Characterization of the spatial elastoresistivity of inkjet-printed carbon nanotube thin films for strain-state sensing

Carbon nanotube (CNT)-embedded polymer solution can be inkjet-printed into a thin sheet consisting uniform morphology and consistent electrical properties. When subjected to a loading scheme, the thin film's inherent electrical property changes in tandem with the deformation. This unique property makes CNT thin films the appropriate candidate for strain sensing applications. Recent studies on characterizing the gage factor of CNT-embedded thin films are limited to learning the materials resistance change along the loading direction only. However, research interests on strain measurement of a structure have shifted from point-based interrogation to spatial strain-state monitoring. In this study an attempt to characterize its anisotropic resistivity was carried out. The resistivity-strain constitutional relation of an inkjet-printed CNT thin film is established based on theories for semi-conductive materials. The 2D elastoresistivity properties were characterized via the Montgomery method. It is observed that the change in resistivity in both directions are exhibiting linear trend to their strains in the same direction, but the thin film is more sensitive toward compressive strains. The final result of this study has inspired future research on fully characterizing the thin film's elastoresistivity under different loading situations, and the way to characterize shear elastoresistivity shall also be reconsidered.