A STUDY OF A CONTINUOUS INTEGRATED MICROFLUIDIC CIRCUIT SWITCH VALVE

Abstract

The need of making microfluidic devices less bulky and being independent of external controls (or self-controls) has inspired the development of the device concept called Integrated Microfluidic Circuits (IMCs). The IMC concept is similar to the concept of embedded instruction in electronic circuits. So, an IMC device has a self-control ability, and this ability is gained with the solid film or membrane being incorporated into the micro-channels or chambers. The focus of this thesis is on the IMC based switch valve that can perform a continuous flow switching function. The difference between a discrete flow and a continuous flow is that in the former, the switching function is upon either Flow A or Flow B, while in the latter, the switching function is upon either the flow configuration (Flow A with the flow rate x & Flow B with the flow rate y) or the flow configuration (Flow A with the flow rate y & Flow B with the flow rate x), where x + y = constant. The concept of the continuous IMC switch valve was initially speculated in a MS thesis in our research group.

The overall objective of the present thesis was to explore the feasibility of the continuous IMC-based or IMC switch valve. Two specific objectives were defined in the thesis to achieve the overall objective, namely (1) to design and fabricate a device that is composed of IMC switch valves so that feasibility of the concept of continuous flow switching can be studied, and (2) to develop a simulation test-bed as well as a preliminary physical test-bed so as to comprehensively examine the switching behavior of the device developed in (1).

The device was designed by employing the axiomatic design theory and the general design phase theory in order that the design process for the continuous IMC switch valve has some generalized implication to other types of IMC devices. The device was fabricated with the 3D Printed Transfer Molding (PTM) technology due to its simplicity as opposed to the conventional soft lithography technology. In particular, the material for the device is Polydimethylsiloxane (PDMS), and material for the mold is Full cure835 Vero white plus. Further, process parameters were tailored based on a trial-and-error procedure. The testing of the integrity of the fabricated device, leakage test in particular, was conducted. The simulation system was built with the software COMSOL, which is for multi-physics modeling and simulation and is therefore suitable to this thesis. These research activities along with the results can draw the following conclusions: (1) the design process for the continuous IMC switch valve has some generalized implication to other types of IMC devices; (2) the fabricated device is free of leakage; (3) the chosen mold material along with the specific fabrication protocol is effective to PDMS micro-parts and devices; (4) the continuous IMC-based or IMC switching function is feasible based on the simulation result on the device as developed in this thesis.

The contributions of this thesis in the field of the microfluidic device technology are: (1) a proof to the device concept of the continuous IMC switch valve, (2) a systematic design process for both discrete and continuous IMC switch valves as well as possible other types of IMC devices, and (3) a proprietary PTM process to fabricate PDMS micro-parts.