Special surface: oil dirt removes itself
Researchers at Aalto University, Finland, have developed oil-repellent surfaces with special microstructures on which oil droplets move in a predetermined direction all by themselves. Using this process, it is now possible for oil contamination to remove itself from analytical equipment. Of more general interest could also be the research approach of transporting small quantities of liquid without the need for large amounts of energy.
"We have developed surfaces that can move oil droplets using their surface tension," explains Ville Jokinen, materials scientist.
"We have developed surfaces that can move oil droplets using surface tension," explains Ville Jokinen, a postdoctoral researcher in materials science at Aalto University. Specifically, any droplet that hits anywhere on the microstructure pattern would move towards its centre. This works because it is a special asymmetric geometric pattern on the surface.
New surface tension
"Until now, self-motion of oil droplets was a great challenge due to their low surface tension," emphasizes Xuelin Tian, also a materials science postdoc. For liquids with high surface tension, such as water in particular, it is noticeably easier to achieve similar effects. This is also more common in nature. For example, there are cacti whose needles conduct water in a certain direction according to this principle, and beetles whose shells can do something similar.
Technically very attractive
The new surfaces make not only oil but also various other liquids such as water, wine or pure ethanol move on their own. This is technically attractive, for example, for laboratory instruments that work with small amounts of liquid. "The droplets position themselves very precisely in the center of the pattern. This could be used to apply arrays of functional materials," also says physics professor Robin Ras.
According to him, it is also conceivable to practically reverse the effect and thus ensure that unwanted drops stay away from certain areas of a device - for example, so that the nozzles of inkjet printers do not stick.
