Hi there, it’s Christian again. This time I want to talk about my secondment experience. The 1 month long secondment at the FHNW (University of Applied Sciences and Arts Northwestern Switzerland) was split apart in two blocks of two weeks.
I decided to do some joint work with Dian Haasbroek (ESR7) who is also going to come for his secondment to the UT. Together with him, we developed a planning for the secondment with discussing the results with our supervisors. Without going into too much detail, our goal was to create nanostructures in form of nanoripples on polymers. We decided to continue to produce nanostructures – known as LIPSS (laser-induced periodic surface structures) – on his type of polymer of his interest (polyimide, PI) areawide and replicate them onto the polymer of my interest (cyclic olefine copolymer, COC) as it is challenging to create such areas of nanostructures directly on my polymer. Eventually, some promising results are obtained as you can see in the microscope picture. The color change here has the same cause as the colors of some butterflies: While some butterflies have pigments for their wings, some other butterflies have periodic nanostructures so that the color changes with the incident of light and only one certain color is being reflected backwards. The effect is know as optical diffraction. So, my research is blessed looking at these colorful areas which may have applications e.g., for marking. However, our main goals are not to change the color of the sample but to change the wettability of the surface. By micro- and nanostructuring the surface, you can change the how water behaves on the surface. Either it becomes more hydrophilic so that you can guide water into intended directions or, you can make it more hydrophobic so that you water is repelled from the surface making the surface cleaner. These two behaviors are also observed in nature: Certain bugs have hydrophilic structures which collects water from the humidity in drier regions and guide the collected water into their mouths. Some plants on the opposite can use hydrophobic structures to keep the surface of their leaves clean – known as the lotus leaf effect.
Left: A look through a microscope looking at an areawide LIPSS (laser-induced periodic surface structures) textured surface noticing the change of its structural color. Right: Image from a laser scanning microscope looking at LIPSS. They have periodicities of around 200nm.
It’s a pity in my view that time ran off too fast so we couldn’t finish all our ambiguous goals. But at least, we can continue our different researches and include these results. One challenge here may be to agree on how exactly the results are going to be exploited now so that all interests of the parties involved are satisfied. But after experiencing the collaboration together with Dian and our supervisors, I’m positive that we will manage. I enjoyed the collaboration and I’m looking forward to the next collaborations with Chayan (ESR10) at Micronit and with Myka (ESR5) who will come to the UT. In the meanwhile, I’m going to look at the contact angles and roll-of-angles of fluids to determine the wettability of the surface. Also, I continue to get some LIPSS nanostructures directly on COC so that the molding step can be skipped.
One nice day in Zürich. If you visit another country, maybe scouting the area around in your free time is a good idea 😉
