Dual-function GaN QWD chip for real-time joint flexion and gesture recognition

GaN-based quantum well diodes (QWDs) exhibit the physical phenomenon of simultaneous emission and detection, offering a promising pathway toward compact, multifunctional optoelectronic platforms. We present a wearable joint flexion sensing system based on a dual-QWD chip operating at ∼460 nm. One QWD serves as a stable light emitter, while the other detects local optical field changes induced by joint bending. The chip is integrated onto a flexible printed circuit board and worn on the outer side of joints such as the elbow, wrist, and fingers, providing good skin compatibility and thermal safety. Optical signal variations are processed using a multilayer perceptron model to classify six hand gestures, including finger-count patterns and a clenched fist. A fivefold cross-validation confirms gesture recognition accuracies exceeding 97% across all categories. This work demonstrates a compact and reliable real-time gesture sensing method, underscoring the potential of GaN-based QWDs in next-generation wearable interactive systems.