Patchable thin-film strain gauges based on pentacene transistors

We present a patchable thin-film strain gauge for which output current responds sensitively to external strain. For this work, integrated organic thin-film transistors using pentacene as an active component were fabricated on a freestanding polyurethaneacrylate film with high flexibility and adhesive properties providing patchability. The device can be easily mounted onto non-flat surfaces, and the output characteristics show a strong correlation with the structural strain of freestanding polymeric film, which allows the external strain applied to the device to be gauged. In addition, a surface shape can be detected after mounting the device onto a non-flat surface, and the thickness of a complex structure can be inversely calculated using a calibration curve. It is anticipated that these results will be applied to the development of various patchable sensors and thickness measurement systems, which can lead to further applications. (C) 2015 Elsevier B.V. All rights reserved.