Fabrication of stretchable 3D graphene foam/poly-dimethylsiloxane composites for strain sensing

In this work, we present the fabrication of a 3D graphene and polydimethylsiloxane (PDMS) composite for strain sensing applications. A three-dimensional (3D) graphene foam (GF) was synthesized by chemical vapor deposition (CVD) with nickel foam as a template. GF/PDMS composite was then formed by dip coating the graphene foam into PDMS solution and the nickel template was removed by etching in a hot hydrochloric acid. The ratio of PDMS and curing agent was varied to obtain the optimum condition for high conductivity and flexibility. The results from SEM showed that the composite of graphene foam with high PDMS:curing agent ratio provided more pores in the composite structure. The mechanical test demonstrates that the flexibility of optimal GF/PDMS composite with higher PDMS:curing agent ratio was higher than those prepared with other curing agent contents. The electrical resistance change of the GF/PDMS composite as a function of applied strain was studied. In addition, the resistance of the composite increased with increasing applied strain until the break at the strain of 15%, 21%, 23% and 83% for the composite with PDMS/curing agent ratios of 5:1, 10:1 and 15:1, and 20:1 respectively, respectively. The studied of electrical properties of the GF/PDMS composite under bending stress showed that the resistance of the GF/PDMS composite decreased considerably with increasing bending curvature and can be fully recovered after straightening. Therefore, GF/PDMS composites can be potentially to be used as a flexible strain sensor.