Ultrasensitive Strain Gauges Enabled by Graphene-Stabilized Silicone Emulsions

Here, an approach is presented to incorporate graphene nanosheets into a silicone rubber matrix via solid stabilization of oil-in-water emulsions. These emulsions can be cured into discrete, graphene-coated silicone balls or continuous, elastomeric films by controlling the degree of coalescence. The electromechanical properties of the resulting composites as a function of interdiffusion time and graphene loading level are characterized. With conductivities approaching 1 S m⁻¹, elongation to break up to 160%, and a gauge factor of ≈20 in the low-strain linear regime, small strains such as pulse can be accurately measured. At higher strains, the electromechanical response exhibits a robust exponential dependence, allowing accurate readout for higher strain movements such as chest motion and joint bending. The exponential gauge factor is found to be ≈20, independent of loading level and valid up to 80% strain; this consistent performance is due to the emulsion-templated microstructure of the composites. The robust behavior may facilitate high-strain sensing in the nonlinear regime using nanocomposites, where relative resistance change values in excess of 10⁷ enable highly accurate bodily motion monitoring.