Biobased, degradable and directional porous carboxymethyl chitosan/lignosulfonate sodium aerogel-based piezoresistive pressure sensor with dual-conductive network for human motion detection

The rapid growth of wearable electronics, healthcare monitoring, and human–computer interaction has sparked growing interest in flexible piezoresistive pressure sensors, which in turn raised considerable concerns about the increasingly serious environmental pollution caused by electronic waste. Herein, a radial inward directional freezing-drying method was proposed to prepare biobased, degradable and directional porous carboxymethyl chitosan/lignosulfonate sodium aerogel with dual-conductive network constructed by carboxylated multiwalled carbon nanotubes (C-CNTs) and MXene for piezoresistive pressure sensor. Owing to the synergistic conductive network of C-CNTs and MXene as well as directional porous structure, the sensor exhibited high sensitivity (2.33 kPa−1 in 0–10 kPa, 1.04 kPa−1 in 10–31 kPa, 0.53 kPa−1 in 31–53 kPa), fast response (response/recovery time of 140/60 ms), and excellent repeatability (2,000 loading–unloading cycles). Moreover, the sensor was successfully applied for human motion detection, healthy monitoring, micro-expression identification, and speech recognition. In addition, the aerogel for sensor was able to be completely degraded within 70 h in 1 M hydrochloric acid solution or partially degraded in boiling water within 2.5 h for the recycling of conductive materials, which was beneficial for not only environment protection but also saving resource. Our findings conceivably stand out as a new strategy to prepare environmentally friendly and high-performance piezoresistive pressure sensor and will promote the further development and application of flexible electronics.