The Microfabrication group of Aalto University has developed a new and rapid method for fabricating non-reflecting and self-cleaning surfaces, which they say will speed up the fabrication process.
The method for fabricating pyramid-shaped nanostructures on a silicon surface uses deep reactive ion etching. The nanostructured silicon wafer can be further used as a template, which can be used to replicate the original non-reflective and self-cleaning nanostructure into the different polymers.
Smooth silicon surfaces are mirror-like and reflect more than 50 per cent of incoming light, while nanostructured silicon and polymeric surfaces are almost completely non-reflecting. The reflectance is reduced at broad wavelength range due to smooth refractive index transition from air to substrate because of the nanostructures, says Lauri Sainiemi from Microfabrication group.
Non-reflecting surfaces and their fabrication are of interest because they are needed to make solar cells more efficient. In addition, the surfaces are self-cleaning.
Potential applications of the nanofabrication methods for silicon and polymers range from sensors to solar cells. The researchers say the greatest strength of their fabrication methods is its scalability, which will enable simple and low-cost manufacturing of nanostructures on a large scale. The techniques are compatible with single-crystalline, poly-crystalline and amorphous silicon, as well as wide variety of different polymers.
The group has already developed surfaces for chemical analysis of drugs in collaboration with other research groups and that research will continue in future. An interesting novel field is the development of more effective self-cleaning and dirt-repellant surfaces that would especially benefit solar cell research. The fabrication of water-repellent surfaces is fairly straightforward, but liquids with low surface tension can still contaminate the surface. At the moment they are developing novel surfaces that also repel oily liquids.
ReferencesNon-Reflecting Silicon and Polymer Surfaces by Plasma Etching and Replication
Sainiemi, L. et al.
Advanced Materials on line, 27 Oct 2010