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.