Browsing by Author "Leblebici, Y."

Now showing 1 - 3 of 3

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Cantilever array oscillators with nonlinear optical readout
(IEEE, 2015) Lüleç, S. Z.; Adiyan, U.; Yaralıoğlu, Göksen Göksenin; Leblebici, Y.; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
MEMS array oscillators typically require a separate detector and feedback loop for each oscillator. We show that grating-based-optical-readout induces nonlinearity, which enables simultaneous operation of an array-of-oscillators using only one detector and single electronic feedback-loop.
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Increasing the stability of nanofluids with cavitating flows in micro orifices
(AIP, 2016) Karimzadehkhouei, M.; Ghorbani, M.; Sezen, M.; Sendur, K.; Mengüç, Mustafa Pınar; Leblebici, Y.; Kosar, A.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
One of the most critical challenges for nanofluids in practical applications is related to their stability and reusability since a gradual agglomeration of nanoparticles in nanofluids occurs with time and is accelerated by heating. In this study, we propose a technique to maintain the performance and stability of nanofluids with the use of cavitating flows through micro orifices to prevent agglomeration and sedimentation of nanoparticles, which will increase the durability of the nanofluids. γ-Al2O3 (gamma-alumina) nanoparticles with a mean diameter of 20 nm suspended in water were utilized. In the current approach, a flow restrictive element induces sudden pressure, which leads to cavitation bubbles downstream from the orifice. The emerging bubbles interact with the agglomerated structure of nanoparticles and decrease its size through hitting or shock waves generated by their collapse, thereby increasing the stability and reusability of nanofluids. The method does not involve any use of expensive surfactants or surface modifiers, which might alter the thermophysical properties of nanofluids, may adversely influence their performance and biocompatibility, and may limit their effectiveness.
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MEMS cantilever sensor array oscillators: Theory and experiments
(Elsevier, 2016-01-01) Lulec, S. Z.; Adiyan, U.; Yaralıoğlu, Göksen Göksenin; Leblebici, Y.; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
This paper demonstrates that an array of cantilever sensors can be operated simultaneously at resonance using a single actuator and a single photodetector. Self-sustained oscillations (SSOs) of cantilevers can be achieved in a feed-back loop using gain saturation mechanism in the electronics. Multiple cantilevers require separate saturation mechanisms and separate sensing electronics for each channel. We introduced optical non-linearity using diffraction gratings at the tip of each cantilever which provide separate saturation non-linearity, enabling a single detector based oscillator array. Two-cantilever SSO operation is investigated analytically, and the multiple frequency oscillation criteria are established. Cross-coupling between the oscillation frequencies has been investigated by using this multi cantilever model. The proposed model will be helpful to design dynamic‑mode MEMS (Micro-electro-mechanical systems) cantilever sensor arrays with the desired functionality and cross-talk levels. This multiple SSO operation can be used in conjunction with dense cantilever arrays for various biosensor applications. Moreover, the model can also be useful to understand the operation of any kind of multiple simultaneous oscillator systems, which employs a single feed-back loop. We also present experimental results that confirm our model.