Dual-bioinspired fabrics with radiative cooling and heterogeneous wettability for passive atmospheric water harvesting

Passive atmospheric water harvesting (PAWH) is a viable strategy for decentralized freshwater production, particularly in high-humidity regions. However, current materials often lack the intrinsic thermal gradient required to trigger vapor condensation during fog-free periods, and suffer from solar-heating effects. In this work, we hypothesize that the integration of sub-ambient radiative cooling with dual-bioinspired heterogeneous wettability can effectively extend the operational window for water harvesting. Inspired by the self-cooling of white beetles and efficient water collection of Namib Desert beetles, we developed a dual-bioinspired fabric that integrates passive radiative cooling with heterogeneous wettability. The fabric achieves a low solar absorptivity of ∼1.8% and a high selective mid-infrared emissivity of ∼92.9%, maintaining an average sub-ambient temperature drop of ∼6.58 °C to sustain a persistent vapor pressure gradient for water condensation. The hydrophilic regions serve as optimized nucleation sites to lower the energy barrier, while the hydrophobic matrix facilitates rapid droplet growth and removal. Mechanistic analysis reveals that this integrated design effectively suppresses undesirable filmwise condensation by ensuring a continuous cycle of vapor nucleation, droplet growth, and droplet removal. The integrated design enables an efficient water collection rate (WCR) of 20.14 mg cm⁻² h⁻¹ in high-humidity environments and 2.26 g cm⁻² h⁻¹ under foggy conditions. This work demonstrates that synergizing radiative cooling with surface wettability control effectively enables continuous water production across varying moisture conditions, providing a robust solution for freshwater scarcity.