Browsing by Subject "Electrothermal Actuation"
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Item Open Access Design, fabrication, and applications of multi-mode nanoelectromechanical systems(Bilkent University, 2017-07) Arı, Atakan BekirMiniaturization of systems allowed wide spread consumer use of microelectronics, integrated circuits and MEMS based sensors. Thanks to the advancement in microfabrication methods, it is possible to build structures with submicron dimensions. The integration of electronic control to these submicron structures started the NEMS eld. Due to their minuscule dimensions and very high frequency response, NEMS can sense external perturbations with unprecedented sensitivity. This made NEMS excellent candidates for sensor applications. NEMS are starting to evolve from academic research tools to become mass produced and large scale integrated sensing devices. Information extracted from the higher order modes further increase the capabilities of NEMS. In order to attain this extra information, we fabricated NEMS that can reach higher order mechanical modes. Every step of fabrication was done at Bilkent University research facilities such as UNAM and ARL. To pattern the submicron feature sizes, we relied on electron beam lithography. Thermal and electron beam evaporators were deployed for metallization of contacts and etch mask. In order to suspend the doubly clamped beams, we developed anisotropic silicon nitride and isotropic silicon dry etch recipes. At each step of the fabrication, tools such as SEM and stylus pro lometer was utilized for characterization. Fabricated NEMS were wirebonded to printed circuit boards for detection. Electrothermal actuation, an integrated method, was chosen to drive the nanomechanical resonator to its higher order modes. Piezoresistive down-mixing, another integrated method to complement the actuation, was used to detect the resulting nanomechanical motion. We used high frequency electronic equipment to detect RF range responses of our NEMS. Using these NEMS, we studied two novel applications on intermodal and mechanical coupling. First, we investigated intermodal coupling e ect of doubly clamped beams in order utilize this coupling e ect in higher order mode detection. When a doubly clamped beam is excited at its resonance frequency, every other mode of the device gets tuned. This occurs due to the clamping on both sides preventing longitudinal elongation and causing a stress on the beam. Using intermodal coupling method, we probed higher order modes of a nanomechanical resonator while tracking the fundamental frequency at the same time. We were able to detect mechanical modes up to 840 MHz, well out of the detection limit of our setup. We propose intermodal coupling as a novel detection method to acquire frequency response of NEMS at higher order modes which can not be detected with conventional methods. Finally, we studied nano scale energy sinks that absorb energy from a another structure. Energy sinks are linear oscillators that can trap the energy of a nearby structure within their phase space. When the natural frequency of these sinks are distributed optimally, nite number of sinks can mimic absorption of in nite sinks. We envisioned a real time dissipation controlled NEMS platform by deploying energy sinks. In order to test energy sink performance at nano scale, we devised an experimental setup, comparing identical nanomechanical resonators with and without energy sinks. We have shown that energy sinks successfully absorb energy of a resonator at nanoscale.Item Open Access Mass and stiffness spectrometry of nanoparticles and bio-molecules by nanoelectromechanical systems(Bilkent University, 2018-08) Orhan, EzgiMass 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.