Integrating different steps on a chip for cell manipulations and sample preparation
is of foremost importance to fully take advantage of microfluidic possibilities, and
therefore make tests faster, cheaper and more accurate. We demonstrated particle
manipulation in an integrated microfluidic device by applying hydrodynamic,
electroosmotic (EO), electrophoretic (EP), and dielectrophoretic (DEP) forces. The
process involves generation of fluid flow by pressure difference, particle trapping
by DEP force, and particle redirect by EO and EP forces. Both DC and AC signals
were applied, taking advantages of DC EP, EO and AC DEP for on-chip particle
manipulation. Since different types of particles respond differently to these signals,
variations of DC and AC signals are capable to handle complex and highly variable
colloidal and biological samples. The proposed technique can operate in a highthroughput
manner with thirteen independent channels in radial directions for
enrichment and separation in microfluidic chip. We evaluated our approach by
collecting Polystyrene particles, yeast cells, and E. coli bacteria, which respond
differently to electric field gradient. Live and dead yeast cells were separated
successfully, validating the capability of our device to separate highly similar cells.
Our results showed that this technique could achieve fast pre-concentration of
colloidal particles and cells and separation of cells depending on their vitality.
Hydrodynamic, DC electrophoretic and DC electroosmotic forces were used
together instead of syringe pump to achieve sufficient fluid flow and particle
mobility for particle trapping and sorting. By eliminating bulky mechanical pumps,
this new technique has wide applications for in situ detection and analysis.