Biomedical Engineering Reference
In-Depth Information
a
∆P
Q
0
Q
0
Q'<Q
0
b
∆P
Q'
Q'
A
B
C
A
B
C
A
B
C
c
d
e
n
A
:
n
B
:
n
C
1:6:14
n
A
:
n
B
:
n
C
14:1:6
n
A
:
n
B
:
n
C
6:14:1
FIGURE 3.53
Microluidic. resistors. using. inlatable. elements.. (From. Eric. W.. Lam,. Gregory. A..
Cooksey,.Bruce.A..Finlayson,.and.Albert.Folch,.“Microluidic.circuits.with.tunable.low.resistances,”.
Appl. Phys. Lett.
.89,.164105,.2006..Figure.contributed.by.Eric.Lam.)
A limitation of the design of the microluidic resistors in
Figure 3.53
is that they need to
be calibrated because it is not possible to accurately predict the low resistance of the channel
with delected membranes (the uncertainties in both the delected geometries and in the PDMS
Young's modulus are too large). A more predictable design uses microvalves to divert low (or
not) through highly resistive channels (
Figure 3.54
). Depending on the number of side channels
that are open, the circuit becomes more or less resistive; because all the channels are made with
rectangular cross-sections, the low resistances can be predicted with straightforward formulas
(see
Equation 3.12
).
2 mm
350 µm
(a)
(b)
(c)
R
0
V
R1
R
1
R
v
V
R2
R
2
≈ 2.0 × R
1
V
R3
(d)
(e)
R
3
≈ 4.2 × R
1
V
R4
R
4
≈ 7.6 × R
1
{0000}
FIGURE 3.54
Microluidic.resistors.using.microvalves..(From.Gregory.A..Cooksey,.Christopher.G..
Sip,.and.Albert.Folch,.“A.multi-purpose.microluidic.perfusion.system.with.combinatorial.choice.of.
inputs,.mixtures,.gradient.patterns,.and.low.rates,”.
Lab Chip
.9,.417-426,.2009..Reproduced.with.
permission.from.The.Royal.Society.of.Chemistry.)
