Biomedical Engineering Reference
In-Depth Information
optimize pattern design by trial and error. As an empirical rule of thumb, PDMS
microchannels (or walls) that have aspect ratios between 1:1 and 1:10 work well for
most applications.
6. Solvent-based solutions cause PDMS to swell; hence, PDMS microchannels will
detach if illed with solvents for extended periods of time.
7. For some applications in which surface purity is paramount, there is the concern
that, under certain conditions, small amounts of dimethylsiloxane monomer may
also remain on the areas where the PDMS has contacted the surface.
8. Fabrication of the microchannel is a very low-throughput process because it takes hours
to produce a single PDMS replica and peeling it of the master is not easily automated.
9. Introduction of the solutions into the microchannels and starting/stopping low is not
easy to automate either, which limits microluidic patterning to research applications.
Note that, in microluidic patterning applications in which the deposition of material is
directed by light, another degree of versatility is introduced by patterning the light as well.
Patrick Doyle's group at the Massachusetts Institute of Technology (MIT) originally developed
this modality, dubbed
stopped-low lithography
. An example is shown in
Figure 1.25
. he
Railed microfluidic
channel
a
a'
a
b
Rail
Fin
Rail
a
PDMS
channel
a'
Ultraviolet
Slide glass
Fabricated
microtrain
Fabricated
microtrain
Oligomer
stream flow
c
d
Microscope
objective lens
Fin
z
y
Digital
micromirror
device
100 µm
50 µm
Microtrain
body
x
Ultraviolet
e
f
g
150 µm
Ends
150 µm
Flow
Flow
Flow
150 µm
Ends
Ends
FIGURE 1.26
“Railed”.microluidic.channels.for.guided.self-assembly..(From.Chung,.S.E.,.W..Park,.
S..Shin,.S.A..Lee,.and.S..Kwon,.“Guided.and.luidic.self-assembly.of.microstructures.using.railed.
microluidic. channels,”.
Nat. Mater.
,. 7,. 581,. 2008.. Reprinted. with. permission. from. Macmillan.
Publishers.Ltd.)
