Analytical Chemistry Chemical Cytometry Quantitates Superoxide

Figure 6. Enzyme analysis that accompanies the manipulation of
three plugs. (A) Layout of the controlling flow channels (dashed line,
shaded) and flow channels for transport (solid line). For purposes of
clarity, the two flow channel networks are drawn separately in the
lower figure. (B) Fluorescence images showing the movement of the
H2O2 solution in the network of controlling flow channels (dashed
arrows) and solution plugs in the network of upper flow channels (solid
arrows). (1) The first solution was transported to the reaction chamber.
(2) After flushing of the first solution, the reaction chamber was
washed with the second plug. (3) After flushing of the solution, the
third solution was transported to the reaction chamber. Although the
flows in the controlling flow channels are described separately, they
began to flow in the flow channels simultaneously. The concentration
of the H2O2 solution injected into the controlling flow channel was
3.2 M. The dimensions of the chip were 33 mm × 27 mm.
6876 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010
Figure 7. On-chip detection of glucose and lactate using the device
shown in Figure 6. Dependence of the fluorescence intensity on the
concentration of glucose (O, 0) and lactate (b, 9). O and b indicate
data obtained in experiments using solutions that contained only
glucose or lactate. Five runs were performed, and the averages and
standard deviations are shown. 0 and 9 indicate data obtained by
filling the injection ports of pumps A and C with solutions containing
both glucose and lactate. The inset shows the plot at a lower
concentration range near the detection limits. The dashed lines show
the average +3σ of the background fluorescence.
of pressure that enables it to pass through a hydrophobic valve
set at the entrance.
CONCLUSIONS
Chemically actuated micropumps can be realized by making
use of the volume change produced by the catalytic decomposition
of H2O2. The pumps are located along a controlling flow channel
that transports a H2O2 solution via capillary action. The row of
pumps can be switched on sequentially following the introduction
of the H2O2 solution into the controlling flow channel. The
structure of the pump itself can also be used to exert pressure
upon a solution in a flow channel. The timing of the switching
among pumps can be adjusted by locating them at appropriate
positions in a network of flow channels or by employing
additional structures such as compartments and/or constrictions.
In other words, the information for switching among
pumps is directly described on the chip as a program.
As demonstrated, one potential application for our autonomous
devices is that of portable analysis systems. Although on-chip
biochemical analyses for molecules such as proteins have already
been carried out using integrated microfluidic components, 6,27,28
this technique will simplify the construction of the entire system.
Moreover, such an autonomous device can be useful for a variety
of purposes, such as micromixing, 23 tissue culturing, 19 and
gas-liquid reactions, 17 since it can minimize the burden involved
in the handling of solutions.
Received for review April 12, 2010. Accepted July 8, 2010.
AC1009657