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Abstract-
We present a combination of theoretical framework and experimental efforts for
manipulation of flow and particles in microfluidics devices. The key element
of the theoretical framework is the use of time-varying (control) signals to
manipulate matter at micro/nanoscale. The main "process" topics discussed are
mixing and separation. Besides fluidic manipulation, particles in microchannel
devices can also be controlled using electromagnetic forces. A theory of
dielectrophoretic (DEP) particle control is presented, including
multi-frequency actuation methods allowing for efficient separation of
particles that have similar DEP characteristics (such as T-cells and red blood
cells). The joint effects of fluid flow and DEP force are considered and
experimentally observed trapping phenomena explained.
Besides separation and trapping of particles, mixing is a topic that is of
wide interest in microfluidics due to the typically low Reynolds number. A
specific micromixer design is presented, allowing for time-dependent
manipulation of the stream of fluid in the microchannel. A measure of mixing
is introduced that captures effects of stirring, that are dominant in our
small aspect-ratio device. An efficient design is presented, that allows for
millisecond timescale of mixing on micrometer spatial scales.
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