Bioinspired Strategies for Directional Water Transport in Asymmetric Membranes

The directional transfer of water is an important process for many living organisms and an increasingly important technological concept that enables applications such as fog harvesting, separation processes, smart packaging, and advanced textiles. Among the various strategies for achieving directional permeation, asymmetric dense polymer membranes have proven particularly effective. Over the past decade, research on natural and engineered systems has expanded significantly, leading to numerous innovative material solutions. After providing a historical perspective on research on directional biological membranes, this review summarizes the fundamentals governing asymmetric permeation in dense polymer membranes, highlights recent advances concerning the design, fabrication, and characterization of such structures, and discusses possible applications. Finally, current challenges and future opportunities for advancing this field toward scalable and multifunctional systems are presented.