Highly Morphology‐Controllable and Highly Sensitive Capacitive Tactile Sensor Based on Epidermis‐Dermis‐Inspired Interlocked Asymmetric‐Nanocone Arrays for Detection of Tiny Pressure

Abstract

The tactile sensor lies at the heart of electronic skin and is of great importance in the development of flexible electronic devices. To date, it still remains a critical challenge to develop a large-scale capacitive tactile sensor with high sensitivity and controllable morphology in an economical way. Inspired by the interlocked microridges between the epidermis and dermis, herein, a highly sensitive capacitive tactile sensor by creating interlocked asymmetric-nanocones in poly(vinylidenefluorideco-trifluoroethylene) film is proposed. Particularly, a facile method based on cone-shaped nanoporous anodized aluminum oxide templates is proposed to cost-effectively fabricate the highly ordered nanocones in a controllable manner and on a large scale. Finite-element analysis reveals that under vertical forces, the strain/stress can be highly strengthened and localized at the contact apexes, resulting in an amplified variation of film permittivity and thickness. Benefiting from this, the developed tactile sensor presents several conspicuous features, including the maximum sensitivity (6.583 kPa −1 ) in the low pressure region (0-100 Pa), ultralow detection limit (≈3 Pa), rapid response/recovery time (48/36 ms), excellent stability and reproducibility (10 000 cycles). These salient merits enable the sensor to be successfully applied in a variety of applications including sign language gesture detection, spatial pressure mapping, Braille recognition, and physiological signal monitoring. Keywords anodized aluminum oxide, capacitive tactile sensors, electronic skin, highly morphology-controllable, interlocked asymmetric-nanocone arrays, P(VDF-TrFE)

Recent Progress in Flexible Pressure Sensors Based Electronic Skin

“…The presence of microstructures results in a fast response and high sensitivity (Figure 4h). [107] Microstructures expand the air gap between the electrodes, and the dielectric layer is highly influenced by deformation. For instance, Wu et al reported all-fabric with a wireless battery-free monitoring system; the capacitance pressure sensor shows a high sensitivity of 0.283 KPa À1 .…”

Multifunctional Electronic Skin With a Stack of Temperature and Pressure Sensor Arrays

“…To enhance the sensitivity, researchers have explored various solutions such as using micro pillars, microcones, micro pyramid, micro cones, and/or bionic patterns etc. [25][26][27][28][29][30]. These approaches have yielded interesting results but understanding the role of dielectric material properties such as their stiffness is also an important factor that is needed to be explored to reproduce the mechanoreceptors sensing capability [16].…”

First Decade of Interfacial Iontronic Sensing: From Droplet Sensors to Artificial Skins

“…Sensing technology has experienced a rapid growth, by extending the power of natural senses, over the past decades. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In particular, measurements of external mechanical force or pressure at a surface, inspired by human sense of touch, have already been employed in a wide range of industrial, medical, and consumer applications. Historically, this category of the sensing devices has been called a pressure sensor when gauging into fluidic objects (either liquid or air), or force sensors in contact with solid objects.…”