SU-8 microchannels for live cell dielectrophoresis improvements

In this work a novel SU-8 fabrication technology is employed to construct microfluidic devices for sensitive dielectrophoretic (DEP) manipulation of budding yeast cells. Identical devices were produced with standard soft-lithography processes. In comparison to standard PDMS based soft-lithography, an SU-8 layer was used to construct the microchannel walls sealed by a flat sheet of PDMS to obtain the microfluidic channels. Direct bonding of PDMS to SU-8 surface was achieved by efficient wet chemical silanization combined with oxygen plasma treatment of the contact surface. The presented fabrication process significantly improved the alignment of the microstructures. In addition, PDMS delamination above electrode topologies was significantly decreased over standard soft-lithography devices. The fabrication time and costs of the proposed methodology were found to be roughly the same. Sensitivity of the devices was tested by discriminating Saccharomyces cerevisiae cells in the G1 phase from cells in the S/G2/M phase using dielectrophoresis. This level of sensitivity necessitated high precision electrode structure that was designed using an FEM model based approach. Attaining such high precision using standard soft-lithography can be difficult due to additional requirements of an alignment stage and its associated tight timing limits.