Browsing by Subject "MEMS"
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Item Open Access Airborne cmut cell design(Bilkent University, 2014) Yılmaz, AslıAll transducers used in airborne ultrasonic applications, including capacitive micromachined ultrasonic transducers (CMUTs), incorporate loss mechanisms to have reasonably wide frequency bandwidth. However, CMUTs can yield high efficiency in airborne applications and unlike other technologies, they offer wider bandwidth due to their low characteristic impedance, even for efficient designs. Despite these advantages, achieving the full potential is challenging due to the lack of a systematic method to design a wide bandwidth CMUTs. In this thesis, we present a method for airborne CMUT design. We use a lumped element circuit model and harmonic balance (HB) approach to optimize CMUTs for maximum transmitted power. Airborne CMUTs have narrowband characteristic at their mechanical part, due to low radiation impedance. In this work, we restrict the analysis to a single frequency and the transducer is driven by a sinusoidal voltage with half of the frequency of operation frequency, without any dc bias. We propose a new mode of airborne operation for CMUTs, where the plate motion spans the entire gap. We achieve this maximum swing at a specific frequency applying the lowest drive voltage and we call this mode of operation as Minimum Voltage Drive Mode (MVDM). We present equivalent circuit-based design fundamentals for airborne CMUT cells and verify the design targets by fabricated CMUTs. The performance limits for silicon membranes for airborne applications are derived. We experimentally obtain 78.9 dB//20Pa@1m source level at 73.7 kHz, with a CMUT cell of radius 2.05 mm driven by 71 V sinusoidal drive voltage at half the frequency. The measured quality factor is 120. CMUTs can achieve a large bandwidth (low quality factor level) as they can be manufactured to have thin plates. Low-quality-factor airborne CMUTs experience increased ambient pressure and therefore a larger membrane deflection. This effect increases the stiffness of the plate material and can be considered by nonlinear compliance in the circuit model. We study the interaction of the compliance nonlinearity and nonlinearity of transduction force and show that transduction overwhelms the compliance nonlinearity. To match the simulation results with the admittance measurements we implement a very accurate model-based characterization approach where we modify the equivalent circuit model. In the modified circuit model, we introduced new elements to include loss mechanisms. Also, we changed the dimension parameters used in the simulation to compensate the difference in the resonance frequency and amplitude.Item Open Access An analtical model for vibration analysis of disk resonator gyroscopes(Institute of Electrical and Electronics Engineers, 2022-06-08) Hosseini-Pishrobat, Mehran; Uzunoğlu, Baha Erim; Erkan, Derin; Tatar, ErdinçDisk resonator gyroscopes (DRGs) utilize the circular symmetry of a set of concentric rings to realize high-performance MEMS gyroscopes. We set forth an analytical method to calculate the mode shapes of the rings and then obtain the corresponding modal mass, Coriolis mass, and stiffness. Following the Ritz method, we minimize the total potential energy of the rings subject to the boundary conditions imposed by the spokes that connect the rings. We show the efficacy of our method using the frequency response of a fabricated DRG and comparison with the finite element method (FEM). With respect to the FEM, our modeling is more straightforward, more intuitive, and can be extended to model imperfections and ensuing effects such as quadrature error and frequency split.Item Open Access ANN-based estimation of MEMS diaphragm response: An application for three leaf clover diaphragm based Fabry-Perot interferometer(Elsevier BV, 2022-06-23) Yigit, E.; Hayber, Ş. E.; Aydemir, UmutIn this study, an artificial neural network (ANN) based model is developed for MEMS diaphragm analysis, which does not require difficult and time-consuming FEM processes. ANN-based estimator is generated for static pressure response (d) and dynamic pressure response (f) analysis of TLC (three leaf clover) diaphragms for Fabry-Perot interferometers as an example. TLC is one of the unsealed MEMS design diaphragms formed by three leaves of equal angles. The diaphragms used to train ANNs are designed with SOLIDWORKS and analyzed with ANSYS. A total of 1680 TLC diaphragms are simulated with eight diaphragm parameters (3 for SiO2 material, 4 for geometry, and 1 for pressure) to create a data pool for ANN’s training, validation, and testing processes. 80% of the data is used for training, 15% for validation, and the remaining for testing. Only four geometric parameters are used as input in the ANN estimator, and the material parameters are added to the model with an analytical multiplier. Thus, network models that estimate d and f values for all kinds of diaphragm materials are proposed, with a material-independently trained ANN structure. The performance of the ANN model is compared with the empirical equation suggested in the literature, and its superiority is demonstrated. In addition, the d and f parameters of TLC diaphragms designed with five different materials (Si, In2Se3, Ag, EPDM, Graphene) are estimated to be very close to the real ones. By using the proposed method, analyses of TLC diaphragms are quickly performed without the need for time-consuming and costly design and analysis programs.Item Open Access Batch-compatible micromanufacturing of a CMUT array for optoacoustic imaging of tissue-like phantoms(Bilkent University, 2021-08) Özyiğit, Doğu Kaan BuğraPhotoacoustic imaging (PAI), also named optoacoustic imaging, is a technol-ogy for medical imaging that relies on contrast data due to optical stimulation. Capacitive micromachined ultrasound transducers (CMUTs) are previously in-troduced for PAI applications. In this thesis, the provided CMUT array design has been partially micro-manufactured separately from electronics and a laser fiber light source while re-serving the necessary chip space for integration with electronics and laser fiber light source. Batch compatible wafer-scale microfabrication of CMUT arrays was done by a combination of novel as well as traditional MEMS microfabrication pro-cesses. CMUT array gaps, bottom electrodes, and insulation layer were formed on the Pyrex wafer using three separate photolithography masks. Anodic wafer bonding method is used for the formation of the top electrodes and top side of the gap heights of CMUT arrays. Process development for anodic wafer bonding between Pyrex wafers and SOI wafers has been done, where the Pyrex wafers have been previously processed with plasma etching, wet etching, metal stack de-position, insulation layer deposition, and insulation layer patterning, while SOI wafers have been used as received. Pyrex wafers and SOI wafers were anodically bonded to each other with developed anodic wafer bonding processes. After full completion of the micromanufacturing of the CMUT array chips, these CMUT ar-ray chips will be integrated with ASIC chips. Then, CMUT array chips and ASIC chips will be combined with a traditional printed circuit board (PCB). These in-tegrated CMUT array chips, ASIC chips, and PCB are going to be integrated with a fiber laser light source inside a mechanically robust hand-held probe that is planned to be used for optoacoustic imaging. The main goal of this CMUT array micromanufacturing study is to significantly contribute to the development of one of the necessary components for imaging of a tissue like-phantom using a hand-held imaging probe.Item Open Access Deep collapse mode capacitive micromachined ultrasonic transducers(Bilkent University, 2010) Olçum, SelimCapacitive micromachined ultrasonic transducers (CMUTs) are suspended microelectromechanical membrane structures with a moving top electrode and a rigid substrate electrode. The membrane is actuated by electrical signals applied between the electrodes, resulting in radiated pressure waves. CMUTs have several advantages over traditional piezoelectric transducers such as their wider bandwidth and microfabrication methodology. CMUTs as microelectromechanical systems (MEMS), are fabricated using CMOS compatible processes and suitable for batch fabrication. Low cost production of large amount of CMUTs can be fabricated using already established integrated circuit (IC) technology infrastructure. Contrary to piezoelectrics, fabricating large 2-D arrays populated with transducer elements using CMUTs is low-cost. The technological challenges of CMUTs regarding the fabrication and integration issues were solved during the past 15 years, and their successful operation has been demonstrated in many applications. However, commercialization of CMUTs is still an overdue passion for CMUT community. The bandwidth of the CMUTs are inherently superior to their piezoelectric rivals due to the nature of the suspended membrane structure, however, their power output capability must be improved to achieve superior signal-to-noise ratio and penetration depth. In this thesis, we gave a comprehensive discussion about the physics and functionality of CMUTs and showed both theoretically and experimentally that their power outputs can be increased substantially. Using the conventional uncollapsed mode of CMUTs, where the suspended membrane vibrates freely, the lumped displacement of the membrane is limited. Limited displacement, unfortunately, limits the power output of the CMUT. However, a larger lumped displacement is possible in the collapsed state, where the membrane gets in contact with the substrate. By controlling the movement of the membrane in this state, the power output of the CMUTs can be increased. We derived the analytical expressions for the profile of a circular CMUT membrane in both uncollapsed and collapsed states. Using the profiles, we calculated the forces acting on the membrane and the energy radiated to the medium during an applied electrical pulse. We showed that the radiated energy can be increased drastically by utilizing the nonlinear forces on the membrane, well beyond the collapse voltage. Using the analytical expressions, we developed a nonlinear electrical equivalent circuit model that can be used to simulate the mechanical behavior of a transmitting CMUT under any electrical excitation. Furthermore, the model can handle different membrane dimensions and material properties. It can predict the membrane movement in the collapsed state as well as in the uncollapsed state. In addition, it predicts the hysteretic snap-back behavior of CMUTs, when the electric potential across a collapsed membrane is decreased. The nonlinear equivalent circuit was simulated using SPICE circuit simulator, and the accuracy of the model was tested using finite element method (FEM) simulations. Better than 3% accuracy is achieved for the static deflection of a membrane as a function of applied DC voltage. On the other hand, the pressure output of a CMUT under large signal excitation is predicted within 5% accuracy. Using the developed model, we explained the dynamics of a CMUT membrane. Based on our physical understanding, we proposed a new mode of operation, the deep collapse mode, in order to generate high power acoustic pulses with large bandwidth (>100% fractional) at a desired center frequency. We showed both by simulation (FEM and equivalent circuit) and by experiments that the deep collapse mode increases the output pressure of a CMUT, substantially. The experiments were performed on CMUTs fabricated at Bilkent University by a sacrificial release process. Larger than 3.5 MPa peak-to-peak acoustic pulses were measured on CMUT surface with more than 100% fractional bandwidth around 7 MHz using an electrical pulse amplitude of 160 Volts. Furthermore, we optimized the deep collapse mode in terms of CMUT dimensions and parameters of the applied electrical pulse, i.e., amplitude, rise and fall times, pulse width and polarity. The experimental results were compared to dynamic FEM and equivalent circuit simulations. We concluded that the experimental results are in good agreement with the simulations. We believe that CMUTs, with their high transmit power capability in the deep collapse mode can become a strong competitor to piezoelectrics.Item Open Access Design of a high-resolution microfluidic microwave MEMS phase shifter(Wiley, 2011) Ozbey, B.; Ozturk, S.; Aktas, O.In this article, a novel microwave microelectromechanical phase shifter based on a microfluidic design is proposed and demonstrated. The design principles, the fabrication process, and experimental results (S-parameters and phase shift plots) are presented. The proposed system has a high bandwidth, high-power handling capacity, and a high-resolution along with a small settling time.Item Open Access Design, fabrication and operation of a very high intensity CMUT transmit array for beam steering applications(Bilkent University, 2020-12) Khan, Talha MasoodSeveral studies have reported airborne ultrasound transmission systems focused on achieving beamforming. However, beam steering and beamforming for capacitive micromachined ultrasonic transducers (CMUTs) at high intensity remains to be accomplished. CMUTs, like other ultrasonic transducers, incorporate a loss mechanism to obtain a wide bandwidth. They are restricted to a limited amount of plate swing due to the gap between the radiating plate and the bottom electrode, along with a high dc bias operation. CMUTs can be designed to produce high-intensity ultrasound by employing an unbiased operation. This mode of operation allows the plate to swing the entire gap without collapsing, thus enabling higher intensity. In this study, we use an equivalent circuit-based model to design unbiased CMUT arrays driven at half the mechanical frequency. This model is cross verified using finite element analysis (FEA). CMUT arrays are produced in multiple configurations using a customized microfabrication process that involves anodic wafer bonding, a single lithographic mask, and a shadow mask. We use impedance measurements to characterize the microfabricated devices. We experimentally obtained the highest reported intensity using a microfabricated 2×2 CMUT array driven at resonance in a pulsed configuration. This array is also capable of beam steering and beamforming at a high intensity such that it can steer the entire half-space. The beam obtained from the array is in excellent agreement with the theoretical predictions. The amplitude and phase compensation for the devices remain constant that makes these arrays attractive for applications involving park assist, gesture recognition, and tactile displays.Item Open Access Designing, fabrication and post- fabrication characterization of half-frequency driven 16 x 16 waterborne transmit CMUT array(Bilkent University, 2021-02) Abhoo, Yusuph AbubakarCapacitive Micromachined Ultrasonic Transducers (CMUT) are micro-scaled electromechanical devices which are used to either transmit or receive pressure signals and applicable for various purposes such as ultrasonic sensor, medical imaging, accurate biometric sensing and parametric speakers. For transmitting CMUT transducer, different sizes and array configurations are used to intensify the transmission power depending on the application. The half-frequency driven waterborne transmitting CMUT array designed in this work is to be used for high resolution volumetric medical imaging purpose. This was accomplished by a design which prioritizes maximizing the power output, achieving a directive radiation pattern with low sidelobes which maximizes the beamformable region. In this work, the issues with steering of the focused beam are also resolved to achieve a focused steerable beam. This work is an advancement from the earlier designed half-frequency driven airborne transmit CMUT to improve power output, introduce the beamforming and focused transmission capabilities and be applicable for high resolution volumetric medical imaging purpose. To improve the power output, the design was made to compensate for the static depression. Compensating for static depression was achieved by designing to operate the CMUT without DC bias voltage which allows for full-gap swing and giving output signal of twice the input frequency. This property allows the cell to produce high power output with low voltage levels but also brings the advantage of operating the cell with very high voltages without collapsing. The CMUT was chosen to be operating at 7.5 MHz and be driven by Digital Phased Array System (DiPhAS) which allowed to have maximum of 256 channels which for volumetric transmission meant a maximum of 16 x 16 array. Since the radiation pattern and Rayleigh distance are both the functions of radius, frequency and the pitch, the design optimization was found while considering all the above preferences simultaneously. The cells’ radii were determined to be 80 µm, the plate thickness was 15 µm, the gap height was found to be 117 nm and the pitch was 192 µm. The array designing was carried out using the large-signal equivalent circuit model and the radiation impedance matrix phenomenon. The simulations showed that with this design, the maximized Rayleigh distance was 45.3 mm and the sidelobe of -17.4 dB. In simulations, very high pressure outputs were achievable with individual cells up to 425 kPa per cell with 150 VPP input while up to 1.5 MPa was emitted by the array plane wave transmission with only 10 VPP input and almost doubles when the transmitted beam was focused at zero degrees. Fabrication was done by the wafer boding and flip-chip bonding techniques where the whole process required only two lithography masks. After fabrication, the tests were performed to identify the yield of the transducer was 18.75% of the array then impedance analysis was done to characterize the functional cells and resonance frequency drift. The transducer was cased in a water-tight manner and the waterborne transmission were done with individual cells to characterize and compare the performance with the design simulations which were in the range of agreement achieving an average of 1625 Pa per cell. The functional cells were then used for plane wave transmission with 10 VPP and the output pressure of 397 kPa was achieved at resonance frequency. The measurement results showed that the design could further be improved by compensating the active area to improve the yield for better results and be able to use it for high resolution 3D medical imaging.Item Open Access Electrically unbiased and half frequency driven waterborne 16×16-element 2-D phased array CMUT(Bilkent University, 2019-08) Enhoş, KeremCapacitive micromachined ultrasonic transducers (CMUT) are typically used as arrays consisting of separate cells or interconnected sub arrays, and these cells have several operation modes. Design procedure and measurements have been previously presented for an airborne CMUT cell without a DC bias. In unbiased mode, the plate motion spans the entire gap without collapsing. The frequency of sinusoidal electrical input signal is half of the resulting acoustical output signal. A large plate swing can be obtained at low excitation voltages using the entire remaining gap. In this work, a design procedure of arrays with unbiased operation mode is derived. Designs are validated by means of simulations and measurements on fabricated CMUTs. The problems associated with beamforming are resolved. Use of this operation mode in an array configuration enables larger acoustical power output. A better transmitted signal waveform definition is obtained when pulse width modulation (PWM) is employed. In the design process of CMUTs, large-signal equivalent circuit model is used. In order to have volumetric transmission, a 16×16 (256 elements) phased array configuration is chosen. A design procedure is presented considering the radiation pattern, Rayleigh distance and the parameters of the lumped-element model. This procedure is applied for designing two arrays, with resonance frequencies at 7.5 MHz and at 18.5 MHz. Harmonic balance and transient analyses are carried out with Gaussian enveloped tone burst, transient sinusoidal and PWM signals with different duty cycles. Outputs of these simulations are fed in beamforming toolboxes for further verification. Corresponding experimental measurements are conducted on an ultrasound measurement system. The dimensions of the CMUT elements in the array are determined as 80 μm element radius, 15 μm plate thickness, and 171 nm effective gap height at 7.5 MHz, where the center-to-center inter-element pitch is set at 192 μm. The array is designed such that it has maximum Rayleigh distance of 45.3 mm, while having a maximum sidelobe level of −17.4 dB. According to these specifications, CMUT array is manufactured using wafer scale batch compatible production. Only two lithography masks, which require conventional photolithography steps, are used in production. The vibrating plate is constructed with anodic wafer bonding and the fabricated CMUT array chip is integrated to PCB with flip-chip bonding. Measurements are conducted for this novel device by integrating the CMUT array chip manufactured with MEMS techniques and conventional macro scale manufactured PCB by using impedance analyser.Item Open Access Ferroelectric based microgyroscope for inertial measurement unit: Modeling and simulation(IEEE, 2012) Ozer, Z.; Mamedov, Amirullah M.; Özbay, EkmelThis paper present the design and modeling of the micro-electromechanical systems (MEMS) on the ternary ferroelectric compounds (PZT and Ba xSr 1-xTiO 3) based by using finite element model (FEM) simulation. © 2012 IEEE.Item Open Access In-chip microstructures and photonic devices fabricated by nonlinear laser lithography deep inside silicon(Nature Publishing Group, 2017) Tokel, O.; Turnalı, A.; Makey, G.; Elahi, P.; Çolakoǧlu, T.; Ergeçen E.; Yavuz, Ö.; Hübner R.; Borra, M. Z.; Pavlov, I.; Bek, A.; Turan, R.; Kesim, D. K.; Tozburun, S.; Ilday, S.; Ilday, F. Ö.Silicon is an excellent material for microelectronics and integrated photonics 1-3, with untapped potential for mid-infrared optics 4 . Despite broad recognition of the importance of the third dimension 5,6, current lithography methods do not allow the fabrication of photonic devices and functional microelements directly inside silicon chips. Even relatively simple curved geometries cannot be realized with techniques like reactive ion etching. Embedded optical elements 7, electronic devices and better electronic-photonic integration are lacking 8 . Here, we demonstrate laser-based fabrication of complex 3D structures deep inside silicon using 1-μm-sized dots and rod-like structures of adjustable length as basic building blocks. The laser-modified Si has an optical index different to that in unmodified parts, enabling the creation of numerous photonic devices. Optionally, these parts can be chemically etched to produce desired 3D shapes. We exemplify a plethora of subsurface - that is, 'in-chip' - microstructures for microfluidic cooling of chips, vias, micro-electro-mechanical systems, photovoltaic applications and photonic devices that match or surpass corresponding state-of-the-art device performances.Item Open Access Low-voltage small-size double-arm MEMS actuator(2009) Bıyıklı, Necmi; Damgaci, Y.; Cetiner, B.A.The fabrication and characterisation of a double-arm cantilever-type metallic DC-contact MEMS actuator with low pull-down voltage are reported. Bi-layer TiW cantilevers with an internal stress gradient were fabricated using a microwave-compatible fabrication process. Owing to its small size, cantilever length (L=5-50m) and width (W=2-40m), i.e. ∼10-100 times smaller in lateral dimensions than a standard MEMS actuator, this actuator showed actuation voltages lower than 10 V. RF measurements of the 10m-wide actuators yielded an average insertion loss less than 1dB and isolation higher than 40dB up to 25GHz. The developed actuator is well suited for integration in reconfigurable microwave circuits and systems such as reconfigurable antennas and arrays. © 2009 The Institution of Engineering and Technology.Item Open Access Lumped element modeling of circular CMUT in collopsed mode(Bilkent University, 2014) Aydoğdu, ElifCapacitive micromachined ultrasonic transducer is a microelectromechanical device, which serves as an acoustic signal source or sensor, in a variety of applications including medical ultrasound imaging, ultrasound therapy, airborne applications. It has a suspended membrane with an electrode inside, and at the underlying substrate there is another electrode, so that the membrane can be deflected by the electrical field formed between the electrodes. Similarly, any mechanical disturbance on the membrane can be sensed as a change in the capacitance of the two electrodes. CMUT is a nonlinear device which has a distributed mechanical operation. Although, it is a mass-spring system basically, the nonlinear electrical force and the radiation force makes it impossible to solve CMUT through analytical equations. In order to predict its behavior, and design a CMUT towards the needs of a specific application, either finite element analysis or equivalent electrical circuit modeling should be utilized. Finite element analysis (FEA) can predict the distributed CMUT operation with high accuracy, but its usage is limited to designs employing low number of CMUTs because of the computation cost. Recently, advances in equivalent circuit modeling, made it possible to simulate arrays employing very high number of CMUTs, with high accuracy. These models assume uncollapsed mode operation and except collapsed mode operation as it is highly nonlinear. This thesis focuses on obtaining an accurate equivalent circuit model for a circular CMUT in collapsed mode. The outcome is a parametric circuit model, that can simulate a CMUT of any physical and material parameters, under an arbitrary electrical or mechanical excitation. In collapsed mode, the compliance of the membrane is no longer constant as in uncollapsed mode, and it increases with increasing contact radius. Similarly, the capacitance, the electrical force and the radiation impedance all have new behavior regarding the contact radius. As there is no analytical solution for those parameters, we perform numerical calculations and extract expressions for each of them. First, we calculate the collapsed membrane deflection, utilizing the exact electrical force distribution in the analytical formulation of membrane deflection. Then we use the deflection profile to calculate the capacitance, electrical force, and compliance. Performing a set of calculations for different CMUT dimensions, different pressure and voltage levels, we obtain dependencies of those parameters on rms deflection. Then we develop a lumped element model of collapsed membrane operation, expressing the parameters as functions of rms deflection. The radiation impedance for the collapsed mode is also included in the model. The model is then merged with the uncollapsed mode model to obtain a simulation tool that handles all CMUT behavior, in transmit or receive. Large- and smallsignal operation of a single CMUT can be fully simulated for any excitation regime. The results are in good agreement with FEM simulations.Item Open Access MEMS based ultrasonic gas sensor with universal sensing capability(Bilkent University, 2023-09) Erkan, DerinGas sensors are a critical technology for life safety, process control, and most recently air quality measurements. Currently utilized gas sensing technologies need to be tailored to each specific gas, using either a chemically reactive substrate or an optical detector sensitive to certain gas types, providing very good selectivity at the expense of flexibility. In contrast, acoustic sensors promise a potentially universal method of gas sensing with lower selectivity, by measuring the speed of sound in a resonant cavity and inferring the gas content. In this work, a proof of concept for a MEMS based acoustic gas sensor is proposed. A horizontal cavity allows for a compact design, compared to vertical designs shown in the literature. Fabrication is simplified compared to existing CMUT/PMUT designs by using electrically tunable in-plane resonators as transducers. Fabrication of the designed sensor is carried out using an in-house developed SOI-MEMS process, while acoustic cavities are fabricated from silicon. During operation, one resonator excites the cavity while the other resonator measures the response. Frequency sweeps of the resonators while varying the tuning allows full characterization of device response. Overlaying sweeps at different tuning parameters reveals the cavity response, while testing with no cavity rules out parasitic effects. Both speed of sound and quality factor are observed, which can be used to improve selectivity in gas mixtures. The proof of concept device is tested in ambient air, measuring the speed of sound in air as 342 m/s, consistent with the literature and with external measurements.Item Open Access Mic-in-CMOS: CMUT as a sealed-gap capacitive microphone(IEEE, 2020) Köymen, Hayrettin; Ahiska, Y.; Atalar, Abdullah; Köymen, I.; Taşdelen, A .Sinan; Yılmaz, MehmetThe design and production of a CMOS compatible, watertight and ingress-proof CMUT (capacitive micromachined ultrasonic transducer) microphone, mic-in-CMOS, with vacuum-gap is described. We present an analytical model-based approach for the design of mic-in-CMOS, where a basis for quantitative comparison of performance trade-offs is provided. The sealed vacuum gap of the mic-in-CMOS is basically a lossless sensor, free of mechanical noise. Its SNR is determined by the noise of the pre-amplification electronics (the noise contributor in a CMUT with vacuum gap is essentially the radiation resistance, which is less than 0 dBA for audio band for a 1 mm2 device). The design of mic-in-CMOS involves many multilateral trade-offs such as gap height vs membrane thickness vs sensitivity vs need for linear operation vs bias voltage and atmospheric depression, to name few. The mic-inCMOS design can be mass produced using CMOS film stacks only, as such the fabrication process can be carried out entirely in a CMOS processes production line complemented with CMOS compatible post-processing approaches. Mic-inCMOS has the advantage of low production cost with minimal packaging requirement and on-die EMI / EMC.Item Open Access Microcantilever based disposable viscosity sensor for serum and blood plasma measurements(2013) Cakmak O.; Elbuken, C.; Ermek, E.; Mostafazadeh, A.; Baris I.; Erdem Alaca, B.; Kavakli I.H.; Urey H.This paper proposes a novel method for measuring blood plasma and serum viscosity with a microcantilever-based MEMS sensor. MEMS cantilevers are made of electroplated nickel and actuated remotely with magnetic field using an electro-coil. Real-time monitoring of cantilever resonant frequency is performed remotely using diffraction gratings fabricated at the tip of the dynamic cantilevers. Only few nanometer cantilever deflection is sufficient due to interferometric sensitivity of the readout. The resonant frequency of the cantilever is tracked with a phase lock loop (PLL) control circuit. The viscosities of liquid samples are obtained through the measurement of the cantilever's frequency change with respect to a reference measurement taken within a liquid of known viscosity. We performed measurements with glycerol solutions at different temperatures and validated the repeatability of the system by comparing with a reference commercial viscometer. Experimental results are compared with the theoretical predictions based on Sader's theory and agreed reasonably well. Afterwards viscosities of different Fetal Bovine Serum and Bovine Serum Albumin mixtures are measured both at 23. °C and 37. °C, body temperature. Finally the viscosities of human blood plasma samples taken from healthy donors are measured. The proposed method is capable of measuring viscosities from 0.86. cP to 3.02. cP, which covers human blood plasma viscosity range, with a resolution better than 0.04. cP. The sample volume requirement is less than 150. μl and can be reduced significantly with optimized cartridge design. Both the actuation and sensing are carried out remotely, which allows for disposable sensor cartridges. © 2013 .Item Open Access Modeling and simulation of the ferroelectric based micro gyroscope: FEM analysis(Taylor and Francis, 2013-09-23) Ozer, Z.; Mamedov, Amirullah M.; Özbay, EkmelThis paper presents the design and modeling of micro-electromechanical systems (MEMS) on the ternary ferroelectric compounds (PZT) based by using finite element model (FEM) simulation. The conceptual framework establishes five steps to perform the critical analysis: design a novel structure, define the failure mechanisms under the given conditions, analyze different vibrations, analyze the operation principle, and detect resonance modes. In addition, MEMS failure modes were analyzed under different scenarios and the obtained results discussed. Copyright © Taylor & Francis Group, LLC.Item Open Access Multiple electrically tunable parametric resonances in a capacitively coupled electromechanical resonator for broadband energy harvesting(Institute of Physics Publishing Ltd., 2021-03-12) Surappa, S.; Erdoğan, Tuna; Degertekin, L. F.Parametric excitation (PE) has widely been employed as a method of mechanical pre-amplification in nonlinear vibration energy harvesting systems. However, despite their advantages, most current PE systems are limited to degenerate parametric operation within a narrow frequency band around the primary instability tongue. In this paper, we simulate and experimentally demonstrate a parametrically driven capacitive electromechanical resonator having multiple electrical degrees of freedom. Multiple modes allow for several frequency bands in which the electrical resonator is driven into nondegenerate (combination) parametric resonance (PR) in addition to degenerate resonance, thereby enabling operation over a broader range of frequencies while maintaining the same mechanical footprint. These frequency bands and PR thresholds are tunable by simply changing the electrical circuit parameters and PR can be achieved in the presence of high mechanical damping making the method more adaptable than purely mechanical approaches. Experimental results are extended by simulations indicating that proper selection of operating parameters can enable the merging of instability tongues to produce a broadband region of PR for elastic wave energy harvesting thereby obtaining superior performance when compared to an equivalent single degree of freedom PE energy harvester.Item Open Access Nanoelectromechanical switches for reconfigurable antennas(2010) Cetiner, B.A.; Bıyıklı, Necmi; Yildirim, B.S.; Damgaci, Y.We report on the full-wave analyses of a frequency reconfigurable antenna integrated with metallic nanoelectromechanical system (NEMS) switches (length = 3 μm, width = 60 nm). The NEMS switch used in this work has the same architecture with low voltage, double-arm cantilever-type metallic DC-contact microelectromechanical system (MEMS) switch recently developed in author's group. The microfabrication and characterization of the MEMS switch have also been given in this article. Copyright © 2009 Wiley Periodicals, Inc.Item Open Access Nanomechanical motion transducers for miniaturized mechanical systems(MDPI AG, 2017) Kouh, T.; Hanay, M. S.; Ekinci, K. L.Reliable operation of a miniaturized mechanical system requires that nanomechanical motion be transduced into electrical signals (and vice versa) with high fidelity and in a robust manner. Progress in transducer technologies is expected to impact numerous emerging and future applications of micro- and, especially, nanoelectromechanical systems (MEMS and NEMS); furthermore, high-precision measurements of nanomechanical motion are broadly used to study fundamental phenomena in physics and biology. Therefore, development of nanomechanical motion transducers with high sensitivity and bandwidth has been a central research thrust in the fields of MEMS and NEMS. Here, we will review recent progress in this rapidly-advancing area.