Dropwise condensation plays an important role in nature and industrial applications, such as water harvesting, air conditioning, desalination, anti-fog and thermal management. The evolution of surperhydrophobic surfaces promotes dropwise condensation in easily removing condensing droplets to enhance mass and heat transfer. Droplet departure size is at small-scale through droplet jumping by releasing surface energy but the existence of vapor flow and gravity can lead to droplets return. Droplet sweeping by gravity can expose large re-nucleation area for next condensation, which takes a long growth and shedding cycle due to the droplets have to exceed the capillary length to take advantage of gravity. Here, we demonstrate that condensation micro-droplets could sweep on the horizontally placed surface spontaneously by implanted a gradient electric field into an electret with superhydrophobic surface. This sweeping movement can take place at much smaller size and earlier departure time compared to gravity shedding, which is attributed to the fact that coalescence-induced charging of condensing droplets at a very small length scale. Condensing droplets undergo coalescence-charging, snowball-like moving and self-propelling, the process repeats itself in a periodic manner. Utilizing a gradient electric field to propel the charged droplets to sweep other condensation droplets shift drop size distribution timely and lower surface coverage. This controlled sweeping behavior opens up a novel avenue for condensation enhancement.

Snowball-like sweeping removal of dropwise condensation propelled by charge density gradient

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.