Microstructured flexible capacitive sensor with high sensitivity based on carbon fiber-filled conductive silicon rubber

Flexible sensors with high sensitivity and stability have been tremendously attractive in recent years. In this study, flexible capacitive sensors (FCSs) with microstructured-surface were fabricated, where electrode layers (e-layers) and dielectric layers (d-layers) of the FCSs were sprayed with carbon fiber (CF) filled-polydimethylsiloxane (PDMS) and pure PDMS on substrate with surface roughness, respectively. Sensitivity of the fabricated FCSs to compressive load was evaluated. Influence of the surface microstructure of D- and e-layers on the sensitivity was studied through in-situ microscopic observations and theoretical capacitance calculations. Results showed that the roughness of the surface microstructure did have a correlation with the sensitivity. Excellent sensing performance, including a high sensitivity (∼0.82 kPa⁻¹), ultrafast response (∼0.2 s) and relaxation (∼0.3 s) time, ultralow detection limit (∼1.2 Pa), and excellent stability (10⁴ loading/unloading cycles) over a wide pressure range (0−50 kPa) appeared on the FCS with its surface microstructure size of 48.6 μm in roughness. The high sensitivity of the fabricated FCS was dominantly resulted from the closing of air gap between e- and D-layers. A 3 × 3 FCS array capable of distinguishing space pressure distribution and a mouse glove capable of inputting computer information were finally fabricated which demonstrated a prospect of the FCS in micro-load response and human-machine interaction applications.