Smart Control of Wetting
Inspiration from the natural world has allowed us to design surfaces that control water on them by either being superhydrophobic or highly water-shedding. However, we also have tools available to us that are not available to the natural world. For example, we can use a voltage to alter the shape of a droplet resting on a surface to create a variable focal-length liquid lens, and we can apply an electric field to alter how much a dielectric liquid wets a surface or to induce a film of the liquid.
Some of the research in these areas involving the groups at Nottingham Trent University and the University of Edinburgh is described below.
Superspreading without
surfactants
![](https://naturesraincoats.com/wp/wp-content/uploads/2021/03/Superspreading.png)
Droplets can be forced to spread further and faster than would normally occur by using a localised electric field at the solid-liquid interface.
Dewetting of a liquid film
![](https://naturesraincoats.com/wp/wp-content/uploads/2021/03/dewetting-droplet-large-600x338-5.jpg)
An electric field can be used to create a liquid film on a phobic surface. Switching off the electric field allows the recoil of the film (“dewetting”) into a droplet to be observed.
Voltage programmable optics
![](https://naturesraincoats.com/wp/wp-content/uploads/2021/03/Liquid-Optics-rescaled-4.jpg)
A static wrinkle can be programmed onto a liquid film using an electric field. This can be used to steer optical beams and separate the colours in white light.
Bubble control
![](https://naturesraincoats.com/wp/wp-content/uploads/2021/03/Bubble_control-2.jpg)
Using an electric field, a bubble of air can be detached from an inverted surface and its position below the surface controlled.
Shaping liquid films
![](https://naturesraincoats.com/wp/wp-content/uploads/2021/03/Shaped_film-rotated.jpg)
By designing electrode overlaps, the electric field can be shaped into geometric patterns. This allows circular, rectangular and other shapes of films to be created.
Controlling instabilities
![](https://naturesraincoats.com/wp/wp-content/uploads/2021/03/Instabilities.jpg)
Thin liquid stripes on solid surfaces can naturally break up into patterns of droplets. The modes of break-up can be controlled using electric fields.