We present a continuous-flow active micromixer based on channel-wall deflection in a polydimethylsiloxane (PDMS) chip for volume flows in the range up to 2？μL s ？1 which is intended as a novel unit operation for the microfluidic Braille pin actuated platform. The chip design comprises a main microchannel connected to a series of side channels with dead ends aligned on the Braille pins. Computer-controlled deflection of the side-channel walls induces chaotic advection in the main-channel, which substantially accelerates mixing in low-Reynolds number flow. Sufficient mixing (mixing index MI below 0.1) of volume flows up to 0.5 μL s ？1 could be achieved within residence times ~500 ms in the micromixer. As an application, continuous dilution of a yeast cell sample by a ratio down to 1:10 was successfully demonstrated. The mixer is intended to serve as a component of bio-analytical devices or as a unit operation in the microfluidic Braille pin actuated platform.
Lee, Y.K.; Deval, J.; Tabeling, P.; Ho, C.M. Chaotic mixing in electrokinetically and pressure driven micro flows. In Proceedings of the 14th IEEE International Conference on Micro Electro Mechanical Systems, Interlaken, Switzerland, 21–25 January 2001; pp. 483–486.