The research team from Hunan University proposed an easy and industrially applicable method to fabricate an extreme wettability surface on an Al-based superhydrophobic surface by a composite process of electrochemical mask etching and micro-milling, and achieved controlled evaporation, directional rebound and transport. of droplets on this surface over a wide temperature range for the first time.
The transport platform based on wettability differences will open up more applications in biochemistry, microfluidic systems, cell culture, and energy harvesting and utilization. This research was published in the Journal International Journal of Extreme Manufacturing.
The evaporation rate of droplets on superhydrophobic surfaces was lower than that of droplets on hydrophilic surfaces. Controlled evaporation of droplets on a hydrophilic micropit dot matrix, circular groove pattern, or other wettability difference patterns can be achieved by controlling the geometry of the hydrophilic pattern.
The directional bounce of droplets at different distances can be achieved by controlling the magnitude of the difference in substrate wettability over a wide temperature range. Droplets will rebound to the most wettable hydrophilic region, greatest degree of wettability difference, greatest rebound speed and distance.
When the substrate temperature is below the Leidenfrost boiling point, the droplet bounces back to the hydrophilic region. Rather, the droplets bounce vertically at the junction or move towards the superhydrophobic region due to the buoyancy generated by the vapor layer.
Controlled transport of droplets over a wide temperature range with confluence and split flow using Laplace pressure gradients on highly wettable surfaces has been achieved. Temperature gradient entrainment can be used to achieve directional and gravity-resistant transport of deionized water, anhydrous ethanol and kerosene with different viscosities, and the droplet migration rate increases with the temperature gradient.
By analyzing the phenomenon of droplet movement on wettable surfaces, researchers were able to understand the effect of wettability difference surfaces on droplet movement. The researchers found that the size of the hydrophilic zone at room temperature affected the rate of evaporation and the direction of transport of the droplets, which tended to bounce more towards the hydrophilic regions. However, the droplet bounces back to the superhydrophobic region at high temperatures.
The team investigated a promising method to industrially prepare surfaces differentiated by wettability, but the experimental technique they developed can be used for many different applications.
Yao Lu from Queen Mary University of London says “this is a very valuable and promising achievement and it’s just the beginning – we are already looking to use this technique to support the development of functional bionic surface structures. , which are needed in industries such as biochemistry, microfluidic systems, and energy harvesting and utilization.
Even the droplets sometimes take the stairs
Chengsong Shu et al, Fabrication of an Extreme Wettability Surface for Controllable Droplet Handling Over a Wide Temperature Range, International Journal of Extreme Manufacturing (2022). DOI: 10.1088/2631-7990/ac94bb
Provided by International Journal of Extreme Manufacturing
Quote: Controlled bouncing, evaporation and transport of droplets on a liquid-repellent surface (2022, October 24) retrieved October 24, 2022 from https://phys.org/news/2022-10-evaporation-droplets-liquid-repellent-surface . html
This document is subject to copyright. Except for fair use for purposes of private study or research, no part may be reproduced without written permission. The content is provided for information only.
#Controlled #rebound #evaporation #transport #droplets #waterrepellent #surface