Butterfly wings used to print self-cleaning windows

Any child can make a butterfly print, but doing so on an industrial scale is far from child's play.

Butterfly wings - and lotus leaves - are able to repel water with ease because of the microstructures on their surface. The densely packed microscopic bumps of the lotus leaf and the waffle-like structures found on butterfly wings both make it difficult for water droplets to spread out. As a result, the drops roll off, and they take dirt with them. This makes the surfaces ideal as the basis for self-cleaning windows and windshields.

Butterfly wings are able to repel water with ease because of the microstructures on their surface

However, creating such surfaces is tough because it means creating a template using lithographic techniques usually reserved for chip making. This makes it costly and slow, and limits the size of surfaces that can be produced, says Christophe Peroz at the French National Centre for Scientific Research in Aubervilliers.

So he and his colleagues developed a cheaper and quicker technique that involves pouring a silicon-based polymer liquid over an actual wing or leaf and leaving it to dry. They then peeled off the solid polymer and used it as a mould for methyltriethoxysilane (MTEOS) - an agent used in glass-making which can be changed from a liquid to a gel by spinning it. The MTEOS is poured onto the mould and spun, forming a 900-nanometre-thick film (Bioinspiration and Biomimetics, DOI: 10.1088/1748-3182/3/4/046004).

To create a large water-repellent surface for a window, for example, many films can be combined.