Janus Membranes with On-Demand Control of Droplets Used in Blood Testing and Information Encryption

Janus membrane holds paramount significance across diverse domains, such as chemical reactions, microfluidics, multiphase separation, and purification. Herein, we propose a new Janus membrane for programmable control of three-phase contact lines (TPCLs) of droplets during the positive transportation process. Unlike the predictable positive transport mode on conventional Janus membranes (namely, TPCLs remain essentially unchanged), Janus membranes with engineering wettability dots (JM-EWDs) can control TPCLs of droplets to move along predetermined trajectories. This is attributed to the synergistic effect of longitudinal and transverse wettability gradients at the engineering wettability dot. More importantly, inspired by this unique structure, we propose a new and simple method for preparing Janus membranes. Finally, we demonstrate the applications of JM-EWDs in emerging fields such as blood type testing and information encryption. We believe that our work can further promote the development of Janus membranes and provide new insights for the programmable control of droplet TPCLs, enriching the theory of unidirectional liquid transport.