True “Liquid Diode”: Check Valve@Janus Membrane to Achieve an Extremely High Reverse Breakthrough Pressure

Janus membranes, widely recognized for their remarkable unidirectional permeability, can achieve spontaneous liquid transport from the hydrophobic sides to the hydrophilic sides while impeding liquid flow in the opposite direction. However, the current Janus membrane only possesses limited reverse breakthrough pressure (RBP) (<20 cm water height), which is a key factor in determining the unidirectional liquid transport function. Here, inspired by the one-way blood transport function of heart valves, a solution to the issue above is proposed in the form of a Janus membrane integrated with a gravity-assisted check valve (check valve@Janus membrane). As a result, the breakthrough pressure of the check valve@Janus membrane was observed to be nearly zero in the positive direction. More importantly, the RBP had been observed to reach up to 4 m. This considerable advance in RBP is predominantly attributable to the unparalleled resistance of the check valve to the backward flow. The check valve@Janus membrane results in a perfect unidirectional flow, thereby achieving the concept of a true "liquid diode". This innovation offers a novel method for enhancing the RBP of a Janus membrane, opening up a wealth of potential avenues for future applications in clinical medicine, microfluidics, and other disciplines.