Biomedical Engineering Reference
In-Depth Information
Input
valve
Output
valve
Diaphragm
valve
Flow
Pneumatic actuation
FIGURE 3.63
Peristaltic.micropumps.constructed.with.“doormat”.PDMS.microvalves..(From.W. H..
Grover,.A..M..Skelley,.C..N..Liu,.E..T..Lagally,.and.R..A..Mathies,.“Monolithic.membrane.valves.
and.diaphragm.pumps.for.practical.large-scale.integration.into.glass.microluidic.devices,”.
Sens.
Actuators B Chem.
.89,.315-323,.2003..Figure.contributed.by.Rich.Mathies.)
Liquid channel
Dynamic valve
region
Actuator
Pneumatic
supply channel
500 µm
FIGURE 3.64
PDMS.peristaltic.micropump.featuring.circularly.symmetric.microvalves..(From.O. C..
Jeong. and. S.. Konishi,. “Fabrication. of. a. peristaltic. micro. pump. with. novel. cascaded. actuators,”.
J. Micromech. Microeng.
. 18,. 025022,. 2008.. Reproduced. with. permission. from. the. Institute. of.
Physics.)
zero backpressure), likely because of the large size of the actuators (indeed, the maximum low
rate was observed at a very low frequency; ~2 Hz).
Regardless of the microvalve design of choice, peristalsis is typically actuated by the pattern
101, 100, 110, 010, 011, 001, in which 0 and 1 indicate open valves and closed valves, respectively.
Note that this operation, although suicient for many applications, requires three pneumatic
control channels, which consumes a lot of real estate on the chip and puts heavy constraints on
chip layout design.
3.8.4.4 “Single-Stroke” PDMS Peristaltic Micropumps
It was proposed early on by several groups that it should be possible to produce a peristaltic
motion using a single pneumatic channel that crosses the luidic channel several times in a
serpentine path: the time-delay introduced by the pressure wave traveling down the serpen-
tine channel is used as a substitute of the traditional time sequence used to produce peristalsis
(
Figure 3.65
). We stress that, although this design uses the same number of valves as the Quake
or the Mathies designs shown previously that featured one control line per valve, here, all three
valves are activated (at diferent times) with a single stroke. he concept was irst published in
2006 by Gwo-Bin Lee's group from National Cheng Kung University in Taiwan, who reported
large pumping rates (124 nL/s using a seven-membrane device operated at 9 Hz). his group
studied the delay lines and modeled them as electrical circuits containing resistors and capaci-
tors. On irst approximation, one could be tempted to model the transmission of the pressure
wave inside the pneumatic channel as sound through a rigid pipe, traveling at 343 m/s for dry air
