A kirigami-based Parylene C stretch sensor

We present the first slotted Parylene C kirigami device for transducing stretch-induced displacement under multiple modes of operation. Devices consist of thin-film gold traces wound among multiple rows of offset slits etched through a free-film Parylene substrate. Slits were etched via a switched-chemistry DRIE in oxygen plasma, resulting in densely packed slit designs. Multiple slit designs were evaluated and devices with more tightly packed slits were found endure greater stretch distance before failure, with devices containing more tightly packed slits able to stretch up to 9 mm (180%) without plastic deformation or compromise of electrical integrity. Multiple modes of stretch transduction were evaluated, including DC resistance changes due to strain at trace inflection points and high-frequency changes in self-impedance and inter-trace capacitance. DC resistance was found to increase linearly with stretch distance with sensitivities between 0.04 and 0.1 Ω/mm which are comparable to previously reported polyimide sensors but with a wider dynamic measurement range. Capacitance was also found to increase linearly with stretch distance after 2 mm, and high-frequency impedance increased nonlinearly, with different trace routing designs resulting in different patterns of impedance change with stretch.