Plastic foil micro-grooved by embossing enhances dew collection without aging effects

Abstract

Low-tech, radiative, and recyclable plastic foil is considered for the passive collection of dew water. Fashioning micro-grooves at their surface by hot embossing improves by a large factor the collection of even tiny water drops. We show that this improvement is conserved under harsh outdoor conditions. The ability of the micro-grooved foil to collect condensed water is measured by the latency time (tl) to collect the first drop at the bottom of a vertical substrate. Compared to the same smooth foil, tl is smaller for the micro-grooved foil by an order of magnitude. Under severe outdoor conditions (dust storm, heat waves) the properties of the micro-grooved foil are preserved after 6 months, whereas the collection properties of the smooth foil have decreased by 50%. The basic reason is the insensitivity of the water collection mode to the evolution of surface wetting and roughness properties. Such a low-cost, scalable, and robust material should find applications in passive water harvesting devices to supply supplementary fresh water in regions where water is, or is becoming, a scarce resource.