Full printed flexible pressure sensor based on microcapsule controllable structure and composite dielectrics

Abstract

Flexible pressure sensors have attracted a great deal of attention due to their significant potential for applications in electronic skins, artificial intelligence and wearable health care devices. It is still challenging to obtain the flexible pressure sensor with high sensitivity and large linear measuring range in a low cost and facile way. In this paper, the composite dielectrics ink based on thermal expansion microcapsules (TEMs), silver nanowires (Ag NWs) and polydimethylsiloxane was employed to improve the performance of the flexible capacitive pressure sensor. The screen printing method was used to prepare the electrodes and microstructural composite dielectric layer. The results indicated that the flexible sensor with composite dielectrics of 1 wt.% TEMs and 0.5 wt.% Ag NWs demonstrated the excellent performance including the maximum sensitivity of 2.1 kPa−1 and wide linear pressure range. The dramatic improvement in the sensor’s sensitivity and linear pressure range could be attributed to the synergetic effects of the TEMs controllable microstructure and relative permittivity increase of composite dielectrics under pressure. In addition, the full printed flexible pressure sensor showed its limit of detection of 1.3 Pa, responding time of 50 ms, proximity sensing distance of 24 cm and good mechanical durability over 3600 cyclic compress–release testing. To our best knowledge, these characteristics are superior to the printed capacitive flexible sensor in reporting. In this paper, the full printed flexible pressure sensor demonstrates it is a good candidate to be applied in the field of E-skin, pressure mapping and wearable health care devices, etc.