Structuring the reduced graphene oxide/polyHIPE foam for piezoresistive sensing via emulsion-templated polymerization

Abstract

Flexible conductive polymer composite foams are promising materials as piezoresistive sensors. Unfortunately, the common solid-templated fabrication method is limited by the scarcity of template structure, which hinders the improvement of sensing performance through rational design of the pore structure. Herein, a series of graphene oxide (GO)-based flexible conductive foams with unimodal and broad pore size distribution, and hierarchically porous structure were fabricated through high-internal-phase emulsions (HIPEs) as liquid templates. The pores were structured by tuning the droplet size distribution of HIPEs, which were regulated by changing the pH and GO loadings. The pore structure had great effect on the mechanical, electrical, and piezoresistive properties of the developed foams. Compared to foams with either unimodal or broad pore size distribution, the hierarchically structured foams exhibited more than 50% increase in Young’s modulus, more than 30% improvement in pressure sensitivity, and broadened pressure responsive ranges up to more than 200 kPa.