Mühendislik Fakültesi

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Citation Count: Eıldırım, E., Arıkan, M.A.S., Külah, H. (2012). A normally closed electrostatic parylene microvalve for micro total analysis systems. Sensors And Actuators A-Physical, 181, 81-86. http://dx.doi.org/10.1016/j.sna.2012.05.008
A normally closed electrostatic parylene microvalve for micro total analysis systems
(Elsevier Science SA, 2012) Yıldırım, Ender; Arıkan, M. A. Sahir; Kulah, Haluk; 120121
This paper presents an electrostatically actuated, normally closed microvalve for parylene microfluidics. The proposed valve structure isolates the fluid from the electric field, and hence results in relatively low actuation potentials (<60 V) irrespective of the working fluid. Hereby, the microvalve solves electrolysis or electrode shielding problems observed in electrostatic actuation in micro total analysis systems. To investigate leakage properties, microvalves were tested under pressurized flow with de-ionized (DI) water. No detectable leakage ratio was observed up to 20 kPa inlet pressure, due to the unique semicircular valve seat design. It was shown that the valve seat could be reconfigured to enable sealing at various pressure levels for different applications.
Citation Count: Yıldırım, E., Külah, H. (2011). Analysis and characterization of an electrostatically actuated in-plane parylene microvalve. Journal of Micromechanics and Microengineering, 21(10). http://dx.doi.org/10.1088/0960-1317/21/10/105009
Analysis and characterization of an electrostatically actuated in-plane parylene microvalve
(IOP Publishing LTD, 2011) Yıldırım, Ender; Kulah, Haluk; 31835; 120121
This paper presents analysis and implementation of a simple electrostatic microvalve designed for use in parylene-based lab-on-a-chip devices. The microvalve utilizes an in-plane collapsing diaphragm. To investigate the pull-in behavior of the diaphragm and flow characteristics, a thorough analysis is carried out using the finite element method. Microvalves with different diaphragm radii are fabricated using surface micromachining techniques. Pull-in tests are carried out under the no-flow condition with air, oil and water as the working fluid. Test results show that the pull-in occurs around 20 V for 450 mu m radius diaphragms with oil and air. However, it is not possible to observe pull-in up to 100 V (both ac and dc) for the case of water as the working fluid, due to its relatively high dielectric constant and conductivity. The flow tests show that no leakage flow was observed up to 4 kPa inlet pressure under 85 V actuation potential. The leakage ratio becomes 17% at 10 kPa inlet pressure. It is observed that the leakage can be reduced controllably by increasing the actuation potential, enabling the precise control of the flow rate
Citation Count: Yıldırım, E., Külah, H. (2012). Electrostatic energy harvesting by droplet-based multi-phase microfluidics. Microfluidics And Nanofluidics, 13(1), 107-111. http://dx.doi.org/10.1007/s10404-012-0946-2
Electrostatic energy harvesting by droplet-based multi-phase microfluidics
(Springer Heidelberg, 2012) Yıldırım, Ender; Kulah, Haluk; 120121
This paper presents an energy scavenging technique, merging microfluidics with electrostatic energy harvesting. The method employs droplet-based microflow of two phases with different electrical permittivities, resulting in a capacitance change across the microchannel, to harvest electrical energy. The technique is implemented on 3 mm wide, 1 mm deep minichannels. It is shown that 0.4 nW can be harvested using a single electrode pair, with air and water as the two phases flowing at 1 ml/min. The generated power can be increased significantly by microscale implementation, where the number of electrodes can also be increased for further improvement

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