Development of a bio-fluidic device for optical measurement and sample pretreatment

Abstract

In recent years, many attempts have been made to miniaturize complex biochemical analytical process in lab-on-a-chip. Both limit in analytical range and poor accuracy of data have originated from the requirements of each reaction and measurement step. For example, samples with high concentration have been difficulty in measuring the actual concentration because of the narrow measurable range of an analytical instrument. In case of spectrophotometers, they should be used in the region of absorbance 0.4~0.7, because the high absorbance value exceeds the upper boundary of the measurable range. This thesis has intended to develop a bio-fluidic device, which enable adaptive pretreatment of sample to fulfill an optimal condition of analysis. Using bio-fluidic technique, it would take an advantage that instrument itself responds spontaneously to change the sample with broad range of conditions. Like the automatic gain control of electrical devices, suitable fluidic actuation in sample pretreatment would make improvements, such as expanded domain of acquirable signal and enhanced precision. In this study, we have developed a bio-fluidic device for optical measurement and sample pretreatment, by an automatic dilution, or a typical pretreatment, which has been required for measurement. To embody automatic dilution, two idea was exploited; dilution with programmable ratio, and to-and-fro mixing. The bio-fluidic device was fabricated in replica molding using PDMS (polydimethylsiloxane). The experimental apparatus consisted of fluid actuating syringe pumps, spectrometer, and personal computer where a VC++ user control program run. To verify the automatic dilution by bio-fluidic device, red dye solution was used to demonstrate the to-and-fro mixing. In addition, the specific dilution process to reach the target concentration was accomplished. Full mixing required at least 15 times to-and-fros in case of the viscosity 2.095 cp. Finally, the bio-fluidic device was used to me...