Diffusion-based extraction in a microfabricated device

Microfabricated fluid systems allow complex chemical analyses to be performed on sub-nanoliter volumes. However, many common laboratory procedures, including filtration, have yet to be robustly implemented in micro-fluid systems. A device has been developed to separate particles and molecules based on their diffusion coefficients; the process is demonstrated using a micromachined device with fluid channels as small as 20 mu m. A simple model predicts exponential dependence of the output concentration on diffusion coefficient in certain regimes. Experiments confirm the model.