Kirigami Strain Sensors Microfabricated From Thin-Film Parylene C

A kirigami-based strategy was investigated for strain transduction, using serpentine gold traces embedded in thin-film Parylene C. Multiple kirigami slit designs were evaluated via COMSOL simulation and mechanical force testing; sensors having tightly packed slits stretched up to 17.5 mm (350% strain) before mechanical failure and 9 mm (180% strain) before electrical failure. Strain transduction was achieved by monitoring DC resistance changes during stretching. DC resistance linearly increased with strain, with sensitivities up to 0.16 Q/mm (gauge factor = 0.007) and minimal hysteresis. High-frequency trace impedance and inter-trace capacitance were also investigated during strain cycling. Capacitance increased with strain and high-frequency impedance show a nonlinear strain relationship. The biocompatible construction and extremely low profiles (20 μm thick) of these sensors are attractive for minimally invasive in vivo strain sensing applications.