Biomedical Engineering Reference
In-Depth Information
a
b
10
50
150
100
250
Bessel function distribution
8
200
300
400
350
450
Fiber default position
550
500
600
700
800
900
650
750
6
850
L
r
950
d
1000
1100
1200
1300
1400
1500 µL/min
d'
4
1050
1150
2
Bent fiber cantilever
1250
1350
0
Water @ wavelength of 1550 nm
1450
0
10000
20000 30000
Time (seconds)
40000
50000
60000
FIGURE 3.27
Measuring.low.rate.with.a.bending.iber..(From.V..Lien.and.F..Vollmer,.“Microluidic.
low.rate.detection.based.on.integrated.optical.iber.cantilever,”.
Lab Chip
.7,.1352-1356,.2007..
Reproduced.with.permission.from.The.Royal.Society.of.Chemistry.)
Ground electrode
Top plate
Glass substrate
Fluid layer
Hydrophobization
Droplet
Insulation
Glass substrate
Bottom plate
Control electrodes
FIGURE 3.28
Common.setup.for.manipulation.of.droplets.by.electrowetting..(From.H..Ren,.R..B..
Fair,. and. M.. G.. Pollack,. “Automated. on-chip. droplet. dispensing. with. volume. control. by. electro-
wetting.actuation.and.capacitance.metering,”.
Sens Actuators B Chem
.98,.319-327,.2004..Figure.
contributed.by.Richard.Fair.)
channels. Other platforms exist (for example, magnetic droplets can be moved around with
magnets) but do not have the versatility of these three, so we will not cover them here.
3.7.1 Electrowetting Platform: “Digital Microluidics”
In the electrowetting platform, the droplets are surrounded by air or oil and requires a layout
of electrodes in a parallel-plate glass chamber (
Figure 3.28
). Pioneering research on electrowet-
ting by Richard Fair and colleagues at Duke University, and many others, has demonstrated the
use of electrowetting to manipulate droplets with automation, a concept now dubbed
digital
microluidics
(see
Figure 3.28
). It is now possible to produce chips that generate small drop-
lets from large reservoirs and take them along paths deined by electrodes to mixing points
