A novel design, material, and fabrication method are presented to fabricate a passive micro-ball valve. Microvalves are critical components in microflow control devices used to control the fluid flows in microchannels. These microflow control devices can be integrated with microsensors to form micro analysis systems. Glass/silicon-based fabrication is complicated and expensive. Therefore, other materials and fabrication methods have been proposed. In this research, Melinex 453, a polyester film, and pressure sensitive adhesives were used to fabricate a micro-ball valve by a microlamination method. The valve was designed to have a 450 μm diameter glass ball floating inside a chamber size of 800 μm. The ball will permit flow in the forward direction and impede flow in the reverse direction. The fabrication method consists of three steps: patterning, registration and bonding. The patterning step was accomplished using laser micromachining. Registration and bonding were performed with the use of a pin-alignment fixture. Pressure sensitive adhesive was used in the bonding step using double-sided acrylic adhesive tape. The micro-ball valve has advantages over other microvalves in terms of little dead volume, simple design, disposability, low operating pressure in forward direction, and low leakage in reverse direction. The micro-bal1 valve was characterized by pressure drop testing at different flow rates from 1 to 7.5 ml/min. The experimental results tend to agree with a simple theoretical model of the pressure drop through an orifice. Moreover, an average pressure drop diodicity of at least 2980 has been achieved. / Graduation date: 2002

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

No description available.

A review of the literature revealed that 1) all prosthetic heart valves to date are plagued by certain problems, 2) all prosthetic valves in current clinical use are central-occlusion valves which do not effectively simulate natural valve action, and 3) the development of a true central-flow valve with the potential benefits of reduced pressure drop, turbulence, hemolysis, and thromboembolism could be a significant contribution. A central-flow, double-leaflet valve was developed. The wear, pressure drop, turbulence, and regurgitation associated with the new valve were evaluated. The wear test results indicated the need for additional testing using more wear resistant pin-bearing combinations. The flow tests revealed that the new valve with a 65 degree opening angle produced less pressure drop than other prostheses, but the new valve did not reduce turbulence as compared to other prostheses. In addition, the backflow and mean leak associated with the new valve were too high. Details of the testing procedures are presented and recommendations for future valve modifications and testing are included. / M.S.

Microvalves are essential components of the miniaturization of the fluidic systems to control of fluid flow in a variety of applications as diverse as chemical analysis systems, micro-fuel cells, and integrated fluidic channel arrangements for electronic cooling. Using microvalves, these systems offer important advantages: they can operate using small sample volumes and provide rapid response time. This PhD dissertation presents the world first electromagnetically actuated microvalve fabricated on a single wafer with CMOS compatibility. In this dissertation, the design, fabrication, and testing results of two different types of electromagnetic microvalves are presented: the on/off microvalve and the bistable microvalve with latching mechanism. The microvalves operate with power consumption of less than 1.5 W and can control the volume flow rate of DI water, or a 50% diluted methanol solution in the range 1 - 50 µL in. The leaking rate of the on/off microvalve is the order of 30 nL/min. The microvalve demonstrated a response time for latching of 10 ms in water and 0.2 ms in air. This work has resulted in a US patent, application no. 10/699,210.Other inventions that have been developed as a result of this research are bidirectional, and bistable-bidirectional microactuators with latching mechanism, that can be utilized for optical switch, RF relay, micro mirror, nano indenter, or nano printings.