Online proceedings - EDA Publishing Association

coupling rotation movement in the Y and X directions as shown
in the X, Y, and Z components in Fig. 5. The area on the back of
the cylinder also flows rotationally in the Z direction. Rotation
in the Y direction was also generated at the end of the sensing
field. The flow chart also reveals the chaotic flow effect that
was generated in the microenvironment at this stage
(a)
(c)
(d)
Fig. 4 Vortices when (a) hc =300 m (b) hc = 400 m (c) hc = 500 m (d) hc =
600 m
(a)
(b)
(b)
11-13
May, 2011, Aix-en-Provence, France
PDMS solidifies after evacuation and heating. PDMS can be
removed from the inserts. Additionally, the atmospheric
pressure plasma can modify the convection channel and the
PDMS surface of the substrate. The parameter 0.5 Torr, 29.6
Watt, and 15 min~20 min represents pressure, plasma
efficiency, and surface modification time. The microchannel
was then connected with the substrate after PDMS was used to
implement the surface modification procedure.
3.2.2 Fluorescence streamline
For this part of the study, we utilized fluorescent particles
to examine the actual streamline condition of the microfluidics.
The fluorescent particles used had a grain size of 10m,
filtering band was between 460 and 490 nm. An Olympus IX71
fluorescent microscope was used in a dark environment to
provide the optical band that excites the particles, allowing the
fluorescent particles to generate fluorescence automatically
after photo-excitation in a specific band. When the fluorescent
particles move with the streamline in the channel, the trajectory
of the fluorescent particles reveals the actual streamline
condition of the microfluidics. Fig. 6 (a) shows the
experimental results of the fluorescent streamline. The fluid in
the figure rotates in direction Y when entering the sensing field
from the left. This is due to the height difference between the
bottom face of the sensing field and the inlet. When the fluidics
passes the cylindrical structure, it reveals an identical result to
the estimation implemented by the finite element simulation
software Fig. 6(b). The flow rate difference causes the fluid to
rotate toward direction Z at the back of the cylindrical structure.
(c)
Fig. 5 Simulation result when flow rate is 0.614 μm/s(a)Vorticity, x component
(b)Vorticity, y component(c)Vorticity, z component(d)Streamline
3.2 Microenvironment design
After analysis simulation by finite element software, a 1
mm cylindrical structure was added to the microenvironment.
The height of the structure was 500 m while the rate of flow in
the inlet area was 1500 ml / hr . The simulation result showed that
the vortices were generated when the structure had a large
speed difference. This phenomenon creates more opportunities
for viruses to collide with the sensing field, enhancing the
efficiency of the virus attachment to the field. We also
discovered that a relationship might exist between the strength
distribution of curl at the back of the cylinder and the
fluorescence strength distribution of the attachment experiment.
We discuss this further in Section 5.
3.3 Fluorescence streamline experiment
3.3.1 Fabrication of microfluidics environment
Firstly, stainless steel or brass was processed by a CNC
milling machine to produce the inserts designed in the study.
After the processed metal inserts were cleaned, PDMS and
hardener were fully mixed in a ratio of 10:1, and then PDMS
was poured into the channel and substrate inserts respectively.
(d)
(a)
Fig. 6 Streamlines by(a)fluorescent particles (b)simulation
IV. FABRICATION OF RECOGNITION LAYERS
First, the substrate and the microfluidic channel were
fabricated by PDMS casting. A layer of Au film was deposited
on the substrate by sputtering. Then, 20 mM 11-MUA
(11-mercaptoundecanoic acid) solution was injected on the
sensor surface by the microfluidics system. This links the
11-MUA with gold films as self-assembled monolayers. EDC
and NHS solutions (molar ratio, 2:1) were then injected on the
sensor surface by the microfluidics system. In the final step,
TYMV particles with fluorescent particles (NCD4) in the
buffer were introduced over the sensor surface at a different
flow rate. In the meantime, the sensor surface was rinsed and
dried in FPLC (Fast Protein Liquid Chromatography) to avoid
nonspecific adhesion. A confocal microscope was then used to
monitor the sensor surface.
To avoid the low-quality MUA molecular layer from
affecting the adhesion effect of TYMV, the study adopted
NCD-4 fluorescent particles as the sample and carried out tests
on the MUA molecular layers. By adopting a cross-linker
mechanism, NCD-4 and MUA can respond and bond more
(b)
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