Gastrointestinal-Peristalsis-Inspired Hydrogel Actuators for NIR-Controlled Transport of Viscous Liquids

Liquid transportation is fundamentally important in microfluidics, water collection, biosensing, and printing, and has attracted enormous research interest in the past decades. However, despite substantial progress, it remains a big challenge to achieve the controlled transport of viscous liquids (>100 mPa s) commonly existing in daily life and the chemical industry. Inspired by the gastrointestinal peristalsis of mammalians that can efficiently transport viscous chyme (viscosity up to 2000 mPa s) by the synergistic combination of contraction driving force and lubrication, here, the design and construction of double-layered tubular hydrogel actuators for directional transport of highly viscous liquids ranging from ≈1000 mPa s to >80 000 mPa s under the control of an applied 808 nm laser, which is attributed to the cooperation of outer layer contraction and water film lubrication of the inner layer, is reported. It is demonstrated that the actuators are capable of transporting polymerizing liquid whose viscosity significantly increases to ≈11 182 mPa s in 2 h. This work paves a new avenue toward directional transport of highly viscous liquids, which not only expands the research scope of liquid transportation, but will spur the design of new liquid actuators with potential applications in viscous-liquid-based microfluidics, artificial blood vessels, and soft robots.