Finite bending of a stretchable thin-film transistor

This paper presents the effects of the structural variations in organic thin-film transistors (OTFTs) with an elastomeric substrate subjected to a finite bending on the capacitances between the source/drain and gate electrodes and the field-effect mobilities. We model the OTFT as a bilayer using an incompressible neo-Hookean material. Based on the assumption that the channel width is significantly larger than the channel length, we derive the relative changes in the capacitances and mobilities of the modeled bilayer OTFTs during deformation. The theory of finite bending predicts the discrepancy compared with the theory of infinitesimal bending, when the bending strain and stiffness ratio are increased for outward bending. The results reveal that there exists an optimal combination of the thickness and stiffness ratio for minimizing the strain at the top and bottom surfaces of the bilayer. Our analysis provides a basis for the structural design of stretchable devices using organic materials.