A Novel Graphene Foam for Low and High Strains and Pressure Sensing Applications

We are reporting the formation of free-standing graphene foam (GF) via a novel two-step process, in which a polyurethane (PU) foam is first dip-coated with graphene oxide (GO) and subsequently the dried GO-coated-PU is heated in nitrogen atmosphere at 1000°C. During the pyrolysis of the GO-coated-PU, GO is reduced to GF whereas PU is simultaneously decomposed and released completely as volatiles in a step wise mass-loss mechanism. Morphology of the formed GF conforms to that of the pure PU foam as indicated by the scanning electronic micrographs. Polydimethylsiloxane (PDMS) was successfully infiltrated inside the GF to form flexible and stretch-able conductors. The GF-PDMS composite was tested for it's pressure and strain sensing capabilities. It is shown that a 30% compressive strain changes resistance of the GF-PDMS composite to about 800% of it's original value. Since density of the formed GF is tunable, therefore, the pressure/strain sensivity of the GF-PDMS composite is also tunable.