Bio-inspired soft Janus membrane with double asymmetric characteristics for self-driven fog collection and transport

The scarcity of water resources has intensified interest in fog collection technologies. Drawing inspiration from natural organisms, Janus-structured materials have garnered considerable attention due to their high-efficiency fog water collection capabilities. However, the current Janus materials used for fog collection typically possess only single wettability, resulting in suboptimal efficiency. Spontaneous multidimensional unidirectional fluid transport in porous materials is achievable with specific structural designs and environmental conditions. Herein, we present a soft Janus membrane fabricated using a simple mechanical drilling technique combined with asymmetric surface modification. Its conical micropores combine both geometric and internal wettability gradients, creating a dual‐gradient architecture. Synergistic surface‐energy differentials and Laplace pressure within the conical pores drive spontaneous, unidirectional droplet penetration and storage. Compared to traditional Janus materials with a single asymmetric structure, the dual-gradient structure significantly enhances fog collection performance and water storage capacity. This innovative automatic fog collecting membrane offers a promising avenue for efficient fog collection systems to address the freshwater crisis. Furthermore, it provides a fresh perspective for the exploration and advancement of oil–water separation technologies and other purification methods.