Flexible Waterborne Polyurethane/Cellulose Nanocrystal Composite Aerogels by Integrating Graphene and Carbon Nanotubes for a Highly Sensitive Pressure Sensor

Abstract

Flexible piezoresistive sensors with high sensitivity, low cost, and wide response ranges are urgently required due to the rapid development of wearable electronics. Here, carbon nanotubes (CNTs)/graphene/waterborne polyurethane (WPU)/cellulose nanocrystal (CNC) composite aerogels (CNTs/graphene/WC) were fabricated by facile solution mixing and freeze-drying technology for high-performance pressure sensors. WPU and CNC were constructed as a 3D structure skeleton, and the synergistic effect of CNTs and graphene was beneficial to enhancing the sensing performance. The obtained pressure sensor exhibits a highly porous network structure, remarkable mechanical properties (76.16 kPa), high sensitivity (0.25 kPa–1), an ultralow detection limit (0.112 kPa), and high stability (>800 cycles). More importantly, the piezoresistive sensor could be successfully used to detect various human motions such as finger bending, squatting–rising, walking, and running and effectively extract real-time information by the electrical signals. In addition, the CNTs/graphene/WC composite aerogel exhibits excellent thermal insulation performance, which can withstand 160 °C for a long time without any damage to the structure. The CNTs/graphene/WC composite aerogel, because of its thermal insulation property, endows the sensor with the potential for application in high-temperature environments. The results indicate that CNTs/graphene/WC composite aerogels possess high sensing performance and outstanding thermal insulation, which means that the aerogels could be used as flexible, wearable electronics.