Power-free microfluidic actuator based on indirect pressurization for biological sample preparation and analysis

Abstract

Microfluidic technologies have a number of advantages for sample preparation and analysis in point-of-care testing (POCT), but the needs of external pumping systems limit the wide use of them. To eliminate the needs of complicated external pumping systems, various power-free microfluidic devices have been developed. However, it is still challenging for on-demand control of various flow mechanisms without the use of any external equipment. In this thesis, I present a finger-actuated microfluidic device based on indirect pressurization to control a set amount of fluid regardless of differences in end users. Using a diaphragm, active and passive check valve, not only dispensing, but also reciprocation, flow direction control, and mixing of multiple reagents was demonstrated and each flow behavior was characterized. By applying the proposed flow mechanisms, I developed the devices for practical microfluidic sample preparation and analysis in POCT. First, the devices for blood typing and cross-matching test was developed as pre-transfusion tests to prevent hemolytic transfusion reaction. As rapid pre-transfusion tests for urgent transfusion patients, the results can be simply obtained by pushing the button. A smart blood typing system was introduced that displays the letters of blood type as a first-line test, and a fully-integrated cross-matching test was demonstrated as a final verification. Second, conventional solid-phase nucleic acid purification procedure was simplified using the finger-actuated microfluidic devices. The reagents are sequentially delivered to the silica bead column via a predesigned fluidic path according to the actuated button to obtain purified nucleic acid. A reciprocating flow was further assisted to enhance the recovery rate of nucleic acid. As a target analyte, standard Hepatitis B virus (HBV) DNA was successfully purified with up to 50% of the recovery rate. Third, the proposed device was conducted to substitute accurate manual pipetting or robotic arms required for conventional biological analysis. As a potential application, a finger-actuated microfluidic concentration gradient generator was developed for studying enzyme kinetics, and the device was utilized for spheroids culture and analysis in hanging drop array. In addition to applications presented in this thesis, the proposed device can be widely used as a robust tool to facilitate sample preparation and analysis in POCT, and conventional biological analysis.