Author(s): Bernhard H Weigl, Paul Yager
Most fluids show laminar behavior in miniature flow structures with channel cross-sections below 0.5 mm. Different layers of miscible fluids and particles can flow next to each other in a microchannel without any mixing other than by diffusion. Small particles diffuse faster than larger ones, which allows separation of particles by size. It is possible to design fluidic microchips in which separations, chemical reactions, and calibration-free analytical measurements can be performed directly in very small quantities of complex samples such as whole blood and contaminated environmental samples.