|dc.description.abstract||Traditionally, controllers are an integrated electronic circuit (IEC), which is composed of basic modules such as diodes and transistors to provide various logic functions, e.g., switching. The so-called hard material refers to materials that have high Young’s moduli in comparison with Young’s moduli of animal body; otherwise soft material is called. The controller built from IEC is called hard controller or controller in this thesis. To build a circuit with soft materials, the fluid is naturally taken as a substance, and a circuit can be made by integrating fluid flow and micro-channel deformation. Such a circuit is called integrated micro-fluidic circuit (IMC). The controller built from IMC is called soft controller.
This thesis was devoted to study IMC, particularly taking the switching valve as a study vehicle. It is noted that the switching valve in IMC corresponds to the diode in IEC. The specific objectives of this thesis are: (1) to develop a new architecture of IMC such that the number of layers of IMC can be reduced to one only, and (2) to build a prototype of the IMC switching valve to explore the feasibility of fabrication of the switch valve based on the proposed architecture in (1).
A comprehensive literature study has resulted in the proposed architecture, which is to “turn” a vertically stacking structure into a horizontally stacking structure. As such, the fluid in the micro-channel horizontally presses the thin wall (or membrane) of the micro-channel to close the micro-channel completely (i.e., the flow is off). Design of a particular switch valve with the help of the axiomatic design theory was carried out. Simulation of the design was carried out by using the multi-physics software COMSOL, which confirmed that if the width of the micro-channel is 13 μm, the membrane with the thickness of 5 μm (length of 140 μm; width of 10 μm) can deflect more than 13 μm, thus closing the micro-channel completely.
The design was then fabricated on the Micro-fabrication facility at Canadian Light Source. Specifically, the material for the switching valve is PDMS owing to its suitable Young’s moduli and excellent biocompatibility and the UV lithography together with soft lithography was employed to fabricate the device. Given the capability of the fabrication facility, the membrane with the thickness of 50 microns in the micro-channel was possibly made, which is unfortunate. Due to this reason, a preliminary experiment was performed to observe the deflection of the membrane only, and the result confirmed the expected deflection qualitatively. This limited experiment however helped to verify the simulation system, which thus ensures a certain degree of reliability of the result given by the simulation, namely the complete closure of the channel by the membrane which has the thickness of 5 μm, length of 140 μm, and width of 10 μm. A side finding from this study is that a switching action may not result in 0 (off) or 1 (on) only but x% and y%, where x and y are flow rates and x%+y%=100%. This thesis names such a switch valve continuous switch valve.
The main contributions of the thesis lie in the field of micro-fluidics, and they are: (1) the provision of the proposed architecture of IMC which has one layer in the vertical direction, and (2) the provision of the new concept of switching, namely the continuous switching. The continuous switching may have further implication to information processing, as it departs away from the 0-1 approach, and to actuation, as it exhibits an analogous property as opposed to a digital property.||
|dc.subject||MEMS, Microfluidic, Switch valve, embedded instruction, deformation, membrane, micro fluid, INTEGRATED CONTINUOUS MICRO-FLUIDIC||