Several years ago, researchers at the U.S. Department of Energy’s Brookhaven National Laboratory introduced a nanoscale surface-texturing way for imparting complete water repellence to substances, a property inspired by insect exoskeletons that have small hairs designed to repel water by trapping air. Their way leverages the ability of substances known as block copolymers to self –assemble into structured patterns with dimensions measuring only tens of nanometres in size.
The researchers employed these self-organized patterns to prepare nanoscale textures in a range of inorganic substances, comprising glass, silicon, and some plastics. Initially, they studied how altering the shape of the textures from cylindrical to conical impacted substances ability to repel water. Cone-shaped nanotexturesproved much better at forcing water droplets to roll off, carrying dirt particles away and leaving surfaces completely dry.
Now, working with team in France – from ESPCI Paris Tech, EcolePolytechnique, and the Thales Group, they have further shown that the optimized nanotextures have excellent anti-fogging potentials. Head by David Quere of ESPCI and EcolePolytechnique, the research offers a fundamental comprehending that may inform novel designs car condensing coils of steam turbine power generators, car and aircraft windshields, and other substances prone to fogging.
“Numerous textured substances can repel water, with millimetre-size water drops bouncing off their surfaces, but numerous of these surfaces fail when exposed to humid or foggy conditions,” says Charles Black, director of Brookhaven Lab’s Centre for Functional Nanomaterials, the DOE Office of Science User Facility where Black and former researcher Antonio Checco of Brookhaven’s Condensed Matter Physics and Materials Science Department and former CFN postdoctoral research associate AtikurRahman structured the nanotextures.
Fog occurs when warm, moist air hits a cooler surface and creates water droplets, a procedure known as condensation. When water droplets are similar in size to the structural features of a textured hydrophobic surface, they can get inside and grow within the texture, instead of remaining on top. Once the texture fills up, water landing on the substance gets stuck, resulting in the appearance of fog.
Researchers have primarily identified that the wings of cicadas, which are covered by nanosized cone-shaped textures, have the potential to repel fog by resulting in water droplets to spontaneously jump off their surface – a procedure caused by the effective conversion of surface energy to kinetic energy when two droplets combine.
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