Diffusion along microfluidic channels

Living cells respond simultaneously to a variety of different stimuli. Inside the cell the information emanating from different receptors is processed and integrated in molecular networks. For the specific modulation of such networks mixtures of stimuli or agents interfering with molecular activities are required. However, in order to identify optimum mixtures with respect to the identity of compounds and relative and absolute concentrations, large numbers of biological tests are required. Diffusion represents a highly efficient means for the generation of substance mixtures with a minimum of pipetting steps. Here, we present an array of microfluidic channels for the generation of substance mixtures with only two pipetting steps. A microfluidic structure with a height of 500 mu m was fabricated. Diffusion was observed by fluorescence microscopy for fluorescein dissolved in water and the diffusion constant determined. Furthermore, a procedure to detect unwanted flow in the channels is developed. (c) 2006 Elsevier B.V. All rights reserved.