Natural alginate fiber-based actuator driven by water or moisture for energy harvesting and smart controller applications

Many idle green resources exist in nature, including water and moisture, which are ubiquitous but have no great value. In this work, we, for the first time, innovatively twisted a gel-state natural alginate fiber prepared by wet spinning to obtain a fiber-based actuator that shows remarkable performance under water and moisture stimulation. Owing to the excellent swelling and contraction properties in response to water, the twisted alginate fiber-based actuator underwent a rapid reversible rotational motion with a rotation speed of 13 000 rpm and a revolution of over 400 turns. Moreover, the shape, as well as the performance, of the twisted fiber remained stable, even after 400 cycles. The excellent driving performance, simple preparation, low-cost production, and the industrialization development trend render the natural alginate fiber-based actuator a new type of green-energy material as a viable replacement for the existing torsional fiber-based actuators made of GO and nanotube materials. In addition, we designed the twisted fiber into a hydro-generator, a smart rainy curtain, breathable fabric, and a smart crane, which have great application prospects in future intelligent systems.