Microfluidic devices with tunable microtopographies

Microfluidic devices are critical components of many biomedical and bioanalytical instruments and allow for probing chemical and physical phenomena at the micron scale. Most current microfluidic devices, however, have the inherent functional limitation that the cross-sectional channel geometry, which determines the fluid flow patterns, is essentially constant at any given point in the channel. We present microfluidic channels that contain topographical features whose size can be tuned by the user in real time. We demonstrate that the topographical changes can be used to alter the laminar flow patterns in microfluidic mixers and to physically trap small fluid volumes. (C) 2005 American Institute of Physics.