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 high-throughput 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.
The authors acknowledge the financial support provided by the Hong Kong Research Grants Council Grant No. HKUST604710, 605411. This publication was based on work partially supported by Award No. SA-C0040/UK-C0016 made by King Abdullah University of Science and Technology (KAUST).
III. MATERIALS AND EXPERIMENTS
A. Preparation of particle suspensions and experiment setup
B. Fabrication and design of multilayer microfluidic chip
IV. RESULTS AND DISCUSSIONS
A. Characteristics of designed electrode
B. Particles and cells choice
C. Trapping of PS particles
D. Collection and release of yeast cells
E. E. coli capture
F. Separation of live and dead yeast cells
V. CONCLUSIONS AND PERSPECTIVES
- Biological electrophoresis
- Electric fields
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