Optical plastic lenses with super-hydrophobic surface

Initial successes in the polyoptics’ research project: Optical plastic lenses with super-hydrophobic surface

The use of optical lenses with conventional surface texture entails certain disadvantages in some applications:

For example, the use of optical components in areas with high dust content (e.g. mining) would cause a risk of scratching the lenses during the cleaning process; When using lenses in poorly accessible outdoor areas (e.g. street lighting), moss will form on the surface in the long term, etc.

In these and many other areas of application, a self-cleaning capacity of the optics would bring a significant benefit.
But also, in the field of medical technology, the development of lenses with super-hydrophobic surface structure would be an enormous breakthrough, for example in the use of lab-on chips, in which both super-hydrophobic and super-hydrophilic zones are arranged side by side on a chip in order to keep various test fluids such as blood on a spot and wetting them perfectly.

The aim of a research project by polyoptics was therefore to develop a process chain with the help of which super-hydrophobic, that means extremely water-repellent optical lenses, can be produced directly from the tool – i.e. without the need for an additional coating.

Test platelets with superhydrophobic surface

Test platelets with superhydrophobic surface

SEM shot of used nanograss-structures

SEM shot of used nanograss-structures
Photo Source: NIL Technology Denmark

The functionality of these lenses is thereby created via a nanostructure applied to the surface. This nanoimprint technique is a technique already used in the semiconductor industry. By transferring the layers to nickel shims it has been developed for the use in plastics industry as well.
This technique allows small surface structures to be applied in a controlled manner. In the optical industry, such nanostructures serve to give the surfaces functional characteristics (e.g. moth eye structures as an anti-reflective layer by plasma etching [IOF Jena]).

Although the plastics centre in Leipzig had already succeeded in producing superhydrophobic surface properties directly from the tool before the beginning of the project, its structures were in the order of 5μm, so that it was not possible to manufacture clear and transparent optics.
In order for structures to be usable on optical components, structural sizes below 200nm are required, otherwise the structures will not be invisible or transparent.

Contact angle water on topas5013L10platelets: 130°

Contact angle water on topas5013L10platelets: 130°

In the course of the research project, polyoptics managed to reduce the structures that produce the super-hydrophobic properties from around 5μm in size to well below 1μm [approximately 400nm were reached].
This has already enabled polyoptics to reach its first milestone, as such structural sizes allow to be applied in infrared optics.
However, to make super-hydrophobic structures for optical components in the visible area available directly from the tool, further research is still needed.

polyoptics GmbH is happy to rise to this challenge in order to provide further contributions in this field of research and to create innovations for the markets mentioned above.
Achieving this goal would also make it possible to add additional structures that, for example, have anti-reflex or anti-scratch properties. Already, polyoptics is also active in this field of research and sensor technology, because this new technology offers the company a perfect complement to its long-standing coating expertise and thus opens completely new possibilities to fulfill individual customized wishes.