Development of an Indirect-heating Thermo-pneumatic Micropump and a Microfluidic Platform with Application Demonstration

In this work, the development of an indirect-heating thermo-pneumatic micropump and a microfluidic platform integrated with indirect-heating thermo-pneumatic valves (IH-TPVs) are presented. The proposed indirect-heating thermo-pneumatic mechanism possesses the advantages of simple device structure, simple actuation scheme, relatively low actuation voltage, and small system size, while temperature elevation on working fluid caused by thermo-pneumatic actuation can be significantly reduced. The indirect-heating thermo-pneumatic valves integrated in a microfluidic platform serve as the interfaces between reaction zones for sequential laboratorial operations. Also, DNA sample preparation and amplification are demonstrated using the microfluidic platform.

The indirect-heating thermo-pneumatic mechanism consists of two separate zones for air-heating and fluid-squeezing. Temperature elevation on working fluid can be significantly reduced since the fluidic channel surface is away from the actuation heater. Furthermore, the flow rate performance of the indirect-heating micropump can be improved by increasing the applied voltage, while relatively low temperature elevation on working fluid is induced.

Based on the proposed actuation scheme, indirect-heating thermo-pneumatic valves are designed and integrated into a microfluidic platform, which is capable of carrying out a series of laboratorial operations on a disposable chip. The platform employs coil arrays to transport biological samples attached on magnetic beads through different reaction zones in aqueous solutions. Indirect-heating thermo-pneumatic valves are adopted as the interfaces between sequential reactions. The self-contained system is composed of a disposable microfluidic reaction (MFR) chip and a fluidic driving/sensing (FDS) module. On the MFR chip, various reaction zones with different functionalities are implemented. Also, indirect-heating thermo-pneumatic valves, which are monolithically integrated into the disposable MFR chip, are proposed for interfacing adjacent reaction zones. On the FDS module, arrays of coils are implemented for electromagnetically transporting sample-carried magnetic beads through different reaction zones in aqueous solutions. In addition, micromachined chips with heating and sensing capabilities are integrated on the FDS module for actuating the valves and controlling the temperature of the reaction zones. A series of laboratorial operations, including DNA extraction, purification and amplification (polymerase chain reaction, PCR), is performed by using the proposed microfluidic system. Since the driving circuits for the coil arrays, the thermally-driven valves, and the heaters are very simple, the proposed system is self-contained and can be fully operated with a simple DC power supply.