Flexible and sensitive three-dimension structured indium tin oxide/zinc aluminum oxide/Cu composites thin-films pressure sensors for healthcare monitoring

•Sensitive, simple and wearable ITO/AZO/Cu piezoelectric film sensors are proposed.•The flexible sensors present stable output voltage during 1000 loading cycles.•Doping concentration in AZO play a key role in piezoelectric performance.•ITO/AZO/Cu films prepared on microstructures show significantly higher sensitivity. Flexible pressure sensors play a crucial role in large-scale commercial applications, such as health monitoring, robotics, and smart devices. However, mass production of piezoelectric sensors for industrial applications is limited by their complex and cost-intensive fabrication processes. In this study, sensitive, simple, and wearable piezoelectric sensors were prepared by magnetron sputtering of indium tin oxide/zinc aluminum oxide (AZO)/Cu composite thin films onto three-dimension structured polydimethylsiloxane) substrate. The prepared flexible sensors delivered output voltages of −200 mV and +200 mV during 1000 loading and unloading cycles, respectively, showing an outstanding sensitivity and cycling performance. The piezoelectric performance of AZO films is primarily determined by the doping concentration of aluminum in AZO; the output voltage of the sensor with the optimal doping concentration was approximately 340 % higher than that of the undoped sample. Finite-element simulations demonstrated that the substrate with a square platform exhibited the most uniform stress distributions as well as the highest stress on its microstructure surface, which resulted in a high stress and sensitivity of the thin-film sensors. Experiments revealed that the incorporation of a microstructure enhanced the output voltages of the sensors. In particular, the output voltage delivered by the flexible sensors with square microstructures was approximately 60 % higher than that exhibited by those without microstructures. [Display omitted]