Cutaneous Ionogel Mechanoreceptors for Soft Machines, Physiological Sensing, and Amputee Prostheses

Abstract

Touch sensing has a central role in robotic grasping and emerging human–machine interfaces for robot‐assisted prosthetics. Although advancements in soft conductive polymers have promoted the creation of diverse pressure sensors, these sensors are difficult to be employed as touch skins for robotics and prostheses due to their limited sensitivity, narrow pressure range, and complex structure and fabrication process. Here, a highly sensitive and robust soft touch skin is presented with ultracapacitive sensing that combines ionic hydrogels with commercially available conductive fabrics. Prototypical designs of the capacitive sensors through facile manufacturing methods are introduced and a high sensitivity up to 1.5 kPa−1 (≈44 times higher than conventional parallel‐plate capacitive counterparts), a broad pressure detection range of over four orders of magnitudes (≈35 Pa to 330 kPa), ultrahigh baseline of capacitance, fast response time (≈18 ms), and good repeatability are demonstrated. Ionogel skins composed of an array of cutaneous mechanoreceptors capable of monitoring various physiological signals and shape detection are further developed. The touch skin can be integrated within a soft bionic hand and provide an industrial robot and an amputee with robust tactile feedback when handling delicate objects, illustrating its potential applications in next‐generation human‐in‐the‐loop robotic systems with tactile sensing.

Flexible Electronics and Devices as Human–Machine Interfaces for Medical Robotics

“…In a system, they can work independently, but, ideally, each part can form a closed-loop system that is interlinked to perform more precise and complex tasks. [76,153] Currently, some integrated work can enhance space utilization, [596] reduce manufacturing costs, [155] and achieve in situ information sensing, processing, and actuating simultaneously for more accurate therapy. [546,602] A flexible prosthetic system has a representative flow of information with various integrated components.…”

“…[ 148 ] Compared with passive perception, active sensing refers to amputees detecting unstructured environments with prosthetics subjectively, such as identifying the stiffness and texture of objects, user‐interaction with people, and grasping. [ 155 ] As an example, parallel ridges were fabricated on the surface of a poly(vinylidene difluoride) (PVDF)‐based piezoelectric sensor to detect texture‐induced vibrations. [ 156 ] Furthermore, adding e‐skins on prosthetics creates a closed‐loop sensory feedback control, which allows for a more accurate, facile, and compliant touch and grasp.…”

Wearable Triboelectric Sensors Enabled Gait Analysis and Waist Motion Capture for IoT‐Based Smart Healthcare Applications

“…For instance, a cutaneous mechanoreceptor using capacitive variation was developed for soft machines, physiological sensing, and amputee prostheses, showing its outstanding sensitivity and wide pressure range. [48] Wang et al proposed a multifunctional tactile sensor via a hierarchically patterned structure for multiple stimulus detections. [49] In general, they exhibit advances in accuracy and stability, but some of the aforementioned methods are still restrained by several drawbacks, e.g., resistive sensor usually suffers the temperature drift and the parasitic capacitance affects the sensing result for the capacitive sensor.…”

“…For instance, a cutaneous mechanoreceptor using capacitive variation was developed for soft machines, physiological sensing, and amputee prostheses, showing its outstanding sensitivity and wide pressure range. [ 48 ] Wang et al. proposed a multifunctional tactile sensor via a hierarchically patterned structure for multiple stimulus detections.…”

Tough and Highly Efficient Underwater Self‐Repairing Hydrogels for Soft Electronics

“…[7][8][9] Tough hydrogels have attracted considerable attention in soft electronics owing to their biological tissue-like high-water content, softness, tenacity, and stretchability. [10][11][12][13] Synthetic hydrogels have been designed for self-repair by incorporating dynamic bonds such as H-bonds, [14] Schiff base bonds, [15] metal-ligand coordination, [16] and ionic interactions. [17] However, most of the reported self-repairing hydrogels are unstable under humid conditions, and their mechanical toughness decreases after healing.…”