Experimental determination of the compressive piezoresistive response of a free-standing film with application to reduced graphene oxide.

Piezoresistance, the change of electrical resistance due to applied mechanical strain, has been characterized for films in tension or bending. However, measuring the compressive piezoresistance of films remains a challenge because the in-plane compression often results in macroscopic buckling and kinking, leading to localization of strain. Here, we overcame this issue via a newly developed method to calculate the compressive piezoresistance of films by measuring the change of resistance in situ under tensile and bending stresses. A linear fit was applied to the experimental tensile piezoresistive response and a quadratic fit was applied to the bending piezoresistive response. The experimental bending response was mathematically decomposed into its tensile and compressive components. The compressive response was then isolated by subtracting the tensile response from the bending response. In this study, the method is applied to reduced graphene oxide (rGO) film specimens. For rGO films, the compressive piezoresistance was found to be much greater than the tensile piezoresistance. Scanning electron microscope images revealed that extensive damage occurred on the compressive side of the bending specimen, resulting in a large increase in resistivity. We anticipate that our study will be adapted to applications that require mechanically reliable, flexible, and highly conductive materials, such as flexible electronics and structural energy and power. [ABSTRACT FROM AUTHOR]