Yu-Wen Chen, Ying-Hung Chen, Ping-Yen Hsieh, Ju-Liang He, Feng Chia University, Taichung City, Taiwan
For solving the issues of precision and sensitivity of strain gauge sensors, more stable senser materials with respect to their servicing environments are needed, Constantan alloy for instance, a copper-nickel alloy, is widely used for its good ductility, antimagnetic, low temperature coefficient of resistance (TCR) as well as corrosion resistance, allowing it to be stable over a wide range of servicing environment. On the other hand, the commonly used rigid substrates for thin-film strain gauge, polyimide for example, is high elastic modulus that deviates the result from the intrinsic stress-strain behavior of the measured sample, not to mention the low sensitivity brought by its rigidity.
With these considerations, a soft (thus low elastic modulus) and stretchable substrate, PDMS in this regard, was used to deposit Constantan alloy thin film by using high power impulse magnetron sputter (HIPIMS) to construct a stretchable thin-film strain gauge. It is anticipated that such a sensor shall bring high precision and sensitivity. For these reasons, HiPIMS deposition to obtain a stable and strongly adhered Constantan alloy conductive thin film with characterization and analysis by using SEM and XRD were carried out. Meander-shaped Constantan thin films were patterned for electrical resistance control by using laser scribing. The obtained gauges were measured their repeated stress-strain behavior for performance evaluation, and ultimately meet the required standards for precision strain gauge sensing applications.