Carbon-based aerogel in three-dimensional polyurethane scaffold: the effect of in situ unidirectional aerogel growth on piezoresistive properties

Carbon-based aerogels (CA) with durable piezoresistive properties possess great promise for applications in wearable electronics. However, it is still a great challenge to fabricate high performance aerogel sensors due to the limits of mechanical properties. We recently developed a novel strategy to build aerogel/foam hybrid structure that can effectively enhance the mechanical properties of aerogel-based sensors. Herein, CA/polyurethane foam (PUF) composite was fabricated via in situ unidirectional freeze-drying process starting from a carbon nanotubes (CNTs)/graphene oxide (GO) aqueous dispersion stabilized with chitosan (CS) which was filled into the porosity of an open cell PUF. The resulting composite shows a microscopic anisotropy in the CA with electrical conductivity as high as 10.54 S m-1. The piezoresistive sensitivity of the resulting composite can be simply modulated over a wide range from 1.1 to 3.6 by adequately selecting its initial pre-strain. The CA/PUF composite exhibits excellent compressible resilience at the strain of 50% for at least 100 cycles. In addition, the sensor was successfully applied for detecting various human motions. These unique properties make the realized composite a promising candidate for effective flexible piezoresistive strain sensors in wearable applications.