Application of micromixers - Micromixers Fundamentals Design and Fabrication - page 328

Pattekar and Kothare [38] implemented a methanol-reforming system in silicon with a conversion
ratio of 90%. Holladay et al. [39] developed an integrated methanol-reforming system made of
stainless steel. The system consists of two vaporizers, a heat exchanger, a catalytic combustor, and
a catalytic methanol reformer. Kwon et al. [40] developed a fuel cell system made of silicon and glass.
The system consists of a fuel reformer, a preferential oxidation reactor, and a fuel cell. The system was
able to produce a power density of 230 mW/cm 2 at 0.6 V, which is comparable to an operation with
pure hydrogen.
9.2 APPLICATIONS IN CHEMICAL AND BIOCHEMICAL ANALYSIS
9.2.1 Concentration measurement
Micromixers are widely used in chemical, biological, and medical analysis fields. Almost every
chemical assay requires mixing of reagents with a sample. The basic T-mixer was used in the work of
Kamholz et al. [41] for the measurement of analyte concentration in a continuous flow. The
concentration of a target analyte is measured with the fluorescence intensity of the region where the
analyte and a fluorescent indicator have interdiffused [41] . Using this concept, the measurement of an
analyte concentration can be carried out based on a continuous basis. This device is referred to as
a T-sensor. The concept of a T-sensor is depicted in Fig. 9.3 . Kamholz et al. [41] used the T-sensor for
measurement of the concentration human serum albumin (HSA) in a sample. The fluorescein is
Albumin blue 580 (AB580), which has high affinity for HSA but low affinity for other types of
proteins. AB580 has an excitation wavelength of 580 nm and emits photons with a wavelength of
606 nm. The stream containing AB580 has low native fluorescence. However, the fluorescent intensity
increases a few orders of magnitude when AB580 binds to HSA. In a T-sensor, the solution of interest,
such as HSA sample, and the binding fluorescein, such as AB580, are introduced at the inlet. If the two
FIGURE 9.3
T-sensor: (a) concept and (b) intensity distribution across the mixing channel.