Liquid Shuttle Mediated by Microwick for Open‐Air Microfluidics

Abstract Microfluidics has experienced rapid progress in additive manufacturing and microfluidic soft robots. The design of microfluidics is already moving into a more intelligent, integrated, and detachable direction. However, the pipeline resistance needs more external energy input to achieve high flow speed. Guided transport of liquid in the open‐air‐space microfluidics will be an effective solution. Inspired by the water shuttle on the pitcher plant tendril, herein, an open‐air microfluidic transport device is designed that consists of a superhydrophilic microwick with multi‐microgrooves by stereolithography. The liquid film confined in microgrooves can promote rapid fluid shuttle on the wet surface to enhance transport rate and inhibit the Rayleigh‐Plateau instability from forming larger dripping drops. The dripping volume and threshold Capillary number are optimized for effective liquid transport and drainage. State‐of‐the‐art microwick liquid shuttle technologies can guide liquid continuously in a prescribed direction or into multiple directions with 98% transport efficiency (the ratio of liquid collection volume and liquid injection volume) for water and 97% for ethanol in the closed‐open‐closed space. The proposed mechanism has the potential to streamline microfluidic applications—and, therefore, accelerate relevant liquid delivery development and ultimately their applications in microfluidic chip and additive manufacturing.