Enhancing ‘breath figures’ using electric fields efficient condensation

More fundamental insights into the theoretical analysis of dropwise condensation at a wide range of energy levels.

Enhancing 'breath figures' using electric fields efficient condensation
Image: University of Twente

In physics, the term breath figures are used to describe dropwise condensation patterns. The evolution of this patterns is only possible by applying a thin water-repellent coating that improves droplet mobility. But now scientists at the University of Twente suggests that it is also possible to actively influence the condensate droplets by embedding electrodes in the surface.

A new finding suggests that the evolution of these patterns and roll-off of droplets can be changed strongly under electric field effects ‘electrowetting’ – leading to higher heat transfer rates. Applying electric fields changes the ‘wetting state’ of the surface, known as electrowetting.

Under electrowetting, the evolution of condensation can be controlled. It’s all because of the electric field influences the distribution and the size of the droplets. They merge faster caused by the electric forces and form bigger droplets in a shorter time. Furthermore, they move to become aligned with each other.

Development of droplet size and distribution in time, without electrowetting (upper images) and with electrowetting (lower images)
Development of droplet size and distribution in time, without electrowetting (upper images) and with electrowetting (lower images)

As they merge together, their net surface coverage is reduced compared to typical cases, leaving more ‘bare surface’ for further condensation.

Therefore, the breath figure undergoes a major transformation of properties like surface coverage, size distribution and average radius. Furthermore, the droplets roll off faster on the surface. This increased mobility leads to more efficient heat transfer.

The research has been done in the Physics of Complex Fluids group of Prof Frieder Mugele, part of the MESA+ Institute for Nanotechnology of the University of Twente. It was supported by the Netherlands Organisation for Scientific Research (division Applied and Engineering Sciences) and the Vici-programme.

The study is published in the Physical Review Letters.