Year/Course: 2013-2014, Lent 2014
Mentor: Paul May

Contact: Professor Ulli Steiner, Physics
Mentor: Paul May

The research team has been working on anti-reflective coatings for more than 10 years. Although such coatings are widely used already, they decided to investigate them from a physicist’s perspective to try to design more optimal coatings which have good optical properties and are mechanically robust.

Current coatings consist of compact layers of low-refractive index transparent materials that are vacuum deposited. While wide-spread, they are not optimal in their optical performance , relatively expensive to make and cost-effective only for small surfaces such as eye-glasses and certain optical elements. Other approaches are based on porous thin layers that can either be made from  polymers which give good optical results but are mechanically fragile, or porous inorganic materials which are physically strong but get clogged easily with dirt, resulting in changes to the optical properties.  Since we are nowadays surrounded by glass and plastic screens, covers and windows, there many other products might benefit from a low-cost anti-reflective coating technology that is easy to apply.

The team’s solution is to use transparent inorganic materials to make a porous layer, that is more porous than is needed to achieve the required refractive index. Titanium dioxide nano crystals are then incorporated into the coating. This has two effects – firstly the TiO2 acts as a catalyst to break down dirt from the surface, and secondly it raises the refractive index of the coating to give the desired level of anti-reflectivity.

The new coating has been shown to be reasonably robust, self-cleaning when exposed to UV light, and anti-reflective. When used on plastics it can enhance the surface strength. In addition the materials are inexpensive and are conceptually cheap to apply, since the coating can be applied using standard liquid coating techniques. This means that it may work on much larger glass and plastic surfaces than existing coatings.

The challenge for the i-Team is to investigate the different markets which need anti-reflective coatings, including those that currently use such coatings, and those that do not, by talking to industry experts and gathering feedback and ideas. They will then analyse the feedback from these industries and recommend the best commercial direction for the researchers going forward.