Generation of gradients having complex shapes using microfluidic networks

This paper describes the generation of gradients having complex shapes in s olution using microfluidic networks. Flowing multiple streams of fluid each carrying different concentrations of substances laminarly and side-by-side generated step concentration gradients perpendicular to the direction of t he now. Appropriately designed networks of microchannels for controlled dif fusive during of substances generated a range of shapes for the gradients, including linear, parabolic, rind periodic. The lateral dimensions of the g radients ranged from 900 to 2200 mum. This paper also demonstrates the gene ration of overlapping gradients composed of different species. Since soluti ons in the microfluidic network exist as steady states and are continuously renewed, the gradients established in the capillaries are spatially and te mporally constant and can be maintained easily for periods of hours. Using laminar now to generate gradients should be useful in both biological and n onbiological research.