Page 239 - Microsensors, MEMS and Smart Devices - Gardner Varadhan and Awadelkarim

APPLICATIONS 219

Figure 7.61 Design of a microconcentrator chip

there is a growing demand for a microconcentrator with molecular filtering. The basic
design and a prototype of the microconcentrator chip are shown in Figure 7.61 (Ikuta
el al. 1999). The overall chip size is 8 x 6 x 8.5 mm 3 and it consists of a microreactor
chamber divided by an ultrafiltration membrane. The lower part (A) of the microchamber
is filled with a high-concentration solution. A photodiode at the bottom can detect changes
of colour or intensity for use in biochemical luminescence tests. The transparent nature
of the polymer structures is an advantage over silicon. The fabricated device was used
to verify the concentration of protein in a biochemical reaction. The firefly protein,
luciferase, was used because it emits visible light with a wavelength of 560 nm in a
redox reaction with beetle luciferin. Therefore, the concentration of luciferase can be
determined from the intensity of the luminescence. In the experiments, the reagents
of luciferase, luciferin, and so on were premixed to supply to the concentrator. The
luminescence was observed from the chamber (A) at the underside of the ultrafiltration