Biomedical Engineering Reference
In-Depth Information
Pipette
loading
(a)
Inlet
Outlet
(b)
(c)
Add sample
Load sample
(d)
(e)
Slip into contact
Slip
(f )
(g)
Mixed
FIGURE 3.52
The.SlipChip..Scale.bars.for.(b),.(d),.and.(f).are.500.μm.and.for.(c),.(e),.and.(g) are.
250.μm..(From.Wenbin.Du,.Liang.Li,.Kevin.P..Nichols,.and.Rustem.F..Ismagilov,.“SlipChip,”.
Lab
Chip
.9,.2286-2292,.2009..Reproduced.with.permission.from.The.Royal.Society.of.Chemistry.)
SlipChip has already been successfully used for protein crystallization screening and digital
PCR.
3.8.2 Microluidic Resistors
Fluid low in microchannels, microvalves, and micropumps have many parallels with electrical
current through wires, switches, and current sources of microelectronic circuits. It is surprising
that the equivalent of a variable resistor, a very common electrical component, was not devel-
oped until fairly recently. In 2006, the author's laboratory presented “
microluidic resistors
,”
microchannel segments whose height can be constricted to increase low resistance (
Figure
3.53
). When the pneumatic lines are not pressurized (the microluidic resistor is “inactive”),
the top channels have a normal rectangular cross-section (
Figure 3.53a
). When the pneumatic
lines are pressurized, the membrane delects upward (the microluidic resistor is “activated”),
reducing the cross-sectional area of the microchannel to two narrow luid paths at the top cor-
ners (
Figure 3.53b
). he outputs of a three-inlet mixer (
Figure 3.53c-e
) can be predicted using
a purely resistive electrical circuit analogue.
