Biology Reference
In-Depth Information
is ideal, a class 10000 cleanroom is suffi cient to properly fabri-
cate a microdevice with feature sizes in the order of a few
micrometers. A less clean environment would often result in
fabrication defects.
4. The current design uses 100 mm diameter standard type sili-
con wafers in particular. For the current application the dop-
ant and orientation are not an issue. The size of the silicon
wafer is highly dependent on the UV exposure system at hand.
Silicon is preferred because of the good adhesion between sili-
con and the SU-8 photoresist, but the process can be per-
formed on other substrates as well.
5. The current design of the microfl uidic network is based on an
inlet, a linear distribution chamber, two series of symmetrical
microchannels and test chambers (top and bottom), two out-
lets, and a drain outlet at the end of the distribution chamber.
Only straight-shaped microchannels are used in order to
impose an initial direction of growth on the pollen tubes and
to obtain a homogeneous fl uid fl ow among the microchannels
[ 11 ]. In the setup shown here, the sizes of structural features
are chosen to fi t the dimensions of Camellia japonica pollen
grains and tubes. However, the design can be easily adapted to
serve different applications. The test chamber, for example, can
be modifi ed to allow for the integration of microelectrodes.
Examples for designs can be downloaded from the Optical-Bio
Microsystems Laboratory website ( http://users.encs.concor-
dia.ca/~mpackir/index.html ) and from the Geitmann Lab
website ( see Publications at http://www.geitmannlab.org ) .
6. In order to predict the fl uid-fl ow behavior within the micro-
fl uidic network, and particularly the movement of pollen
grains along the streamlines, a 2D Finite Element Method
(FEM) fl uid analysis implementing the incompressible Navier-
Stokes and continuity equations was carried out using
COMSOL. A velocity of 0.02 m/s was selected as the bound-
ary condition at the inlet to refl ect typical medium injection by
syringe, and the outlets were set to atmospheric pressure.
Since the liquid medium used here consists mostly of water
[ 7 ], the density (
ρ
) and the dynamic viscosity (
μ
) are set to
10 3 kg/m 3 and 10 −3 Pa s, respectively.
7. Be careful to use simple curves. Lines and arcs alone can be
used to draw most designs. Keep the amount of vertices to a
minimum and do not overlap any. Make sure the design is
composed of closed curves; by defi nition, no single curve
should be open. Once the skeleton of the drawing is done,
shade every region as necessary. In the current design we use
a negative photoresist (SU-8) to fabricate the mold; hence,
those regions that are not to be permanent in the mold must
be dark ( see Fig. 1c ).
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