MIXING two liquids together might sound simple, but for engineers designing a new generation of microchip-sized laboratories this apparently straightforward task has become a major headache. However a new technique offers a simple, cheap and elegant solution.
Fluids behave differently on a micro scale: the absence of convection in minuscule pipes dramatically slows down the mixing process, and diffusion is far too slow to be useful. In the past, engineers have used complex, expensive, micrometre-sized mechanical mixers to do the job. Tiny motors on the chips drive mixing vanes, but they are costly, unreliable and can easily gum up.
But…
