Researchers at the University of Lille in France have demonstrated a microelectromechanical system (MEMS) that can be turned on using ordinary white light. As a proof of concept, the researchers have built a miniature switch that can be controlled using light from almost any distance, be it from a flashlight or the sun.

This “actuation at a distance” utilizes a recently-discovered effect called photoelectrowetting. Electrowetting is an effect that changes the hydrophobicity of a material by applying a voltage — photoelectrowetting is the same thing, but where photons trigger the switch. Basically, the more hydrophobic a material is, the “higher” a water droplet rises from the material, because it is being pushed away. On materials with low hydrophobocity, water droplets are very thin. If you’ve ever seen how water droplets form on a waxed car or a non-stick pan, versus a big puddle of Coke or coffee on your desk, that’s the same thing. The picture below might help you visualize this.

To harness this new effect, Steve Arscott and Matthieu Gaude created a semiconductor device that’s a lot like a capacitor — two conducting electrodes separated by an insulator — but in this case, the insulator is a thin layer of Teflon and a drop of water. The top electrode is cantilevered so that it wants to fall on the bottom electrode to create a circuit, but the droplet of water holds it up. When light hits the device, however, photoelectrowetting reduces the water’s thickness, the electrodes move closer, and a circuit is formed: Voila, a tiny, light-actuated switch.

You’re probably already thinking of the possible applications, but let me throw in a few more. First, this microelectromechanical system uses almost zero power — it has to have a power source, but only to provide a voltage differential between the electrodes; almost the entirety of the energy used comes from the light. This means that you can have autonomous, wireless sensors almost anywhere you like. By far the most difficult part of creating sensor networks is connecting it all up to provide power and addressing; this discovery means you can effectively turn a device on at the end of your garden by flashing a light at it.

Second, this will probably pan out to be an important discovery for the fast-growing field of silicon labs-on-a-chip (LoC). Such great strides have been made in the realm of microfluidics — controlling fluids using microelectromechanical systems — that we now have cheap LoCs that can decode a complete DNA genome in a few hours. Any effect that results in greater automation at a nano scale has to be a good thing — until the Singularity, anyway.

Read more at arXiv.org (research paper)