To initiate a process called “Dynamic Dewetting,” the researchers will use electrical voltages to force liquids placed on certain types of surface to form specific shapes, such as triangles and squares, and then retract.
The study aims to provide new understanding of how liquids can behave and interact and will have important implications for industrial use. Screen printing, for example, is only successful because of the way that the ink droplets interact with the solid surface. This enables them to form the final shapes that one wants them to appear in.
In 2016, Science Advances published findings from the same team after it had observed, for the first time, the dewetting process and how to control how liquids spread out on surfaces. The techniques discovered have been implemented into software for use throughout the printing industry.
Professor Glen McHale is the principal investigator on the study.
“When a liquid is deposited on a smooth surface, the wetting process means that it spreads across the surface until it becomes a film or reaches an equilibrium droplet shape,” McHale said. “If we think about liquids splashing, for example, the splash spreads out in a film as far as it can go across the surface. Look closely and you’ll see it becomes flatter in the middle and fatter around its edges. Dewetting is the opposite of this process and occurs when a fluid retracts from a surface and forms a droplet.
“In this study, we will look at liquid that normally wouldn’t form a film on a smooth surface,” he continued. “By introducing an electrical voltage, we will encourage the liquid to spread into a non-naturally occurring shape, such as a triangle, a square or a star. We also intend to investigate new ways in which we can detach and reattach droplets or bubbles onto surfaces in a controlled manner.
“This science has never previously been possible. Our analysis of how the liquids behave and evolve will provide the industry with the ability to finely control the application of liquid films for printing or coatings,” McHale concluded.
Northumbria’s Smart Materials and Surfaces Laboratory researches how surfaces with particular properties, or with properties that can be changed by external forces, can shape liquids. They also undertake research into how surfaces can reduce drag and be made either super-repellent or super-slippery.