Browsing by Author "Kulah, H."

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Citation - WoS: 12
Analysis and Characterization of an Electrostatically Actuated In-Plane Parylene Microvalve
(Iop Publishing Ltd, 2011) Kulah, H.; Yildirim, E.
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 - WoS: 3
Citation - Scopus: 8
An Electromagnetic Micro-Power Generator for Low Frequency Vibrations With Tunable Resonance
(Elsevier Science Bv, 2011) Turkyilmaz, S.; Zorlu, O.; Muhtaroglu, A.; Kulah, H.
This paper presents an electromagnetic (EM) micro-power generator with tunable resonance frequency which can harvest energy from low frequency environmental vibrations. The reported power generator up-converts low frequency environmental vibrations before mechanical-to-electrical energy conversion by utilizing two diaphragms with different resonance frequencies. Power is generated through electromagnetic induction by a magnet attached to the low frequency diaphragm, and a 50 turn, 2.1 Omega coil, and a magnetic piece on the high frequency diaphragm. Both of the diaphragms are fixed to a common frame via rubber springs, which makes the resonance frequency of each diaphragm tunable. The fabricated prototype generates 5.2 mV and 3.21 mu W RMS power by up-converting 13 Hz, 7.5 mm peak-to-peak vibrations to 200 Hz. Tunability of the resonance frequency is experimentally verified by operating the same device at 2-30 Hz external vibrations. (C) 2011 Published by Elsevier Ltd.
Citation - Scopus: 1
An Electrostatically Actuated Parylene Microvalve for Lab-On Applications
(2011) Kulah, H.; Arikan, M.A.S.; Yildirim, E.
This paper presents a novel electrostatic microvalve to control in-plane flow on parylene based lab-on-a-chip-devices. Normally-closed design of the microvalve insulates the working fluid from the electric field, while providing low leakage up to 40 kPa inlet pressure. Prototypes are fabricated and tested for pull-in and flow characterization. Pull-in voltage is measured to be 150 V independent of the working fluid. No leakage is detected up to 20 kPa inlet pressure. © 2011 IEEE.