Both pitcher plants and rice leaves inspired the design of a slippery rough surface (SRS) that outperforms state-of-the-art liquid-repellent surfaces in water harvesting applications.

Many water-harvesting technologies suffer from inefficiencies when water is attracted to a hydrophilic surface, forms a sheet and clings to the surface, making it hard to remove. Researchers from Pennsylvania State University and University of Texas at Dallas sought to combine different biological strategies to create a slippery solution for water harvesting.

Combining the slippery interface of pitcher plant with the surface architecture of rice leaf, which has micro/nanoscale directional grooves on its surface, allows water to be removed very easily in one direction but not the other. The rice leaf-inspired grooves whisk the water droplets away through capillary action or gravity, and the large surface area of the new SRS enables increased rates of water and fog harvesting.

Experiments confirmed that that these surfaces can collect tiny water droplets from air at a rate faster than many state-of-the-art surfaces. If produced at scale, the SRS can collect over 120 liters of water per square meter of the surface per day, and the water harvesting rate can be boosted by optimizing the SRS.

The researchers are now working on optimizing and scaling up the SRS with the goal to create highly efficient water harvesting systems for providing clean water in water scarcity regions.

The study is published in Science Advances.

The left panel depicts the new directional SRS, the middle panel is a slippery liquid-infused porous surface and the right panel is a superhydrophobic surface. The image shows a comparison of water harvesting performance of SRS vs other state-of-the-art liquid repellent surfaces. Source: Xianming Dai/Nan Sun/Jing Wang/Tak-Sing Wong, Penn State