Membranes that alternately block the passage of gases and then allow them to flow through are a crucial part of many engineering processes, but we've never found a perfect switch to let the gases through - until we used light.
The ability to control the movement of gas is vital in many experiments, but until now the only ways to control the membrane - and, thus, the gases - involved heat and electricity, both of which had significant drawbacks. But now researchers at the University of Rochester have figured out how to change the membrane's structure using two different forms of light, opening up unprecedented engineering applications.
Here's how this new membrane works. It's made from hard plastic, which is then punctured with lots of little holes. These holes are filled with liquid crystals and dye. When a purple light is directed towards the membrane, the dye molecules become straight, forcing the liquid crystals into regular patterns that provides plenty of space for the gas to flow through freely. When the purple light is replaced with an ultraviolet one, the dye molecules twist into a banana-like shape, which scatters the liquid crystals and blocks the passage of gas through the tunnel.
This innovation offers a lot of advantages over the old heat- and electricity-based designs. The light fixtures can operate remotely without any hard connection to the membrane, which isn't possible when you need to attach something like electrical lines. This opens the door to much smaller, more simplified setups than were previously possible. Speaking of smaller, light also has a positively tiny energy requirement, needing little more power than what it takes to switch on the lamps.
Light also provides significantly more control than heat or electricity. While light can be altered precisely and pretty much instantaneously, it takes a long time to heat up or cool down a membrane, and repeated temperature changes can damage the membrane over time. Finally - and this is a very big deal when working with hydrocarbons and other flammable gases - it's impossible for light to ignite the gas, which greatly reduces the safety measures that need to be taken when working with such materials.