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