A team from the Department of Chemistry at Imperial College London have created a material that has tiny scales that can be "accurately controlled" and are only tens of nanometres in size.
It works by using gold nanoparticles to "localise at the interface between two liquids" that won't mix.
Study co-author Professor Joshua Edel, from the Department of Chemistry at Imperial, said: "It's a really fine balance - for a long time we could only get the nanoparticles to clump together when they assembled, rather than being accurately spaced out. But many models and experiments have brought us to the point where we can create a truly tuneable layer."
Whilst study co-author Professor Alexei Kornyshev, from the Department of Chemistry at Imperial, added: "Finding the correct conditions to achieve reversibility required fine theory; otherwise it would have been like searching for a needle in a haystack. It was remarkable how closely the theory matched experimental results."
When a small voltage is applied, the layer is able to go from being dense or sparse, which means it can switch between a reflective mirror surface and a transparent one.
Co-author Professor Anthony Kucernak, also from the Department of Chemistry, shared: "Putting theory into practice can be difficult, as one always has to be aware of material stability limits, so finding the correct electrochemical conditions under which the effect could occur was challenging."
With Professor Kornyshev adding: "The whole project was only made possible by the unique knowhow and abilities and enthusiasm of the young team members, including Dr Yunuen Montelongo and Dr Debarata Sikdar, amongst others who all have diverse expertise and backgrounds."