Nano-fridge

It is relatively easy to heat up chemical and biological samples on a tiny scale but cooling them down again is a much harder task.Both heating and cooling on the micro-scale are important if you want to build a fully functional lab-on-a-chip device, as many teams around the world are trying to do. So researchers at Caltech in Pasadena, US, have come up with a method that involves evaporative cooling – the same process that keeps our bodies cool when we sweat.On a large scale, evaporative cooling is a straightforward process. But on the nanolitre-scale envisaged for lab-on-a-chip work, it is much harder because, on smaller scales, liquids and gases do not to mix as well, making evaporation much more difficult.The researchers' invention is a y-shaped tube in which a liquid coolant, such as diethylether, is fed into one arm of the Y-tube, while compressed nitrogen is fed into another. At the junction, the gas and liquid mix and the diethylether evaporates, absorbing heat, which the mixture then carries away through the third tube. The team says the technique could one day be used to cool advanced computer chips.