Electrical & Electronics Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10679/44

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Browsing by Author "Adiyan, U."

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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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    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.
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    A prism-based non-linear optical readout method for MEMS cantilever arrays
    (Elsevier, 2016-10-15) Adiyan, U.; Civitci, F.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    This paper demonstrates the use of a single right-angle prism for the optical readout of micro-electro-mechanical systems (MEMS) cantilever arrays. The non-linear reflectivity arisen from the internal reflection at the right-angle prism’s hypotenuse plane enables the measurement of cantilever deflections. The cantilever arrays used in the experiments are made of electroplated nickel structures and actuated at resonance by an external electro-coil. A laser beam illuminates multiple cantilevers, and then it is partially reflected by the prism. The prism reflectivity changes with the cantilever deflection and modulates the laser intensity at the photodetector. The detection sensitivity of the optical readout system is determined by the initial angle of incidence at the prism’s hypotenuse plane, numerical aperture of the illumination system and the polarization of the laser beam. In this paper, we showed both theoretically and experimentally that self-sustained oscillations of two MEMS cantilevers with simple rectangular geometry is achievable using only one actuator and one photodetector. The gain saturation mechanism for the oscillators was provided by the optical non-linearity in the prism readout, which eliminates the requirement for separate sensing electronics for each cantilever. Based on our analytical and experimental data, we found that the prism incident angle around 41.2° is desirable in the closed-loop system due to high responsivity. Finally, we demonstrated simultaneous self-sustained oscillations of two cantilevers in closed-loop with resonant frequencies in the range 25–30 kHz. It was shown that multiple oscillations are obtainable if the cantilever resonant frequencies are separated from each other by at least 3 dB bandwidth.