The silver-coated sponge spacer and multiwalled carbon nanotube-dragon skin electrodes for cushion-type nanocomposite pressure sensor array

Abstract

Prolonged sitting in an unhealthy posture can cause various health ailments. Especially, wheelchair users and office workers suffer from pressure ulcer and chronic back pain. Here we report a cushion-type 20 × 20 pressure sensor array made by the low-cost simple scalable method. The soft electrode is made of multiwalled carbon nanotubes and dragon skin matrix. The resistance of the electrode is dramatically decreased by the insertion of a copper wire. The silver-coated polyurethane sponge provides the piezoresistive sensing mechanism and significantly improves the sensor response. The continuous sensing range (0–70 kPa) is sufficient for sitting posture analysis, and the sensitivity is as high as 0.10 kPa-1 in the range of 0–10 kPa. The signal is processed using a single board microcontroller, and data are transmitted to a mobile device wirelessly. The sequential voltage supply and signal read minimize the number of voltage supply and analog-to-digital conversion ports in the microcontroller, and a modified conductance matrix algorithm is designed to completely eliminate crosstalk effect of the sensor array. The pressure sensor successfully recognizes various sitting postures, including optimal and left/right/forward leaning, and may find immediate rehabilitation and health care applications.