Highly Sensitive, Ultra-Thin Dynamic Lateral Pressure Sensor Using Blue Laser Exposed Porous CNTs

Abstract

Piezoresistive sensor is an essential component of wearable electronics that can detect resistance changes when pressure is applied. An effective approach to enhance its performance is to make micro-structured device. In this paper, porous carbon nanotubes (CNTs) are formed by blue laser (BL) exposure on CNTs layer, which increases its thickness ~4 times compared to the as-deposited layer. Then, the pressure sensor is fabricated by spin coating of styrene-ethylene-butylene-styrene (SEBS) elastomer on the porous CNTs layer. A 1.32 µm thick pressure sensor exhibits a high sensitivity of 6.54 x 106 kPa-1, a wide sensing range of 278 Pa ~ 40 kPa, and fast response/recovery times of 900/760 µs, respectively. The stability of the pressure sensor is demonstrated by repeated loading and unloading of 20 kPa for 3600 cycles. The stretchable pressure sensor was also demonstrated using lateral CNT electrodes on SEBS surface, exhibiting stable pressure performance up to 20% stretching. Finally, a 32 x 32 active-matrix pressure sensor array is demonstrated consisting of amorphous InGaZnO4 thin-film transistor (TFT) backplane for pressure mapping and real-time monitoring. The sensor array demonstrates dynamic area touch by pen writing with ~1 cm/s speed.