Bacterial cell sorting in microchannels

Microfluidic devices offer exciting prospects for the identification, sorting and manipulation of microorganisms. Devices featuring microchannel arrays or patterned surfaces with specific cellular interactions are expected to have a broad range of biomedical, environmental and security applications; e.g. surface modification or use of chemical repellents in dental implants to impart them with resistance to plaque formation. In this paper, we present experimental measurements and modeling studies of the migration of motile chemotactic bacteria in porous channels. Chemotaxis refers to the ability of microorganisms to bias their movement in response to detected chemical gradients of nutrients, pH, dissolved oxygen and other substances. Motile chemotactic organisms distribute to regions of high attractant concentration much more rapidly than their nonchemotactic or nonmotile counterparts. This sensitivity can be exploited in the fabrication of microchannel devices to sort and identify bacterial species and to control the regions where biofilm growth occurs on porous substrates. The migration of bacteria in porous media has been simulated for E. coli and P. stutzeri under conditions in which the cells respond chemotactically to chemical gradients that arise from consumption of nutrients that also act as chemoattractants. The results of the simulations reveal an enhanced motility of the chemotactic cells through porous media relative to their bulk solution phase chemotaxis. Simulation results and experimental visualizations are presented for cell migration through porous media constructs and laser ablated microchannels in glass substrates.