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

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 microgrooved 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.