For the first time, scientists have used ultra violet light emitting diodes (UV-LEDs) to make polymer columns in lab-on-a-chip devices. The columns could be used as micropumps to move ions through the devices, claim Mirek Macka at Dublin City University, Ireland, and colleagues in Ireland and the Czech Republic.

The team used the light from UV-LEDs to start a polymerisation reaction between methacrylate units inside the channels of a microfluidic chip. They found that channels containing the resulting polymer columns were better at pumping ions than bare channels when they applied an electric field to the chip.

LEDs are solid-state light sources, where electrical energy is converted to light in a semiconductor material. Although conventional UV light sources, such as xenon arc lamps, can be used in photopolymerisation reactions, UV-LEDs offer a number of advantages: they are much smaller and can be used in miniature devices; they use less energy; and they are cheaper.

At present, commercially available UV-LEDs have poor electric energy-to-light conversion, which in turn can generate a lot of heat. 'Further development and improvement of the technical parameters is needed for UV-LEDs to become really attractive for mainstream chemistry,' says Macka. He plans to use UV-LEDs to photocatalyse other reactions to investigate their versatility, compared with classical UV sources.

Michael Brown