Structural robustness and actuation performance of multilayered thin-film actuators based on Ni-Co flexible substrate

Abstract

This paper presents a comprehensive evaluation of multilayered thin-film actuators based on metal substrates made of Ni and Co alloys. The focus was on improving the structural robustness through appropriate adhesive layers and evaluating their fundamental performance and long-term stability. We conducted nanoscratch testing and scanning electron microscopy to identify the optimal adhesive layers that significantly enhanced the adhesive strength. Following the evaluation, no instances of cracking or peeling were observed in the multilayer thin film where a Ti layer serves as an adhesion mediator between the Ni and Co thin film and the SiO2 and Si3N4 insulating layers. This indicates that this specific layer configuration provides superior structural robustness compared to multilayer thin films with alternative compositions. In addition to enhancing the structural robustness, we comprehensively evaluated the fundamental performance and long-term cyclic stability of the multilayered thin-film actuators. The actuators demonstrated exceptional characteristics including low power consumption, substantial displacements (1.58 mm at 120 mW, corresponding to an input voltage of 5 V), rapid response times, and high operating speeds. The endurance of the actuator was verified through long-term cyclic testing by subjecting it to a sinusoidal excitation for an extensive duration of 1.15 million cycles. This test demonstrated the stability of the actuator in maintaining its functionality and reliability even under prolonged operating conditions. Thereby, the test verified its structural robustness and potential for practical applications.