Browsing by Author "Orhan, Ezgi"

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Almanya'ya yapılan Türk işçi göçünün 51. yılında Almanya'daki Türklerin eğitim seviyeleri
(Bilkent University, 2012) Kök, Bora; Orhan, Ezgi; Kargalıoğlu, Fatih; Köseoğlu, Kıvanç; Kınay, Melis
Open Access
Mass and stiffness spectrometry of nanoparticles and bio-molecules by nanoelectromechanical systems
(2018-08) Orhan, Ezgi
Mass spectrometry (MS) is a technique used frequently in mass measurements in order to identify mass of the molecules. Nanoelectromechanical systems are highly sensitive to adhered species, thus using NEMS devices, it is possible to perform NEMS-MS where not only the inertial mass of the molecules but also the position of the adhered particle can be found out by resolving the adsorbateinduced frequency shifts in the first two modes.By using frequency shifts obtained from three mechanical modes, it is possible to obtain stiffness of the adsorbate in addition to its mass and position on the resonator when the Youngs modulus of the analyte and the resonant structure are comparable. For soft analytes, multimode information can be used to obtain shape properties of analytes and allows for image reconstruction from global image features. In order to conduct our experiments, we fabricate NEMS resonators whose transduction method is electrothermal actuation and piezoresistive detection. Fabrications of the devices are completed in National Nanotechnology Research Center (UNAM) in Bilkent University and Sabancı University Nanotechnology Research and Application Center (SUNUM).Initially, low vacuum apparatus is built to perform NEMS-MS using Electrospray Ionization(ESI) for molecule delivery. In order to direct particles to resonator, the fabrication of a doubly clamped beam is planned in a way that the orifice was etched through silicon wafer from the backside with KOH etch.This fabrication method, however, is tedious and hard to fabricate consistently.Then, Matrix Assisted Laser Desorption and Ionization (MALDI) is implemented to deliver particles towards the resonator.Different analyte types which are gold nanoparticles, centrosome organelles of HeLa cells and M13ke bacteriophages are used in the experiments.We use first four out-of-plane modes of the doublyclamped beam resonator for real-time study of the adsorbates. For biomolecule detection, care was taken to prevent uniform coverage of matrix molecules. Phaselocked-loop(PLL) operation is simultaneously performed for the first four modes of the resonator.Using frequency shifts of the four modes due to the adsorption, we propose a method in which we assume the analytes adhered on the beam are hemispherical to obtain mass and stiffness, size and positions of the analytes. Using three mechanical modes, stiffness, mass and position vaues are calculated.
Open Access
Nonlinear nanomechanical mass spectrometry at the single-nanoparticle level
(American Chemical Society, 2019) Yüksel, Mert; Orhan, Ezgi; Yanık, C.; Arı, Atakan B.; Demir, A.; Hanay, Mehmet Selim
Nanoelectromechanical systems (NEMS) have emerged as a promising technology for performing the mass spectrometry of large biomolecules and nanoparticles. As nanoscale objects land on NEMS sensors one by one, they induce resolvable shifts in the resonance frequency of the sensor proportional to their weight. The operational regime of NEMS sensors is often limited by the onset of nonlinearity, beyond which the highly sensitive schemes based on frequency tracking by phase-locked loops cannot be readily used. Here, we develop a measurement architecture with which to operate at the nonlinear regime and measure frequency shifts induced by analytes in a rapid and sensitive manner. We used this architecture to individually characterize the mass of gold nanoparticles and verified the results by performing independent measurements of the same nanoparticles based on linear mass sensing. Once the feasibility of the technique is established, we have obtained the mass spectrum of a 20 nm gold nanoparticle sample by individually recording about 500 single-particle events using two modes working sequentially in the nonlinear regime. The technique obtained here can be used for thin nanomechanical structures that possess a limited dynamic range.
Open Access
Piezoresistive silicon nanowire resonators as embedded building blocks in thick SOI
(Institute of Physics Publishing, 2018) Esfahani, M. N.; Kılınç, Y.; Karakan, M. Çağatay; Orhan, Ezgi; Hanay, M. Selim; Leblebici, Y.; Alaca, B. E.
The use of silicon nanowire resonators in nanoelectromechanical systems for new-generation sensing and communication devices faces integration challenges with higher-order structures. Monolithic and deterministic integration of such nanowires with the surrounding microscale architecture within the same thick crystal is a critical aspect for the improvement of throughput, reliability and device functionality. A monolithic and IC-compatible technology based on a tuned combination of etching and protection processes was recently introduced yielding silicon nanowires within a 10 μm-thick device layer. Motivated by its success, the implications of the technology regarding the electromechanical resonance are studied within a particular setting, where the resonator is co-fabricated with all terminals and tuning electrodes. Frequency response is measured via piezoresistive readout with frequency down-mixing. Measurements indicate mechanical resonance with frequencies as high as 100 MHz exhibiting a Lorentzian behavior with proper transition to nonlinearity, while Allan deviation on the order of 3-8 ppm is achieved. Enabling the fabrication of silicon nanowires in thick silicon crystals using conventional semiconductor manufacturing, the present study thus demonstrates an alternative pathway to bottom-up and thin silicon-on-insulator approaches for silicon nanowire resonators.