Solid-state controllable light filter may protect preterm infants from disturbing light

Now, in a paper accepted for publication in Applied Physics Letters, a journal of the American Institute of Physics, researchers describe a proof-of-concept mirror that switches between reflective and red-transparent states when a small voltage is applied.

The research team had previously identified a magnesium-iridium reflective thin film that transforms into a red-transparent state when it incorporates protons. Providing those protons in a way that is practical for preterm incubators, however, was the challenge. The typical method--using dilute hydrogen gas--is unacceptable in a hospital setting. So the team created a stack of thin films that includes both an ion storage layer and the magnesium-iridium layer: a voltage drives protons from the ion storage layer to the magnesium-iridium layer, transforming it into its red-transparent state. Reversing the voltage transforms it back into a reflective mirror.

The researchers report that the device still allows some undesirable light wavelengths through, but a force of just 5 V changes the device's state in as little as 10 seconds. The researchers are now looking at other materials to improve color filtering and switching speed.