Central heating for microdevices

Ionic liquids provide new temperature controls.

A heating process notorious for causing problems in analytical chemistry has been used as a simple method for controlling temperature in microfluidic channels. Joule heating happens when an electric current flows through a conducting liquid and heats the liquid it passes through. The effect causes problems such as band broadening and bubble formation in capillary electrophoresis and electroosmotic flow systems.

Now, Andrew de Mello and colleagues at Imperial College London, UK, have exploited the effect in ionic liquids to control precisely the temperature of localised areas in microfluidic chips. By applying alternating current to an ionic liquid in a channel parallel to one requiring heating, specific areas of a microfluidic system can be controllably heated. Heating can be fast or slow, depending on the voltage applied, and the easily-fabricated microdevices are completely transparent, making it easy to view samples. The team expects the approach to be particularly useful in applications where temperature cycling is needed, such as polymerase chain reactions.

Rowena Milan