The displacement in the simulated results gives information about the amplitude of oscillation but does not consider surface interaction. The magnet, on a user, would vibrate against glabrous skin and penetrate to a depth not reflected by the FEA. The 20° cantilever, as shown in Figure 16C, exhibited a smaller acceleration amplitude of ~ 5.31 ± 0.4 m / s2centered at - 250 Hz. FEA simulation data closely matched, indicating a resonance mode at ~ 218 Hz with a displacement of ~ 1.18 mm. In Figure 16D, the 30° cantilever displayed a peak at - 325 Hz, broadened, and reduced in displacement to - 4.68 ± 0.4 m / s2. Simulation results for the 30° cantilever demonstrated a resonance mode at ~ 378 Hz with a displacement of - 0.871 mm. Lastly, the frequency sweep of the 40° cantilever in Figure 16E showcased a broad peak centered at - 425 Hz, with the smallest amplitude of - 3.62 ± 0.3 m / s2. Corresponding simulation data aligned closely, indicating a resonance of - 422 Hz with a displacement of - 0.422 mm.

[0093] Several trends emerge from this data, providing insights into effective tactor design. Primarily, the resonance peak (fR) shifts noticeably towards higher frequencies with increasing cantilever angle (0), correlating with an expected increase in spring constants. This trend is further corroborated by FEA, where larger cantilever sizes exhibit higher resonant frequencies. The larger acceleration observed in the 10° cantilever suggests a stronger vibration force due to its smaller spring constant (E), as evidenced by the simulated displacement decreasing notably with increasing 0. Additionally, there is a clear trend of the resonant peak broadening significantly as the 0 increases. Although the 10° cantilever offers the largest amplitude (displacement) at resonance, it becomes less effective compared to other designs beyond ~ 200 Hz. These findings are noteworthy, considering the demonstration of only four example shapes at a specific body size. To 3D print cantilever angles below ~ 10°, of a differently shaped body, or with different material, would inevitably change the operating resonance peaks.

[0094] Some embodiments of the present invention may be a system, a device, a method, and / or a computer program product. A system, device, or computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention, e.g., processes or parts of processes or a combination of processes described herein.

[0095] The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

[0096] Processes described herein, or steps thereof, may be embodied in computer readable program instructions which may be paired with or downloaded to respective computing / processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and / or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each computing / processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing / processing device.

[0097] Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Java, Python, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention.

[0098] Aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer readable program instructions and in various combinations.

[0099] These computer readable program instructions may be provided to one or more processors of one or more general purpose computers, special purpose computers, or other programmable data processing apparatuses to produce a machine or system, such that the instructions, which execute via the processor(s) of the computer or other programmable data processing apparatus, create means for implementing the function s / acts specified in the flowchart and / or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and / or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function / act specified in the flowchart and / or block diagram block or blocks.

[0100] The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0101] The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flowchart illustration, and combinations of blocks in the block diagrams and / or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

[0102] Where a range of values is provided in this disclosure, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.

[0103] 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 invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, representative illustrative methods and materials are described.

[0104] It is noted that, as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation.

[0105] As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. Any recited method can be carried out in the order of steps recited or in any other order which is logically possible. Alternative methods may combine different elements of specific detailed methods described above and in the figures. While exemplary embodiments of the present invention have been disclosed herein, one skilled in the art will recognize that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A wearable system for generating a somatosensory event-cue feedback loop, comprising one or more flexible sensors configured to convert mechanical pressure into electrical signals; one or more flexible electromagnetic actuators configured to deliver vibratory stimulations that change based on the electrical signals from the one or more flexible sensors; and one or more alternating current (AC) signal generators for powering the one or more flexible electromagnetic actuators.

2. The wearable system of claim 1, wherein the one or more flexible sensors are configured to have an ‘on’ state in which the one or more flexible sensors behave as variable resistors and an ‘off’ state in which the one or more flexible sensors behave as a circuit break.

3. The wearable system of claim 1, wherein at least one sensor of the one or more flexible sensors comprises a first carbon nanotube (CNT)-elastomer composite layer; a second CNT-elastomer composite layer; and an insulating divider separating the first and second CNT-elastomer composite layers.

4. The wearable system of claim 1, wherein at least one actuator of the one or more flexible electromagnetic actuators comprises a flexible solenoid; a magnet; and a flexible support to which the magnet is affixed and which is configured to permit but limit displacement of the magnet relative to the flexible solenoid.

5. The wearable system of claim 4, wherein the flexible solenoid comprises wire wound about a flexible body.

6. The wearable system of claim 5, wherein the flexible body comprises silicone walls.

7. The wearable system of claim 4, wherein the at least one actuator has a diameter of 4-10 mm.

8. The wearable system of claim 4, wherein the flexible support is configured as a pair of cantilevers.

9. The wearable system of claim 1, wherein the one or more flexible electromagnetic actuators have a spectrum of driving frequencies.

10. The wearable system of claim 9, wherein the one or more flexible electromagnetic actuators collectively have resonant peaks spanning at least 100-425 Hz.

11. The wearable system of claim 1, wherein the one or more flexible sensors are wirelessly linked to the one or more flexible electromagnetic actuators.

12. The wearable system of claim 1, wherein the electrical signals induce vibration under any non-zero pressure, pressure above a threshold, or a difference in pressure between at least two of the one or more flexible sensors.

13. The wearable system of claim 1, further comprising a prosthetic socket in which the sensors are arranged to sense weight loading from a residual limb in a state of use.

14. The wearable system of claim 1, further comprising an insole with the one or more flexible sensors arranged to detect plantar pressure on the insole in a state of use.

15. The wearable system of claim 1, further comprising a first glove configured for pressure sensing during gripping using the one or more flexible sensors.

16. The wearable system of claim 15, further comprising a second glove configured to vibrate with the one or more flexible electromagnetic actuators in response to gripping force detected by the first glove.

17. A method of generating a somatosensory event-cue feedback loop, comprising converting pressure caused by forces from gait, grip, or weight loading of a user into electrical signals with one or more flexible sensors; and delivering vibratory stimulations to the user with one or more flexible electromagnetic actuators, the vibratory stimulations changing based on the electrical signals from the one or more flexible sensors.

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