Deformation-Modulated Hydrovoltaic Effect for Continuous Self-Powered Strain Sensing

Abstract

Strain sensors capable of continuous, self-powered operation are critical for biomedical and environmental monitoring systems, yet remain challenging to realize. Here, we report a hydrovoltaic self-powered strain sensor (HVSP) based on flexible silicon nanowire arrays. The sensor exploits deformation-induced modulation of hydrovoltaic electrical output, enabling persistent monitoring of both dynamic and quasi-static strains without external power sources, which effectively overcomes the transient-signal limitation of existing self-powered strain sensors. The HVSP sensor exhibits a high gauge factor of −135, comparable to commercial silicon strain gauges, alongside excellent cyclic stability and durability. Integration with contact lenses demonstrates sensitive intraocular pressure monitoring across physiological ranges (7.5–30 mmHg) with a responsivity of −4.4 mV/mmHg and detection resolution of 0.74 mmHg, performance that surpasses clinical tonometry standards. Biocompatibility tests confirm cytocompatibility and conformal ocular surface integration, while powering an LED in simulated tear reveals the potential of the HVSP sensor for seamless integration into functional systems and straightforward visual feedback. This work introduces a novel hydrovoltaic sensing mechanism that not only enables high-performance physiological monitoring but also provides a broadly applicable strategy for self-powered strain sensing in diverse scenarios, paving the way for highly integrated autonomous sensing systems.