LEDs on foil hint at portable water treatment

ENGINEERS at Ohio State University say their success in growing LEDs on sheets of foil opens the field of nanophotonics to industrial-scale production, and the express aim of one day producing portable water treatment systems.

The team used a well-established semiconductor growth technique known as molecular beam epitaxy, in which vaporised elemental materials settle on a surface and self-organise into layers or nanostructures, to grow a ‘carpet’ of nanowire LEDs on pieces of metal foil.

Until now, techniques used by researchers to make nanophotonics have produced small volumes of material and relied on high cost techniques that aren’t scalable on an industrial level.

'People always said that nanophotonics will never be commercially important, because you can't scale them up. Well, now we can,” said Ohio researcher Roberto Myers. “Our research results how you can form UV LEDs directly on metal foil.”

Efforts will now turn to making the technique itself more scalable and industrially-relevant as the researchers seek to enable the development of portable LED-based water purification systems, that emit UV light to kill pathogens. Current techniques require the use of mercury lamps that are bulky and electrically-inefficient, so unsuitable for remote locations with limited power.

“The dream application eventually is that we have UV LEDs that are very efficient and affordable and then you could have portable drinking water production,” Myers told The Chemical Engineer. “That is the motivation behind doing the research. We feel being able to produce UV LEDs cheaply and on a massive scale gets us there sooner.”

The team will now seek to develop a continuous production system.

“Our [current] growth system is expensive – throughput is slow, so wouldn’t scale. That’s why we want to develop a roll-to-roll system where we can have a metal roll going through an evaporation chamber where we deposit the nanowires in a continuous fashion,” he said.

Industry is already using such techniques to make the likes of flexible solar cells, Myers said.
“There are industries that already know how to do this so there is industrial knowledge there. There are routes to take but it will take some work.”

Applied Physics Letters: doi.org/bs5t