Unique light-activated membrane that acts like a traffic signal for gas

WASHINGTON - Scientists have developed first of its kind membrane that blocks gas from flowing through it when one colour of light is shined on its surface, and permits gas to flow through when another colour of light is used.

The membrane is a piece of hard plastic riddled with tiny holes that are filled with liquid crystals and a dye.

When purple light illuminates the surface of the membrane, the dye molecules straighten out and the liquid crystals fall into line, which allows gas to easily flow through the holes.

But when ultraviolet light illuminates the surface, the dye molecules bend into a banana shape and the liquid crystals scatter into random orientations, clogging the tunnel and blocking gas from penetrating.

Eric Glowacki, a graduate student at the University’s Laboratory for Laser Energetics, and Kenneth Marshall, his advisor, invented the membrane.

Controlling a membrane’s permeability with light is preferable to controlling it with heat or electricity - two readily used alternative methods - for several reasons, Glowacki said.

For starters, light can operate remotely. Instead of attaching electrical lines to the membrane, a lamp or a laser can be directed at the membrane from a distance.

This could allow engineers to make much smaller, simpler setups.

Another advantage is that the colour of the light illuminating the membrane can be changed precisely and almost instantaneously. Other methods, like heating and cooling, take a relatively long time and repeated heating and cooling can damage the membrane.

Also, light does not have the potential to ignite a gas, which could be a crucial benefit when working with hydrocarbons or other flammable gases.

Lastly, the amount of light energy needed to switch the membrane on and off is miniscule.

The membrane could be useful in controlled drug delivery and industrial processing tasks that require the ability to turn the flow of gas on and off as well as in research applications.

The findings were presented at the International Society for Optics and Photonics (SPIE) in San Diego. (ANI)