Sheathless Dielectrophoresis-Based Microfluidic Chip for Label-Free Bio-Particle Focusing and Separation

Abstract

This paper presents a novel microfluidic dielectrophoresis (DEP) system to focus and separate cells of similar size based on their structural differences, which is more challenging than separation by size. Because, in this case, the DEP force is only proportional to the polarizabilities of cells, we used live and dead yeast cells as bio-particles to investigate the chip efficiency. Our designed chip consists of three sections. First, we focused on cells at the center of the microchannel by employing a negative DEP phenomenon. After that, cells were separated due to the different deflection from high-electric-field areas. Finally, a novel outlet design was utilized to facilitate separation by increasing the gap between the two groups of cells. The proposed sheath-free design has one inlet for target cell injection requiring only one pump to control the flow rate, which reduces costs and complexity. Successful discrimination of the particles was achieved by using DEP force as a label-free and highly efficient technique. As an accessible and cost-effective method, soft lithography with a 3D-printed resin mold was used to fabricate the microfluidic parts. The microchannel was made of polydimethylsiloxane (PDMS) material that is biocompatible. The electrodes were made of gold due to its biocompatibility and non-oxidation, and a titanium layer was sputtered as the buffer layer for the adhesion of the sputtered gold layer to the glass. A standard microfabrication process was employed to create the electrode pattern. O2 plasma treatment yielded leakage-free bonding between the patterned glass and PDMS structure containing the microfluidic channel. The maximum voltage applied to the electrodes (26 V) was lower than the threshold value for cell electroporation. The simulations and experimental results both confirm the effectiveness of the proposed microfluidic chip.

Keywords

• dielectrophoresis
• microfluidics
• planar electrodes
• cell separation
• active focusing