Ion-Selective GaN Optopairs with Rapid Response and High Stability for Intelligent Biomimetic Sensing

Abstract Ion concentration variation can indicate dynamic physiological metabolism and environmental media changes. Although electrochemical biosensors with high sensitivity and selectivity are widely used, achieving rapid response and minimal signal drift remains challenging. Herein, a gallium nitride (GaN) chip was functionalized with an ion-selective membrane to enable highly sensitive, fast, and stable optical readout. During real-time continuous monitoring, a minimized response time of 0.15 s with high signal recovery was achieved, and the drift was reduced to about 0.5 μA/h and 0.3 μA/h for Na+ and K+, respectively. To reduce the cross-interference in mixed ion analysis, a dual-channel ion decoding algorithm was implemented to improve the accuracy. The sensor was integrated into a flexible platform for real-time sweat electrolytes monitoring during exercise and further applied to a robotic fish for biomimetic detection of abnormal ion-concentration hazard zones and closed-loop obstacle avoidance, demonstrating its potential for wearable health monitoring and environmental perception.