A new surface design that induces the condensation of water vapour, and the subsequent shedding of the resulting water droplets up to ten times faster than state-of-the-art surfaces can achieve, is described online in Nature this week.
In many applications such as water-harvesting systems and thermal power generation, surfaces need to be designed to allow water droplets to grow rapidly via condensation, but also to be shed as quickly as possible. Current approaches are limited in that they can promote either droplet growth or shedding, but rarely both. Joanna Aizenberg and colleagues brought together three structural components found in nature to design a new surface. They combined the water-condensation-promoting capabilities of bumps on the backs of Namib desert beetles with the ability of asymmetric cactus spines to collect and transport water. The coupling of droplet growth and fast directional transport was further enhanced by including a slippery surface coating inspired by pitcher plants.
The authors conclude that the surface, which promotes growth and transport of water droplets both against gravity and against an unfavourable temperature gradient, holds promise for applications including water harvesting and heat exchange.