Gas-liquid two-phase bubble flow spinning for hydrovoltaic flexible electronics.

Hydrovoltaic technologies that generate electricity by absorbing or transferring free water without chemical reactions have been explored as potential candidates for renewable energy. Self-powered flexible sensors, including hydrovoltaic fibers, are becoming an important research direction in the field of renewable energy. However, integrating sensing and power generation in functional fibers remains challenging due to the need to regulate water movement to achieve performance differences. Here, we present a gas-liquid two-phase flow spinning method, inspired by spider multimodal spinning, that uses bubble-triggered spinning-liquid deformation to fabricate hollow, solid spindle, and ratchet tooth-shaped fibers. These structures alter water adsorption and transfer behaviors, making them suitable for targeted applications in hydrovoltaic devices for energy and sensing fields. Shaped fibers prepared from alginate-bridged MoS₂ enable a wide range of hydrovoltaic applications. The obtained fiber has a power density of 2.18 mW/cm, stable operation at 2.1 V for 43 hours, and sensitivity of 9.36 mV/RH%/s, leading to the development of smart masks for nasal cycle monitoring, diagnosis, and therapy as potential applications. Spinning materials were extended to materials such as carboxymethyl cellulose, polyvinyl alcohol, etc., inspiring the design of structure-responsive hydroelectric materials and advancing textile electronics.