Drop Self-Propulsion on Biphilic Liquid Surfaces
The ability to define an apparent contact angle on a lubricant-impregnated surface allows us to speak of patterning the wettability of such liquid surfaces. If we immobilize silicone oil next to Krytox oil then a droplet of water placed on the boundary of the two will spontaneously move to the silicone oil side because it has greater wettability. In the video below, the region to the left is silicone oil and the region to the right is Krytox oil. When a droplet of water is released onto the boundary between the two oils, it immediately and spontaneously moves to the silicone oil side.
We can use this idea to geometrically pattern surfaces of liquid-lubricants. The image below shows a wedge-shaped region of more wettable olive oil in a background of less wettable Krytox oil.
Water droplets self-propel away from the apex of the wedge, as seen in the video below.
We can create stable patterns of liquid surfaces with sizes of less than the width of a hair (i.e. 50 microns).
Read more about the process in the papers below.
Publications
- Droplet Self-Propulsion on Slippery Liquid-Infused Surfaces with Dual-Lubricant Wedge-Shaped Wettability Patterns M. Pelizzari, G. McHale, S. Armstrong, H. Zhao, R. Ledesma-Aguilar, G.G. Wells and H. Kusumaatmaja, Langmuir 39 (2023) 15676–15689
- Tunable Wetting of Droplets on Patterned Liquid Surfaces H. Zhao, X. Zhang, J. R. Panter, G. McHale, G. G. Wells, R. Ledesma-Aguilar and H. Kusumaatmaja, (2025), Under review.