Flexible topological liquid diode catheter

Spontaneous and directional transport of various liquids in open and closed spaces is of great importance in various energy, water, and medical applications. Despite extensive progress in engineering diverse open surfaces to rectify liquid transport, the implementation of the diode-like liquid transport in a closed system is still rare. In this study, we present the design of flexible liquid diode catheters internally decorated with asymmetric reentrant structure that allows for the efficient and unidirectional transport of diverse liquids. We also elucidate that the hydrodynamic transport behaviors in the closed diode catheters are primarily dominated by the interplay between the surface effect and the bulk effect, which are distinctly different from those on open liquid diodes. The flexible liquid diode catheters can preserve their directional transport behaviors even under mechanical bending or twisting and under various liquids from low-surface-tension liquids, medical solutions to lubricant oils. The combination of extraordinary flexibility, durability, and stability promises the development of liquid transport devices that can work in various configurations and applications.