Matchbox Janus membrane fog collector with highly efficient directional transport†

Coordinating the droplet capture, transport, and shedding processes during fog collection to achieve efficient fog collection is a major challenge. In this study, a copper mesh with different wettability was prepared by chemical etching and thiol modification. The Cu(OH)₂ needle structure on the surface of the samples was characterized by FE-SEM and EDS tests, and the surface of the samples was chemically analyzed by infrared and XPS analyses. A Janus membrane matchbox fog collector was thus designed and assembled with directional transport properties. While achieving directional transport of fog droplets on a grid, the fog capture efficiency was also improved. We built a fog collection test rig in the laboratory and tested the samples at a fog flow rate of 0.8 m s⁻¹, and the highest fog collection efficiency reached 6.9 g h⁻¹ cm⁻², enabling a long-term and efficient fog collection process even in dynamically changing fog environments. This study demonstrates a wide range of applications to achieve green, low-cost, and efficient fog collection strategies.