7 Assembly
It is necessary to carefully remove all segments of PSA and PMMA that have been
cut from the main disk layer, this is done by hand prior to entering the clean room. If
left in place these small pieces of PSA and PMMA may interfere with the flow of
fluid through the microchannels of the disk during testing (Fig.5.20).
A custom built alignment housing is used to ensure that that the disks are aligned
accurately when assembled, due to the microfluidic nature of the Lab-on-a-disk
platform even the smallest deviation during assembly can destroy the functionality
of the device. Figure5.21shows how this custom assembly jig is used to guide the
assembly of the disk. It is for this same reason that assembly is completed within a
clean room environment as small particles of dust may inhibit the flow within the
device.
As previously stated the PSA serves a dual purpose in the construction and
functionality of the disk, it provides channels of narrow dimensions for fluid to pass
from one chamber to the next however it also acts as the adhesive that bonds the
layers of PMMA together. This requires a great deal of pressure which is provided
by a Hot Roll Laminator, or similar device. After each layer is added to the growing
Lab-on-a-Disc platform and aligned, it is pressed gently to hold it in place and is
Fig. 5.19 Examples of the four DXF files corresponding to the four layers of PMMA
Fig. 5.20 Apparatus
required for disk assembly
5 The Centrifugal Microfluidic: Lab-on-a-Disc Platform 137