Inertial Migration of Cancer Cells in a Microfluidic Device - Bioanalysis Advanced Materials Methods and Devices - page 19

2.3 Fabrication of a Polydimethylsiloxane Microchannel
A standard soft lithography technique is widely used for fabricating microchannels
such as those with a stenosis [ 8 ] or with a bifurcation and confluence [ 10 ]. Here, as
an example, we outline the fabrication procedure using photoresist SU-8 and
polydimethylsiloxane (PDMS). SU-8, an epoxy-based photoresist, is widely used
for fabricating channel molds. It can sustain structures with high aspect ratios, so
that vertical sidewalls can be built easily. PDMS is a polymeric silicone with
excellent material properties for making microfluidic devices. Its good optical
transparency, good biocompatibility, accurate replication of fine and complex
geometries, high thermal stability, and low cost make PDMS one of the most
popular materials for microfluidic devices.
Figure 2.2 is a schematic of the procedure used for fabricating the microchannel.
First (Step 1, Fig. 2.2 ) to enhance the adhesiveness of the photoresist on the wafer,
the surface of a silicon wafer was cleaned using piranha solution, which is a mixture
of sulfuric acid and hydrogen peroxide, to remove organic residues. After the
substrate was washed with deionized water to remove all traces of the cleaning
solution, the photoresist (SU-8 2075; Kayaku MicroChem, Tokyo, Japan) was
applied to the silicon wafer with a spin coater. The thickness of the photoresist
was controlled by adjusting the revolving speed of the spin coater (Step 2). Then,
the wafer was glued to a photomask on which the channel geometry had been
drawn. Finally, the wafer was exposed to ultraviolet light (Step 3) completing the
silicon mold with the microchannel pattern (Step 4).
Fig. 2.2 Procedure for fabricating a PDMS microchannel