Xiao, Peng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 76-78). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.iii / ACKNOWLEDGEMENTS --- p.iv / TABLE OF CONTENTS --- p.vi / LIST OF FIGURES --- p.viii / LIST OF TABLES --- p.xi / Chapter CHAPTER ONE --- INTRODUCTION --- p.1 / Chapter 1.1 --- The Thermal Characteristic of the CNT Heater --- p.1 / Chapter 1.2 --- CNT-Based Micro Bubble Generation in a Static Droplet of Water --- p.2 / Chapter 1.3 --- CNT-Based Micro Bubble Transportation in a Micro Channel --- p.4 / Chapter 1.4 --- CNT-Based Micro Bubble Stimulation by Pulsed Current --- p.4 / Chapter CHAPTER TWO --- THE THERMAL CHARACTERISTICS OF CARBON NANOTUBES --- p.6 / Chapter 2.1 --- Temperature Coefficient of Resistance (TCR) of Our Typical CNT Heater --- p.7 / Chapter 2.2 --- The Humidity Coefficient of the Resistance (HCR) for Our Typical CNT Heater --- p.13 / Chapter 2.3 --- The Conclusion of the CNT Heater's Thermal and Humidity Characteristics --- p.18 / Chapter CHAPTER THREE --- MICRO BUBBLE GENERATION WITH MICRO WATT POWER USING CARBON NANOTUBE HEATING ELEMENTS --- p.19 / Chapter 3.1 --- Micro Electrode Fabrication --- p.19 / Chapter 3.1.1 --- Methods for Metal Electrode Fabrication --- p.20 / Chapter 3.1.2 --- Advantages and Disadvantages of Two Micro Fabrication Methods --- p.22 / Chapter 3.1.3 --- The Fabrication of Micro Electrodes for Our CNT Heater --- p.24 / Chapter 3.1.4 --- The Mask Design for Metal Electrode Fabrication --- p.26 / Chapter 3.2 --- The Micro Bubble Generation Experimental Procedure --- p.28 / Chapter 3.2.1 --- Initial Analysis of the Experimental Device --- p.28 / Chapter 3.3 --- Theoretical Analysis of Bubble Generation Temperature on the CNT Heater --- p.31 / Chapter 3.3 --- The Analysis of the Micro Bubble Generation Experimental Results --- p.35 / Chapter 3.4 --- The Conclusion of Bubble Generation in a Static Droplet of Water --- p.44 / Chapter CHAPTER FOUR --- CARBON NANOTUBE-BASED MICRO BUBBLE GENERATION IN A MICRO CHANNEL WITH DYNAMIC FLUID --- p.45 / Chapter 4.1 --- Micro Channel Fabrication --- p.46 / Chapter 4.1.1 --- Rapid Prototyping --- p.46 / Chapter 4.1.2 --- PDMS Moulding --- p.47 / Chapter 4.1.3 --- Irreversible Sealing --- p.49 / Chapter 4.1.4 --- Mask Design --- p.50 / Chapter 4.2 --- Experimental Setup --- p.51 / Chapter 4.3 --- Experimental Procedure --- p.53 / Chapter 4.4 --- Experimental Results --- p.55 / Chapter 4.5 --- Conclusion for Bubble Generation in the Micro Channel with Dynamic Fluid --- p.59 / Chapter CHAPTER FIVE --- CNT-BASED MICRO BUBBLE STIMULATION BY PULSED CURRENT --- p.60 / Chapter 5.1 --- Attempt to Control the Micro Bubble Diameter --- p.61 / Chapter 5.2 --- The Pulsed Current for Micro Bubble Departure in the Micro Channel --- p.63 / Chapter 5.2.1 --- Manual Pulsed Current Stimulation for Micro Bubble Departure in the Micro Channel --- p.64 / Chapter 5.2.2 --- The Pulsed Current Circuit for Micro Bubble Departure in the Micro Channel --- p.67 / Chapter CHAPTER SIX --- FUTURE WORK AND SUMMARY --- p.70 / Chapter 6.1 --- Future Work for Micro Bubble Generation Projects --- p.70 / Chapter 6.1.1 --- The CNT-Based Micro Bubble Generation with Various Values of Input Current --- p.70 / Chapter 6.1.2 --- The CNT Heater in the Zig-Zag Micro Channel --- p.71 / Chapter 6.1.3 --- Summary --- p.72 / APPENDIX A --- p.73 / Fabrication Process --- p.73 / Chapter I. --- Micro Electrode Fabrication --- p.73 / Chapter II. --- Micro Channel Fabrication --- p.75 / BIBLIOGRAPHY --- p.76

Micromanufacturing consists of processes for producing structures, devices or systems with feature sizes measured in micrometers. Micromanufacturing began in the mid-1960's with microelectronics fabrication technology. In the 1980's, Micro-Electro-Mechanical Systems (MEMS) began to be developed, in which electrical and mechanical subsystems were integrated at small scales. More recently, Microtechnology-based Energy and Chemical Systems (MECS) have been developed that have led to improved heat and mass transfer in energy and chemical systems. At Oregon State University, new methods to fabricate MECS have been developed. One of the new methods involves microlamination--bonding thin strips of different materials together. This method has generated a high volume and low-cost approach to the production of high-aspect-ratio (height-to-width) structures. Past efforts to make microfloat valves using microlamination methods resulted in an 11:1 diodicity ratio. It was hypothesized that the valve had a ridge of redeposited material around the valve seat caused by the condensation and deposition of ablation ejecta during laser machining. The contribution of this thesis is the creation of a microfloat valve using an Electrochemical Micromachining (EMM) method. EMM methods are known to produce smooth surfaces, free of burrs or any other types of aspirates. Therefore, it was hypothesized that float valves made with EMM methods would improve valve performance. Four steps were involved in the creation of the microfloat valve: lamina formation, laminae registration, laminae bonding and component dissociation. A total of 9 laminae-some of which were made with 304 stainless steel 76.2 ��m thick, others of which were made with 50.8 ��m thick polyimide-made up the microfloat valve. Photolithography and EMM were used to form the lamina. Even though the laminae created by EMM were smaller in size than desired, the machined areas did not have redeposited material, and some areas had straight walls. In laminae registration, a two edge registration method was used. In the laminae bonding step, laminae were bonded by the adhesive method at 248��C under 135 kPa pressure for 13.5 minutes. In the component dissociation step, a capacitor dissociation method that was designed at OSU was used. Upon performance testing, the average diodicity ratio for the EMM valve was 12.45 over the range 0 kPa-450 kPa, indicating improved performance when compared to the Laser Ablation valve-which had an average 11.17 over the range 0 kPa-100 kPa. Microscope examination of valves revealed that statistically significant improvement in valve performance would require refinement of component dissociation methods. / Graduation date: 2000

Since the dawn of the computer age, there has been a push to create miniature devices. These devices were initially integrated circuit (IC) devices to perform calculations for computers. As the technology progressed, the scope of the devices diverged to included microelectromechanical (MEMS) devices, meaning that the devices perform mechanical movements via electrical actuation. More recently, a new generation of devices has evolved called microtechnology-based energy and chemical systems (MECS). MECS may employ MEMS technology, however the systems are not designed to produce only mechanical movement. MECS deal with heat and mass transfer, the basic processes used in energy, chemical and biological systems, in the mesoscale realm. Mesoscale devices range from the size of a sugar cube to the size of a human fist. The possibilities of MECS have not been realized. Heating and cooling systems, chemical mixing/distribution, and locking systems are all potential applications. The devices require: 1) revolutionary design, accounting for the scaling effects on device performance; 2) new fabrication technologies for the creation of these designs; and 3) good material properties for mechanical and chemical interactions. Fabrication requirements for MECS are different than for MEMS in that MECS generally require non-silicon metals. Metal microlamination (MML) has been introduced as a general practice for meeting the fabrication requirements for MECS. Prior MML fabrication methods have emphasized the use of diffusion bonding, soldering, or brazing techniques. This thesis will introduce: 1) a novel microflapper valve design fabricated in mild steel using a novel microprojection welding technique; 2) a novel microfloat valve design fabricated in mild steel using a novel capacitive dissociation process for creating free floating geometries. The devices are characterized by comparing actual flow rates to theoretical flow rates of equivalent orifice sizes. Preliminary results show that the microfloat valve achieved an average diodicity (free flow versus leakage rate) ratio of 11.19, while the microflapper valve achieved an average diodicity ratio of 4.08. The theoretical orifice sizes of the microfloat and microflapper valves are 0.629 mm and 0.611 mm respectively. These results suggest that the float valve is the superior design. / Graduation date: 1999

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 47-50).

Multilayer microwave circuit processing technology is essential in developing more compact radio frequency (RF) electronically scanned arrays (ESAs) for next generation radar systems. ESAs are typically realized using the hybrid connection of four discrete components: RF manifold, phase shifters or Butler matrices, antennas and T/R modules. The hybrid connection of these components increases the system size, packaging cost and introduces parasitic effects that lead to higher losses. In order to eliminate these drawbacks, there is a need to integrate these components on the same substrate, forming a monolithic phased array. RF MEMS technology enables the monolithic integration of the ESA components into one highly integrated multifunctional module, thereby enhancing ESA designs by significantly reducing size, fabrication cost and interconnection losses. A novel capacitive dual-warped beam shunt MEMS switch is presented that utilizes warped beams to enhance its RF performance. This switch exhibits an off-to-on capacitive ratio of almost 170, isolation better than 40dB, switching speeds as low as 6μs without the need for thin dielectrics or high dielectric constant materials. These MEMS switches are implemented into single pole three throw (SP3T) and single pole four throw (SP4T) configurations. A novel 3-bit finite ground coplanar waveguide switched delay line MEMS phase shifter is developed with four cascaded SP3T dual-warped beam capacitive switches to achieve low-loss performance and simplify ESA design. The fabricated prototype unit exhibits an insertion loss of 2.5∓0.2dB with a phase error of ∓6°. Moreover, a compact 4 x 4 Butler matrix switchable with the use of a MEMS SP4T switch is investigated as an alternative passive beamforming method. The overall beam-switching network is monolithically integrated within a real-estate area of 0.49cm2. This technique provides a unique approach to fabricate the entire beamforming network monolithically. An 8-mask fabrication process is developed that monolithically integrates the MEMS phase shifter and RF combining network on one substrate. The wafer-scale integrated ESA prototype unit has an area of 2.2cm2. It serves as the basic building block to construct larger scanning array modules and introduces a new level of functionality previously achieved only by the use of larger, heavier and expensive systems

Due to the potential uses and advantages of 3D microelectromechanical systems (MEMS), research has been ongoing to advance the field. The intention of my reasearch is to explore different gripper designs and their interaction with corresponding components to establish a 3D microassembly system. In order to meet these goals, two grippers were designed using different mechanisms for grasping. At the same time, corresponding parts capable of being constructed into a 3D microstructure were designed to interact with the grippers. The microcomponents were fabricated using PolyMUMPS, a part of the Multi-User MEMS Processes (MUMPS), and experimentation was conducted with the goal of constructing a 3D microstructure. The results were partially successful in that both grippers were able to pick up corresonponding parts and bring them out of plane in order to make them stand up. However, a final 3D microstructure was unfortunately not achieved due to time constraints. This will be left to future researchers who continue the project. On the equpiment side a microassembly system was fully integrated using cameras for vision and motors with micro-resolution for movement. A computer program was used to control each part of the system. The cameras provided feedback from various views, allowing the operator to observe what was happening to the microcomponents. The grippers were attached to one of the motors and manipulated to pick up the parts. The final overall system proved sufficient for microassembly, but had some areas that could be improved upon.

Multilayer microwave circuit processing technology is essential in developing more compact radio frequency (RF) electronically scanned arrays (ESAs) for next generation radar systems. ESAs are typically realized using the hybrid connection of four discrete components: RF manifold, phase shifters or Butler matrices, antennas and T/R modules. The hybrid connection of these components increases the system size, packaging cost and introduces parasitic effects that lead to higher losses. In order to eliminate these drawbacks, there is a need to integrate these components on the same substrate, forming a monolithic phased array. RF MEMS technology enables the monolithic integration of the ESA components into one highly integrated multifunctional module, thereby enhancing ESA designs by significantly reducing size, fabrication cost and interconnection losses. A novel capacitive dual-warped beam shunt MEMS switch is presented that utilizes warped beams to enhance its RF performance. This switch exhibits an off-to-on capacitive ratio of almost 170, isolation better than 40dB, switching speeds as low as 6μs without the need for thin dielectrics or high dielectric constant materials. These MEMS switches are implemented into single pole three throw (SP3T) and single pole four throw (SP4T) configurations. A novel 3-bit finite ground coplanar waveguide switched delay line MEMS phase shifter is developed with four cascaded SP3T dual-warped beam capacitive switches to achieve low-loss performance and simplify ESA design. The fabricated prototype unit exhibits an insertion loss of 2.5∓0.2dB with a phase error of ∓6°. Moreover, a compact 4 x 4 Butler matrix switchable with the use of a MEMS SP4T switch is investigated as an alternative passive beamforming method. The overall beam-switching network is monolithically integrated within a real-estate area of 0.49cm2. This technique provides a unique approach to fabricate the entire beamforming network monolithically. An 8-mask fabrication process is developed that monolithically integrates the MEMS phase shifter and RF combining network on one substrate. The wafer-scale integrated ESA prototype unit has an area of 2.2cm2. It serves as the basic building block to construct larger scanning array modules and introduces a new level of functionality previously achieved only by the use of larger, heavier and expensive systems

Due to the potential uses and advantages of 3D microelectromechanical systems (MEMS), research has been ongoing to advance the field. The intention of my reasearch is to explore different gripper designs and their interaction with corresponding components to establish a 3D microassembly system. In order to meet these goals, two grippers were designed using different mechanisms for grasping. At the same time, corresponding parts capable of being constructed into a 3D microstructure were designed to interact with the grippers. The microcomponents were fabricated using PolyMUMPS, a part of the Multi-User MEMS Processes (MUMPS), and experimentation was conducted with the goal of constructing a 3D microstructure. The results were partially successful in that both grippers were able to pick up corresonponding parts and bring them out of plane in order to make them stand up. However, a final 3D microstructure was unfortunately not achieved due to time constraints. This will be left to future researchers who continue the project. On the equpiment side a microassembly system was fully integrated using cameras for vision and motors with micro-resolution for movement. A computer program was used to control each part of the system. The cameras provided feedback from various views, allowing the operator to observe what was happening to the microcomponents. The grippers were attached to one of the motors and manipulated to pick up the parts. The final overall system proved sufficient for microassembly, but had some areas that could be improved upon.

No description available.