Multifunctional Flexible Pressure Sensor Based on a Cellulose Fiber-Derived Hierarchical Carbon Aerogel

Flexible pressure sensors have attracted widespread attention in recent years due to their potential applications for health monitoring and human–machine interfaces. However, the fabrication of environmentally friendly and well-performing pressure sensors using biobased materials remains a great challenge. Herein, a compressible carbon aerogel was prepared by sequential microfibrillation, periodate oxidization, and tannic acid (TA) cross-linking of cellulose fibers (CFs) followed by freeze-drying the as-prepared CF suspension and high-temperature pyrolysis of the obtained CF aerogel. The microfibrillation endows the carbon aerogel with a hierarchical structure, which improves the bonding strength and compressibility of the carbon aerogel. Periodate oxidation and TA cross-linking improved the mechanical properties of the carbon aerogel, while pyrolysis endowed the carbon aerogel with excellent conductivity, enabling the carbon aerogel to be a good pressure-sensing material. When assembled into a pressure sensor, the sensor shows a high sensitivity of 4 kPa –1, a fast response/recovery time of 32/30 ms, a low-pressure detection limit of 0.8 Pa, and good stability and excellent reproducibility (3000 cycles at 0.5 kPa). Moreover, the pressure sensor can be used to accurately monitor various human activities and also spatially resolve pressure variations when integrated into a sensor array. The pressure sensor also responds linearly to increased temperature and humidity. These results suggest that this hierarchical carbon aerogel-based pressure sensor has great potential for application as a multifunctional sensor.