A picoliter-volume mixer for microfluidic analytical systems

Mixing confluent liquid streams is an important, but difficult operation in microfluidic systems, This paper reports the construction and characteriza tion of a 100-pL mixer for liquids transported by electroosmotic now. Mixin g was achieved in a microfabricated device with multiple intersecting chann els of vat Sing lengths and a bimodal width distribution. All channels runn ing parallel to the direction of now were 5 mum in width whereas larger 27- mum-width channels ran back and forth through the parallel channel network at a 45 degrees angle, The channel network composing the mixer was similar to 10 mum deep. It was observed that little mixing of the confluent solvent streams occurred in the 100-mum-wide, 300-mum-long mixer inlet channel whe re mixing would be achieved almost exclusively by diffusion, In contrast, a fter passage through the channel network in the similar to 200-mum-length s tatic mixer bed, mixing was complete as determined by confocal microscopy a nd CCD detection, Theoretical simulations were also performed in an attempt to describe the extent of mixing in microfabricated systems.