6.2 Cutting PSA
Sheets of pressure sensitive adhesive are cut using a Graphtec automated knife
cutter. This device is controlled by the programme “Robo Master-Pro™Vision
4.6.0” which accepts the previously attained DXF files (alternative hardware /
software can be used) (Fig.5.15).
6.3 Dissolvable Film Tabs
Dissolvable film tabs are used to restrict the flow of fluid from one microfluidic
structure to the next by sealing the channel and creating a counteracting pressure
which pushes back the liquid. These DF tabs can be wetted and dissolved by
increasing the spin rate of the disc until the liquid comes in contact with the DF,
this is known as the burst frequency (Fig.5.16 ).
Firstly, the tabs are designed in CAD software by patterning an array of inner
circles that are equally spaced from each other as shown in Fig.5.17. Next, a second
sketch created to define the outer edge of the tabs; this is drawn with the same pitch
as the inner edges.
Fig. 5.15 Graphtec
automated knife cutter
Fig. 5.16 Examples of the four DXF files corresponding to the four layers of PSA
5 The Centrifugal Microfluidic: Lab-on-a-Disc Platform 135