Teacher : Cheng-Hsien Liu Student : Chien-Yu Chen(陳鍵瑜) LATERAL CELL SEPARATION IN MICROFLUIDIC CHANNEL BY 3D ELECTRODE DIELECTROPHORESIS Teacher : Cheng-Hsien Liu Student : Chien-Yu Chen(陳鍵瑜) Date : 06/20/2007 Reference : μTAS2006, p.567-569 Chien-Yu Chen MSCL

Outline Introduction Design & simulation Fabrication Experiment results Conclusion Chien-Yu Chen MSCL

Introduction Dielectrophoresis (DEP) : determined by frequency Positive DEP Negative DEP Most of current DEP electrodes utilize planar electrodes on the surface of the substrate to generate DEP force. The electric field decays exponentially with the height of the channel for the planar electrode configuration Chien-Yu Chen MSCL

Design concept Inlet 3-D vertical electrode Outlet The force balance plot of the cells in the separation zone. Chien-Yu Chen MSCL

Simulation：side-wall vertical electrodes Planar electrodes at bottom of channel. (b) Trapezoidal channel from silicon wet etching. (c) Electrodes embedded in the vertical side wall of the channel. Electrodes at the side walls produce uniform field in the Chien-Yu Chen MSCL

Simulation：electrical field gradient The center of the channel： minimum electrical field. Close to the electrodes： maximum electrical field. Chien-Yu Chen MSCL

Fabrication The curvature of the channel top surface from the previous lithography step makes it difficult for the rigid glass cover slip to seal the channel. The flexible PDMS sheet can conformably seal the channels. Chien-Yu Chen MSCL

DEP forces The equilibrium points (zero DEP The equilibrium points (zero DEP forces) of two objects with different polarization factors can be tuned to away from the center as shown by the dashed line. Chien-Yu Chen MSCL

Experiment result : fabrication The final channel with electrodes embedded in the sidewall. SEM of vertical electrode before channel layer is constructed. Chien-Yu Chen MSCL

Experiment result : separation method1: both electrodes are turned on Cells (white circles) are sorted to top channel outlet and beads (black circles) are sorted to bottom outlet. Left : free flow without DEP forces. Right : with DEP separation. Chien-Yu Chen MSCL

Experiment result : separation method2: only top electrode are turned on N115 cells repelled from the top electrodes and flow into the bottom channel. HEK293 cells are released from the top electrodes and flow into the top channel. Chien-Yu Chen MSCL

Conclusion Advantage: Vertical electrodes in the side wall of the micro-channels to generate electric field. The electrical field can extend to the entire channel space to avoid any dead electrical field region. Continuous flow through separation system enables high throughput microfluidic sorting. Disadvantage: Need to find the frequencies to fit the two kinds of cells/beads simultaneously. Only two kinds of cells/beads can be separated in the meantime. Only a small amount of cells/beads can be separated. Chien-Yu Chen MSCL

Thank you ! Chien-Yu Chen MSCL

Other references : Side-Wall Vertical Electrodes for Lateral Field Microfluidic Applications, Lisen Wang, Lisa Flanagan, and Abraham P. Lee, 2007 IEEE. Chien-Yu Chen MSCL