Impact Force Sensors Based on GaN Optical Devices With Micropatterned PDMS Sponges

In this work, the fabrication and characterization of impact force sensors based on GaN optical devices with microstructured polydimethylsiloxane (PDMS) sponge are presented. Fabricated through a low-cost and scalable pattern transfer process, the PDMS sponge with porous structure and surface micropatterns can effectively convert the impact force into contact change at the boundary of the GaN device, thus modulating the amount of light reflected in the on-chip detector. In addition to examining the luminescence and photodetection capabilities of the GaN devices, the effects of PDMS porous structures on the impact force are investigated. By incorporating the optimized PDMS sponge with surface micropatterns, the sensor exhibits high sensitivities of 0.67 and 0.21 %/N for the impact force ranges of 2.5–39.9 N and 39.9–67.2 N, respectively. Through dynamic experimental measurements, the sensor also shows the fast response time (6.07 ms) and recovery times (7.30 ms), and the high stability of the sensor over 12 000 cycles. The potential uses of the sensor for impact force detection in wearable applications are demonstrated. The developed sensor has significant advantages such as high compactness, quick response, and ease of use, making it well-suited for the practical measurement of impact stimuli.