Design of micromixer and microfludic control system

Micromixer is one of the most significant components of microfluidic systems,
which manifest essential applications in the field of chemistry and biochemistry. Achieving
complete mixing performance at the shortest micro channel length is essential for a
successful micromixer design. We have developed five novel micromixers which have
advantages of high efficiency, simple fabrication, easy integration and ease for mass
production. The design principle is based on the concept of splitting-recombination and
chaotic advection. Numerical models of these micromixers are developed to characterize
the mixing performance. Experiments are also carried out to fabricate the micromixers
and evaluate the mixing performance. Numerical simulation for different parameters such
as fluids properties, inlet velocities and microchannel cross sectional sizes are also
conducted to investigate their effects on the mixing performance. The results show that
critical inlet velocities can be predicted for normal fluid flow in the micromixers. When the inlet velocity is smaller than the critical value, the fluids mixing is dominated by
mechanism of splitting-recombination, otherwise, it is dominated by chaotic advection. If
the micromixer can tolerate higher inlet velocity, the complete mixing length can be further
reduced. Our simulation results will provide valuable information for engineers to design
a micromixer by choosing appropriate geometry to boost mixing performance and broaden
implicational range to fit their specific needs. Accurate and complicated fluidic control,
such as flow mixing or reaction, solution preparation, large scale combination of different
reagents is also important for bio-application of microfluidics. A proposal microfluidic
system is capable of creating 1024 kinds of combination mixtures. The system is composed
of a high density integrated microfluidic chip and control system. The high density
microfluidic chip, which is simply fabricated through soft lithography technique, contains
a pair of 32 flow channels that can be specifically addressed by each 10 actuation channels
based on principle of multiplexor in electronic circuits. The corresponding hardware and
software compose the control system, which can be easy fabricated and modified,
especially for prototype machine developing. Moreover, the control system has general
application. Experiments are conducted to verify the feasibility of this microfluidic system
for multi-optional solution combination.