Gravity-Driven Air-Liquid Interface Flexible Sensor for Human Motion Detection

Abstract

This study introduces a novel gravity-driven air-liquid interface flexible sensor (GALIFS) for detecting human motions. GALIFS leverages gravity-induced liquid flow to generate angle-dependent electrical signals, eliminating the need for material deformation (e.g., stretching or compression) during operation. Unlike conventional inertial sensors (limited by rigid designs causing discomfort) or existing flexible sensors (reliant on stress-induced signals and high material durability), GALIFS overcomes these constraints through its unique gravity-driven mechanism. Furthermore, GALIFS operates without requiring perfect skin adhesion, significantly enhancing user comfort. GALIFS achieves a wide angular detection range (0°–180°) with high stability (over 16000 cycles). Additionally, it can identify a diverse range of human motions, including neck bending, spine bending, squatting, jumping, walking, and running. A real-time lying posture monitoring system for bedridden patients is further developed, showcasing its medical potential. Following successful mitigation of liquid evaporation issues, GALIFS may have significant potential for applications in various scenarios, including medical rehabilitation and sports training.