High-speed magnetic control of water transport in superhydrophobic tubular actuators

Directed transport of a small amount of water is a basic issue and has attracted extensive attention due to its importance in a wide range of applications, such as water collection, microfluidics, printing, bioanalysis, and microchemical reactions. Various strategies based on constructing a surface tension gradient or Laplace pressure gradient have been developed to realize directional water transport. Typically, electrostatic forces and magnetic fields are utilized to achieve high-speed water transport on open superhydrophobic surfaces. However, these methods suffer from water evaporation or contamination. Here, we report a magnetic superhydrophobic tubular PDMS actuator for directional water transport. The actuator deformed under an applied external magnetic field and actuated the water droplet to transport along the moving direction of the magnet. The water transport velocity reached 16.1 cm/s. In addition, as the inner surface of the actuator is superhydrophobic, the water droplet showed weak interactions with the surface and presented negligible mass loss during the transport process. The results of this work may inspire new design of actuators for directional water transport with high speeds.