Temperature-insensitive conductive composites for noninterference strain sensing

Very few thin-film strain gauges (TFSGs) that exhibit temperature self-compensation have been developed. Their temperature insensitivity range is typically < 100 °C, and they cannot be used for static strain sensing in variable-temperature environments. In this study, environmental interference owing to temperature fluctuations was successfully eliminated by controlling electron scattering and thermally assisted hopping transport in conductive composites. A new temperature-insensitive material was developed. The proposed strategy enables noninterference dynamic strain monitoring over an ultrawide temperature range of 30–300 °C, which is approximately 200 °C higher than that of noninterference TFSGs that have been reported. In particular, we propose the smallest feature unit of electron transport in conducting composites, that is, the pathway of an electron through a conductive particle and adjacent junction. This unit retains all the features of the entire conductive network, such as the temperature-resistivity effect, and is the smallest unit that can fully reflect the electron transport behavior. We manipulated the microstructure such that the static strain affects only the arrangement and number of temperature-insensitive feature units without destroying its internal structure, enabling temperature independence under static strain. The first noninterference TFSG was designed with a gauge factor of > 2300 for static strain sensing. The thermal output strain error at 30–200 °C was < 0.0016%.