III-Nitride Optoelectronic Chip Incorporating Double-Sided Structured PDMS Film for Shear Force Sensing

A compact biaxial shear force sensor based on a highly integrated III-nitride chip and a double-sided PDMS film is presented. The III-nitride chip has a cross-shaped configuration with a central light emitter and four surrounding detectors made from GaN epitaxial layers on a sapphire substrate. The PDMS film, with a fingerprint pattern at the top and a hemispherical structure at the bottom, undergoes deformation in response to external forces, thereby converting the force into optical changes to the chip and altering the photocurrent generated by the PD. The sensor with a size of 1 cm × 1 cm × 0.2 cm can detect shear forces ranging from -0.6 N to 0.6 N along both the X- and Y-axes. The laser-cut, cross-shaped design of the chip significantly enhances the sensitivity of the sensor, achieving an approximate fourfold increase, with sensitivities of 3.28 µA/N and 2.96 µA/N along the X- and Y-axes, respectively. The developed sensor is notable for its compactness, high sensitivity, cost-effectiveness, and ease of fabrication, rendering it well-suited for tactile applications that necessitate multidirectional force detection.