Multi-directional millinewton force sensing for human-computer interaction based on an optoelectronic-integrated flexible tactile device

Flexible optical force sensors have shown great potential in human-computer interaction (HCI), health monitoring, and wearable devices. However, conventional optical force-sensing systems typically require separate light sources and photodetectors, leading to bulky system architectures and low integration. This work presents a multi-directional millinewton sensor based on a GaN monolithically integrated optoelectronic chip and a flexible optoelectronic tactile device (FOTD). The chip integrates one micro-scale multi-quantum-well (MQW) transmitter and four-quadrant MQW receivers on the same substrate, enabling compact on-chip integration of light emission and detection. The FOTD uses a polydimethylsiloxane (PDMS) structure as an elastic substrate, with an embedded optical fiber for light routing and force transmission. The device exhibits a system-level sensitivity of 4.5 μA/N over 0-250 mN, a response time of 80 ms, and a force resolution of 3 mN. It can achieve multi-directional force tactile sensing-including normal force (Z), tangential force (X-Y), and oblique forces (45°). Furthermore, real-time four-directional control in a Snake game is demonstrated as a proof of concept. With its integrated design and excellent repeatability, this sensor provides a promising solution for wearable electronics, gesture recognition, and interactive control.