Browsing by Subject "Microvalve"

Now showing 1 - 3 of 3
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    Development of a MEMS Proportional Pneumatic Valve
    (2018-12) Hargus, Alex
    The MEMS proportional pneumatic valve employs an array of micro-orifices paired with piezobender micro-actuators in parallel to achieve macro-flow rates. This design produces a miniature valve that is extremely fast, lightweight, compact, and efficient. This thesis describes the design, fabrication, and testing of a MEMS valve prototype. The prototype was able to achieve a maximum flow of 0.107 slpm at 0 V and a minimum flow of 0.038 slpm at 30 V, making the turndown ratio about 2.8 at a pressure of 0.69 bar. Operation requires very little power, and the entire valve is about the size of a dime. These findings signify a step forward on the path to employing these valves in fluid power systems, especially mobile applications, but also reveal the potential of this technology to improve upon these results.
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    Fabrication and characterization of a polydimethylsiloxane microfluidic pump for direct-sampling neuroscience experiments, with in-line capillary electrophoresis - laser-induced fluorescence chemical analysis
    (2011-05) Graf, Neil J.
    A polydimethylsiloxane (PDMS) peristaltic micropump was designed, fabricated, and characterized, for intended use within rodent brain direct-sampling neuroscience experiments, with capillary electrophoresis - laser-induced fluorescence (CE-LIF) chemical analysis. The micropump was fabricated in-part using replica molding (REM) and injection molding. The micropump channel was formed by bonding an open PDMS Gaussianshaped micromolded channel, to a featureless slab of PDMS. Two pieces of capillary tube interconnects were sealed within the closed-off microchannel, and used to make connections with the outside world. The micropump was actuated using piezoelectric cantilevers, with a precision machined microvalve attached to the tip of each cantilever actuator. Registration of the cantilevers and microvalves over the PDMS microchannel, was accomplished with the aid of in-house machined micropositioners. The micropump was thoroughly characterized, for use and application as a bio-analytical add-on attachment device, to an already existing CE-LIF instrument. The micropump was characterized for: various microchannel geometries; different microvalve sizes, tilt, positioning, and shutoff performance; micropositioner design and performance; and, flow rate, backpressure, and peristaltic signal analysis. A P-Q (or H-Q) plot was formed, to represent the performance of the micropump for maximum attainable backpressure (P), versus flow rate (Q). The linear plot was formed by experimentally collecting fourteen individual data points, each corresponding to a unique micropump, “state.” The P-Q plot as discussed within Chapter VIII, is very potent, in providing a 5-for-1 benefit ratio. The P-Q plot allows an experimentalist to obtain: 1) a means to understand how the micropump output performance for both flow rate and backpressure, can be optimized for any particular microfluidic application, 2) an experimentally characterized micropump performance curve/s, 3) an experimentally characterized system curve, 4) the maximum power output of the micropump, and 5) a means to acquire a quantitative measure of the suction lift requirements associated with rodent brain direct-sampling neuroscience experiments. A control volume analysis is provided, to additionally articulate and facilitate discussion of the direct-sampling methodology. Preliminary pilot study direct-sampling data is also provided, as a means to justify and prove viability of the direct-sampling technique, for future characterization and optimization direct-sampling CE-LIF neuroscience studies.
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    Modeling, Fabrication and Testing of PZT Based MEMS and Meso-scale Pneumatic Proportional Valves
    (2019-12) Fikru, Nebiyu
    This thesis presents new modeling and process techniques used for the design and fabrication of Micro-Electro-Mechanical Systems (MEMS) based proportional valves for pneumatics applications. The modeling approach is further applied to a similar but larger envelope valve, hence called meso-scale valve, used to demonstrate the concept of the MEMS valve. Since the meso-scale valve is entirely fabricated in the machine shop using conventional machining technology and off-the-shelf components, the fabrication technique presented in the thesis applies to the MEMS valve only. The modeling work consists of two main sections: actuator modeling and flow modeling. In the actuator modeling section, a closed-form deflection equation of a piezoelectric bimorph is derived. The model takes into account the effect of the adhesive and electrode layers. The deflection model is used in a comprehensive steady state force model of a piezoelectric bimorph. In the flow modeling section, flow through the meso-scale and MEMS valves is modeled as an axisymmetric frictional flow between parallel plates. Friction factor is allowed to vary as a function of the Reynolds number in a new piecewise function for different regimes of the flow. The new flow modeling technique can be used estimate flow through the valve based on the position of the valve actuator. Without fabrication considerations, the actuator and flow modeling techniques are used to show that target specifications of 2cm3 MEMS valve with 700 kPa maximum pressure differential and 25 slpm flow capacity can be met. The success of such new MEMS valves has a revolutionary potential to miniature valve technology. The modeling techniques are used to design the final MEMS valve that was fabricated in the clean-room. The MEMS valve is created in a unique method that involves three separate processes: port plate fabrication, actuator fabrication, and bonding. In the port plate fabrication, the orifice array is created on standard silicon substrates using dry etching techniques. High aspect ratio (up to 20) through holes are created on standard silicon wafers using the technique. The actuator fabrication is performed on a separate substrate with bulk micromachining being the general fabrication methodology. Unique etch techniques have been used to release the actuator array. In the bonding process, adhesive bonding is used to permanently bond the port plate and the plate carrying the actuator array. The testing section presents testing of the port plates and actuators separately before testing the valves as complete sets. The port plate test results have demonstrated that target pressure and flow specifications of the MEMS valve are met. The actuator array tests have also shown that functional actuator arrays with deflection values that are nearly 90% of the predicted deflection have been successfully fabricated. The mesoscale valve test has produced results with proportional relationship between voltage and actuator deflection for a good range of the applied voltage. Several of the MEMS valves tested suffered from electrical shorting while in the test stand. However, one of the valves has shown promising results where flow rate increases with increases in applied voltage were recorded.