Flexible Pressure Sensors Based on Silicon Nanowire Array Built by Metal-Assisted Chemical Etching

Abstract

This letter presents a flexible pressure sensor based on silicon nanowires (Si NWs) built by metal-assisted chemical (MAC) etching. The MAC etched NWs, with a height of $30~\mu \text{m}$ and a diameter as small as 200 nm, were post-treated with polydimethylsiloxane to endow the NW sensor with elasticity and high-pressure resistance. The piezoresistance of the Si NWs varies from ${1.03}\times {10}^{{6}}$ to ${5.3}\times {10}^{{4}}$ ohms as the applied pressure changes from 0 to 4.5 kPa, indicating a resistance change rate of about 94%. The Si NW sensor also exhibits a fast response and recovery time as 0.3 s, it is capable of distinguishing pressure changes as low as 0.3kPa, which is way lower than the perceivable range (10-40kPa) of human skin.