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Development of a passive micro-ball valveWangwatcharakul, Worawut 19 October 2001 (has links)
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
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Comparison of two microvalve designs fabricated in mild steel using microprojection welding and capacitive dissociationTerhaar, Tyson J. 11 September 1998 (has links)
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
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Optimal control of a valve to avoid column separation and minimize waterhammer pressures in a pipelinePasha, Faiq Hussain, 1959- January 1989 (has links)
No description available.
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Development, testing, and evaluation of the central-flow, double- leaflet heart valveHerbert, James Dale January 1975 (has links)
M.S.
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An Electromagnetic Actuated Microvalve Fabricated on a Single WaferSutanto Bintoro, Jemmy 23 November 2004 (has links)
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.
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