Abstract
The fascinating human somatosensory system with its complex structure is composed of numerous sensory receptors possessing distinct responsiveness to stimuli. It is a continuous source of inspiration for tactile sensors that mimic its functions. However, to achieve single stimulus-responsiveness with mechanical decoupling is particularly challenging in the light of structural design and has not been fully addressed to date. Here we propose a novel structural design inspired by combining the characteristics of electronic skin (e-skin) and electronic textile (e-textile) into a hybrid interface to achieve a stretchable single stimuli-responsive tactile sensor. The stencil printable biocarbon composite/silver-plated nylon hybrid interface possesses an extraordinary resistance switching (ΔR/R0 up to ∼104) under compressive stress which is controllable by the composite film-thickness. It achieves a very high normal pressure sensitivity (up to 60.8 kPa–1) in a wide dynamic range (up to ∼50 kPa) in the piezoresistive operation mode and can effectively decouple stresses induced by stretching or bending. In addition, the device is capable of high accuracy strain sensing in its capacitive operation mode through dimensional change dominant response. Because of these intriguing features, it has potential for the next-generation Internet of Things devices and user-interactive systems capable of providing visual feedback and more advanced robotics or even prosthetics.
Highlights
We propose a novel structural design inspired by combining the characteristics of e-skin and electronic textile (e-textile) into a hybrid interface consisting of biocarbon composite/silver-plated nylon
The BC/SPN device resembles a typical parallel-plate capacitor structure having two overlapped electrodes in the form of silver-plated nylon (SPN) and a thin dielectric layer made of biocarbon composite (BC)
The BC/SPN was fabricated by stencil printing two layers of the composite solutions onto polyimide taped SPN and applying pressure after stacking the top SPN onto a planar structure (SI Section 1.1 and Figure S2)
Summary
Mimicking the human somatosensory system has been the source of inspiration for tactile sensors having the capability of transducing physical and environmental stimuli into electrical signals.[1−5] Human skin has fascinating sensing capabilities through its numerous sensory receptors located on the top layers of the dermis and epidermis which have different rates of adaptability, receptive field sizes, and responsiveness to stimuli.[4,6] The complex sensory systems enable precise physical interaction with the environment through the perception of touch, surface roughness, slippage, position, and motion.[1,4,6]Even though surpassing the subtle sensing capabilities of human skin has proven to be a serious challenge, the efforts have paved the way for the next-generation of robotics, advanced prosthetics, healthcare, and medical devices.[4−9]Recent research on mimicking the tactile sensation of human skin with capacitive,[10−15] resistive,[5,16−22] and other sensing mechanisms[23−26] has focused on achieving a high sensitivity over the full transducer range of human skin,[17,26−30] enabling the detection of normal and shear forces[6,31] and even accurate measurement of a single-stimulus under dynamic deformations on curvilinear surfaces.[7,17,31] Structural design is one of the most important aspects to achieve high performance for electronic skins (e-skins). ACS Applied Materials & Interfaces www.acsami.org taken advantage of hierarchical structures inspired by nature,[12,28,30] microstructured materials (such as micropyramids, microgrooves, microdomes),[6,9,26,27,29] channels[17] and even hollow/porous[32,33] structures, that allow control of the contact area and localized stress concentrations.[29,34−36] Other efforts have focused on material development, such as creating supercapacitive iontronic sensing with an exceptionally high unit-area capacitance aiming toward excellent sensing capabilities.[37,38] Yet there still exist only a few pressure sensors that can maintain a high sensitivity of >50 kPa−1 in the medium pressure regime (up to 100 kPa), capable of more closely mimicking the tactile sensing capabilities of natural skin.[5,23,26,31]
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