With water scarcity slowly becoming widespread in both rural and suburban neighborhoods, water harvesting machines are expected to increase in demand in the coming years. This is why a team of researchers from Penn State and the University of Texas at Dallas recently designed a new slippery surface for water harvesting applications. This slippery solution, the slippery rough surface (SRS), was achieved through the process of biomimicry.
SRS aims to increase the efficiency of the harvesting process through inexpensive biological strategies. Simon Dai, assistant professor at the University of Texas at Dallas, took inspiration from the pitcher plant, which is carnivorous. When insects land on the walls of these plants, they slip into the digestive system because the walls have a slippery surface.
Inspiration for the SRS’ design also came from the surface architecture of a rice leaf. According to Dai, it “has nanoscale directional grooves on its surface that allows water to be removed very easily in one direction but not the other.” He designed the SRS with additional directional grooves to give the surface a microscale roughness. This increased the surface area, allowing the surface to attract more water.
Experiments show that the SRS can collect water droplets from the air at a faster rate compared to other state-of-the-art surfaces. Simulations of the SRS material in actual water-harvesting applications show it could collect an estimated 120 liters of water per square meter of the surface per day if produced at scale.
Water harvesting requires highly efficient procedures and equipment. Current technology used has been suffering at a loss in total water harvested due to inefficiencies in the surfaces used. The most commonly used are hydrophilic surfaces. These were once an important breakthrough because of their high surface energies, which are able to attract water. However, when water is attracted to a hydrophilic surface, it forms a sheet and sticks to the surface. This prevents water from flowing consistently, making the process inefficient.
If a surface traps a water droplet too tightly, it cannot move fast enough for capture at an efficient rate. This means some water may be lost due to evaporation before it can even be captured. This prolongs the process and results in less water harvested.
By studying how living organisms collect water, they were able to “create a surface that can both capture and direct water droplets efficiently.” According to the team, the goal was to develop the pitcher plant-inspired slippery surface with hydrophilic chemistry. By optimizing and scaling the SRS, it can improve water-harvesting systems, ultimately making the process more efficient.
Findings from tests by the research team were released online March 30. It can be found in the open-access journal, Science Advances.