Phys.org September 16, 2021
A liquid deposited on a surface tends to move along directions that reduce surface energy, which is mainly dictated by surface properties rather than liquid properties, such as surface tension. Achieving well-controlled directional steering remains challenging because the liquid-solid interaction mainly occurs in the 2D domain. An international team of researchers (China, Hong Kong) has shown that the spreading direction of liquids with different surface tensions can be tailored by designing 3D capillary ratchets that create an asymmetric and 3D spreading profile both in and out of the surface plane. Such directional steering is also accompanied by self-propulsion and high flow velocity, all of which are preferred in liquid transport. The work could open a new wave of using 3D surface structures for intelligent liquid manipulation for various scientific and industrial applications, such as fluidics design and heat transfer enhancement…read more. TECHNICAL ARTICLE
Ethanol (left) and water (right) flow in different directions on the Araucaria leaf-inspired surface. Credit: City University of Hong Kong