Inertial Migration of Cancer Cells in a Microfluidic Device - Bioanalysis Advanced Materials Methods and Devices - page 20

Fig. 2.3 Experimental setup: ( a ) schematic representation of the experimental setup; and ( b )
Geometry of PDMS microchannel. The height of the channel is 220 m m[ 22 ]

PDMS (Silpot 184; Dow Corning, Midland, MI) was prepared (Step 5) by
mixing the base compound and curing agent at a weight ratio of 10:1. After
removing the bubbles created during mixing, the mixture was poured on the
master mold and cured by baking for about 40 min at 85 C. The PDMS was
peeled (Step 6) from the master, and the fluidic ports used as the inlets and outlets
of the fluidic device were created using a biopsy punch (Kai Industries, Gifu,
Japan). For channels with very fine patterns, it is sometimes difficult to peel the
PDMS channel from the master mold. In such cases, mold release agents are
useful. Finally, to prevent fluid leakage from the gap between the PDMS and glass
slide, an oxygen plasma treatment was applied (Step 7) to irreversibly bind (Step
8) the PDMS to the glass. Each step is straightforward, although special facilities
are necessary, including a clean room and photolithography equipment. Alterna-
tively, a private company may be contracted to fabricate the PDMS microchannel.
In Sects. 2.5 and 2.6, we use a simple microchannel (cf. Fig. 2.3b ) made using this
technique.

2.4 Cell Preparation and Working Fluids

This section explains the preparation of cells and sample fluids used to perform
the experiments in Sects. 2.5 and 2.6. The poorly differentiated human breast
cancer cell line MDA-MB-231 was used. The cells in RPMI 1640 (Invitrogen,