Casting Masters
Masters for casting microfluidic channels are typically made from thin silicon wafers,
and are quite fragile. Moreover, masters tend to lose their patterns over time, and are
difficult to modify to make variations on a single design. Here we demonstrate a
technique for using an existing master to create a new master out of plastic. This new
master is sturdy and can be easily modified (e.g., with wax or modeling clay). Moreover,
multiple plastic masters can be made from a single silicon mapster, allowing each group
of students in the class to have their own master.
The first step is to use the silicon master to cast a PDMS device such as the one shown
below (link goes to larger image). In this case, metal cylinders were used during casting
to create holes for inserting the plastic cylinders.
Rather than bonding the device to a glass slide as shown in the above image, though, the
device is placed in the bottom of a plastic tray channel-side up. A quick-hardening plastic
is poured over the device and allowed to solidify. The plastic takes the complementary
shape to the device; that is, it becomes a new master. The plastic can easily be separated
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