Electromechanical properties of reduced graphene oxide thin film on 3D elastomeric substrate

Electrically conducting, 3D elastomeric composite foams are fabricated successfully using multiple cycles of infusing polyurethane foams with graphene oxide sheets followed by reduction, to form coatings of reduced graphene oxide up to ∼1260 nm thick. The reduced graphene oxide coating increases the compression modulus of the composite and lowers the electrical resistance significantly compared with polyurethane foam, the extents of which increase with increasing coating thickness. The electrical resistance of the coated foams varies by as much as three orders of magnitude for coating thickness between ∼150 and ∼1200 nm, whereas the capacitance varies by one order of magnitude. Both the stress-strain and the resistance-strain behavior are highly repeatable with compression cycles performed up to 70% strain. Both SEM and X-ray tomography characterization show that deformation is mostly through bending of the pore walls up to about 20% strain, collapse of pore openings to about 60% strain, and densification beyond that. Micro-fractures also develop on the coating during the first few cycles of compression, but no obvious structural changes can be detected afterwards.