3D Dielectric Layer Enabled Highly Sensitive Capacitive Pressure Sensors for Wearable Electronics

Abstract

Flexible capacitance sensors play a key role in wearable devices, soft robots, and the Internet of things (IoT). To realize these feasible applications, subtle pressure detection under various conditions is required, and it is often limited by low sensitivity. Herein, we demonstrate a capacitive touch sensor with excellent sensing capabilities enabled by a three-dimensional (3D) network dielectric layer, combining a natural viscoelastic property material of thermoplastic polyurethane (TPU) nanofibers wrapped with electrically conductive materials of Ag nanowires (AgNWs). Taking advantage of the large deformation and the increase of effective permittivity under the action of compression force, the device has the characteristics of high sensitivity, fast response time, and low detection limit. The enhanced sensing mechanism of the 3D structures and the conductive filler have been discussed in detail. These superior functions enable us to monitor a variety of subtle pressure changes (pulse, airflow, and Morse code). By detecting the pressure of fingers, a smart piano glove integrated with 10 circuits of finger joints is made, which realizes the real-time performance of the piano and provides the possibility for the application of intelligent wearable electronic products such as virtual reality and human–machine interface in the future.

Flexible and Stretchable Capacitive Sensors with Different Microstructures

“…[36] By adding a small microstructure in the PDMS dielectric layer, the pressure sensitivity was increased by more than 30 times compared with an unstructured PDMS layer of the same size. There are two main reasons for the significant increase in sensitivity: i) the presence of many voids in the microstructure film is conducive to a smaller elastic modulus and can provide a larger deformation space under the applied pressure, which means that the distance between two electrodes can change more to further increase ΔC under the same pressure; [36,41,78,94,95] ii) the dielectric constant of the polymer matrix (e.g., k PDMS ≈ 3.0) is higher than that of air (≈1). [36,62] When compression occurs, the air volume is occupied by the matrix, and ΔC increases accordingly.…”

Microstructured capacitive sensor with broad detection range and long-term stability for human activity detection

“…To date, researchers have made lots of efforts to improve the comprehensive performance of the capacitive sensor in various aspects, such as sensitivity, detection limit/range, response time, and stability 12,[22][23][24] . For example, introducing the microstructure has been regarded as one of the effective strategies for remarkably improving the sensor sensitivity due to the distinct deformation of the microstructure and the subsequent increase in the capacitance variation.…”

Natural bamboo leaves as dielectric layers for flexible capacitive pressure sensors with adjustable sensitivity and a broad detection range

“…[1][2][3][4][5][6][7][8][9] Capacitive pressure sensors (CPSs), which are generally considered as a parallel plate capacitor consisting of a top/bottom electrode and a dielectric layer, have become an attractive type of FWS due to their advantages of simple structure fabrication, low power consumption, negligible temperature uctuation, fast response, and excellent stability. [10][11][12][13][14] However, the low sensitivity and narrow detection range are still limiting the overall performance and further applications of CPSs. [15][16][17] The sensing function of the capacitive sensor in response to the external stimuli is realized by monitoring the capacitance changes.…”