Piezoresistive and Mechanical Characteristics of Graphene Foam Nanocomposites

We report the piezoresistive and mechanical characteristics of three-dimensional (3D) graphene foam (GF)–polydimethylsiloxane (PDMS) nanocomposites processed by a facile two-step approach. A polyurethane (PU) foam with graphene embedded (and aligned) in the pore walls is pyrolyzed and then impregnated with PDMS to form a GF–PDMS nanocomposite, resulting in a slitlike network of graphene embedded in the viscoelastic PDMS matrix. The interconnected graphene network not only imparts excellent electrical conductivity (up to 2.85 S m –1, the conductivity of PDMS is 0.25 × 10 –13 S m –1 ) to the composite but also enables ultrasensitive piezoresistive behavior. For an applied compressive strain of 10% we report a 99.94% reduction in resistance, with an initial gauge factor of 178, and note that this value is significantly higher than those reported in the literature. Cyclic compression–release tests conducted at different strain amplitudes demonstrate that both the mechanical and piezoresistive responses of the GF–PDMS are fully reversible up to a maximum strain amplitude of 30%. The facile processing, recoverable, and reversible response over 1000 cycles, good hysteresis performance over a range of strain rates, and energy absorption characteristics open new opportunities for GF–PDMS nanocomposites in various applications such as soft robots and human–machine interface technologies.