Browsing by Subject "Buckling"
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Item Open Access Design and fabrication of CSWAP gate based on nano-electromechanical systems(Springer, Cham, 2016) Yüksel, Mert; Erbil, Selçuk Oğuz; Arı, Atakan B.; Hanay, M. SelimIn order to reduce undesired heat dissipation, reversible logic offers a promising solution where the erasure of information can be avoided to overcome the Landauer limit. Among the reversible logic gates, Fredkin (CSWAP) gate can be used to compute any Boolean function in a reversible manner. To realize reversible computation gates, Nano-electromechanical Systems (NEMS) offer a viable platform, since NEMS can be produced en masse using microfabrication technology and controlled electronically at high-speeds. In this work-in-progress paper, design and fabrication of a NEMS-based implementation of a CSWAP gate is presented. In the design, the binary information is stored by the buckling direction of nanomechanical beams and CSWAP operation is accomplished through a mechanism which can selectively allow/block the forces from input stages to the output stages. The gate design is realized by fabricating NEMS devices on a Silicon-on-Insulator substrate. © Springer International Publishing Switzerland 2016.Item Open Access Design, fabrication, and applications of electrostatically buckled nanomechanical systems(Bilkent University, 2018-08) Erbil, Selçuk OğuzBuckling is an important resource for memory and sensing applications at the micro- and nano-scale. Although di erent approaches have been developed to access buckling, such as the use of pre-stressed beams or thermal heating, none of them can dynamically and precisely control the critical bifurcation parameter |the compressive stress on the nanobeam| while keeping the heat generation and power dissipation at levels acceptable for real-life applications. Here, we develop an all-electrostatic architecture to control the compressive force, as well as the direction and amount of buckling, without heat generation. The devices, consisting of contact pads, comb-drive and beam, have been fabricated on Silicon on Insulator (SOI) chip by using micro-/nano-fabrication techniques. With this architecture, we demonstrated fundamental aspects of device function and dynamics. By applying signal voltages as low as 0.5 V, we controlled the direction of buckling to store binary information. Lateral de ections as large as 12% of the beam length were achieved, allowing nanomechanical manipulations at large deformations. We performed fatigue tests on the device which showed no discernible damage even after 10,000 buckling cycles. By modulating the compressive stress and lateral electrostatic force acting on the beam, we tuned the potential energy barrier between the post-bifurcation stable states and observed persistent transitions between the states. The proposed architecture, in this work, opens avenues for developing DC-controlled multibit nanomechanical logic gates, nano-manipulators, switches, and for studying the relationship between entropy and information.Item Open Access An experimental approach to nanomechanical buckling and snap-through phenomenon(Bilkent University, 2019-08) Hatipoğlu, UtkuBuckling has received little attention as a valuable resource for engineering applications since it is regarded as a type of failure in civil and mechanical engineering. Nevertheless, buckling has a great potential in nanoelectromechanical systems(NEMS) field as a bistable process that has rich and complex dynamics. Here, we explore post buckling dynamics of a nano-beam experimentally by employing various probing techniques. By employing an all-electronic architecture, we precisely control the buckling amount as well as buckling direction of the nano-beam which eventually gives us the ability to control a two-level mechanical system with high precision and speed. A full control over the potential energy landscape of the system is demonstrated with different techniques such as Scanning Electron Microscopy operated in three different modes and microwave coupling method. During proof of concept experiments, left and right buckling, large deflection buckling, nonvolatility – which is an indication of pure bistable states – and snap-through phenomenon is demonstrated. Further steps of the study focused on the snap-through phenomenon that is the interstate transitions of the buckling beam after bifurcation. During these experiments, more involved relations are investigated such as mechanical bias and effect of plastic deformation as well as the effect of actuation scheme on interstate jumps. Moreover, to obtain a better grasp of post-buckling dynamics, quantitative measurements are carried out which reveal the reaction speed of the system and time scale of interstate jumps. Lastly, oscillatory snap-through motion is observed in some special conditions that can be beneficial to understand noise dynamics of the system and it has a potential to contribute energy harvesting applications.Item Open Access From beams to bilayers: A unifying approach towards instabilities of compressible domains under plane deformations(Elsevier Ltd, 2021-10) Bakiler, A. Derya; Dörtdivanoğlu, B.; Javili, AliInstabilities that form when a domain of compliant elastic material goes under compressive forces are prevalent in nature and have found many applications. Even though instabilities are observed in a myriad of fields and materials, the large deformation bifurcation analysis of compressible domains, may it be beams, half-spaces, or bilayers, remains understudied compared to the incompressible case. In this work, we present a unifying approach for the instability analysis of a compressible elastic domain under plane deformations, wherein the unifying approach is then particularized for beams, half-spaces, and bilayers. First, the large-deformation incremental analysis for a rectangular, compressible, hyperelastic domain under plane deformations is developed, which serves as a generic and all-encompassing framework for other geometries. Subsequently, this generic framework is applied to the specific domains of beam, half-space, and lastly as the superimposition of the two; bilayer. Obtained analytical results for the onset of wrinkling in the beam, half-space and bilayer geometries are explored in the full range of compressibility and for various geometrical parameters, including their comparison with computational simulations using the finite element method, cultivating excellent agreements between analytical and numerical results all across the material and geometrical parameter spectrum. The analytical framework presented here provides grounds for further works on other modes of instabilities and more complex geometries.Item Open Access Full electrostatic control of nanomechanical buckling(American Physical Society, 2020) Erbil, Selçuk Oğuz; Hatipoğlu, Utku; Yanık, C.; Ghavami, Mahyar; Arı, Atakan B.; Yüksel, Mert; Hanay, Mehmet SelimBuckling of mechanical structures results in bistable states with spatial separation, a feature desirable for sensing, shape configuration, and mechanical computation. Although different approaches have been developed to access buckling at microscopic scales, such as heating or prestressing beams, little attention has been paid so far to dynamically control all the parameters critical for the bifurcation—the compressive stress and the lateral force on the beam. Here, we develop an all-electrostatic architecture to control the compressive force, as well as the direction and amount of buckling, without significant heat generation on micro- or nanostructures. With this architecture, we demonstrated fundamental aspects of device function and dynamics. By applying voltages at any of the digital electronics standards, we have controlled the direction of buckling. Lateral deflections as large as 12% of the beam length were achieved. By modulating the compressive stress and lateral electrostatic force acting on the beam, we tuned the potential energy barrier between the postbifurcation stable states and characterized snap-through transitions between these states. The proposed architecture opens avenues for further studies in actuators, shape-shifting devices, thermodynamics of information, and dynamical chaos.Item Open Access Monitoring micromechanical buckling at high-speed for sensing and transducer applications(IEEE, 2021-08-06) Demiralp, Berke; Pisheh, Hadi Sedaghat; Küçükoğlu, Berk; Hatipoğlu, Utku; Hanay, Mehmet SelimControlling the amount and direction of buckling at micro- and nano-scale efficiently opens up avenues for novel actuation and sensor applications. Earlier platforms that can achieve a full and non-thermal control of microscopic buckling operated only with a time resolution of 40 ms. Here, we have measured the buckling amount of a beam starting from unbuckled position and reaching to large post-buckling deformations by collecting secondary electrons under scanning electron microscope. Line mode is used for ultrafast measurements with 33kHz scan frequency, and a displacement noise floor of 40pm/√Hz was obtained. Moreover, by further reduction in the device dimensions, the buckling threshold voltage was reduced by a factor of three compared to similar platforms.Item Open Access Nanomechanical buckling for applications in nonlinear dynamics(Bilkent University, 2021-07) Demiralp, BerkeThere has not been enough attention on post buckling behavior at nano scale even though it reveals rich nonlinear and chaotic dynamics and has potential to be used on cutting edge sensing, actuation, computation and communication applications. Here, full motion of the nanomechanical buckling, starting from un-buckled position to large deformations at post buckling regime has been precisely measured with error bars of ±7 nm for large deformation regime and ±2.8 nm for √ initial bending, with a noise floor of 38.5 pm/ Hz. Line mode of SEM is used for deflection detection which uses secondary electrons collected from sample and relevant code is developed for data processing. Initial bending, initial buckling and inflection point are well defined which can help us to understand transition to post buckling regime and development of sensors and actuators. Additionally, one well oscillation, double well oscillation and chaotic trajectories are investi-gated using the system as forced double well oscillator. Trajectory plotting is performed with an image processing code which benefits from contrast difference of the device and environment. A new region within double well oscillation regime is observed where motion converts from one well oscillation to double well oscilla-tion which could be a candidate on mechanical computation and communication applications. Also, a preliminary design for synchronized chaos experiments using the same buckling platform is developed. Finally, an optomechanical experimental setup and chip is built for measure-ment of one or multiple NEMS beams. Fiber optic techniques are used for exper-imental setup and grating couplers, ring/racetrack resonators are develoxper-imental setup and grating couplers, ring/racetrack resonators are developed for beam measurements. Critical couplings on multiple devices are observed.Item Open Access Pre- and post-buckling analysis of nanobeams(Bilkent University, 2019-02) Vardar, OnurInterest in nanobeams is increasing as their application areas widen and new properties are discovered. These structures exhibit size dependent intrinsic properties that are absent in macroscale. This requires employment of new material models as bulk models by themself are not sufficient to describe the physics unless one considers the domain as a composite material, which is undesirable. In this work it was confirmed that incorporation of surface elasticity results in a good match with experiments. Moreover it was shown that due to lack of out-of-plane shear support of surfaces and curves, Euler beam assumptions fail for numerical implementations when the beam size reduces. This phenomenon was shown to be a severe drawback for curved energetic domains with a still noticable effect for surface energies. A geometrically nonlinear buckling model is proposed based on linear elastic material model. It is implemented in an ordinary differential equations solver and the solutions were confirmed to meet the finite element method (FEM) results to a very high degree. The theory is integrated with surface layers in which its accuracy was confirmed when compared with FEM results.Item Open Access Tight binding modeling of two dimensional and quasi-two dimensional materials(Bilkent University, 2017-09) Singh, Deepak KumarSince the advent of graphene, two-dimensional (2D) materials have consistently been studied owing to their exceptional electronic and optical properties. While graphene is completely two-dimensional in nature, its other analogues from the group IV A elements in the periodic table have been proven to have a low-buckled structure which adds up the exotic properties exhibited by them. The semiconductor industry is striving for such materials exhibiting exotic electronic, optical and mechanical properties. In this thesis work we are primarily working towards a generalized tightbinding (TB) model for the 2D family of group IV A elements. Graphene has been studied extensively and we have successfully reproduced its energy bandstructure accounting up to the third nearest neighbor contributions. The results have been checked extensively by performing simulations over a large set of available parameters and are found to be accurate. The other graphene analogues (viz; silicene, germanene and stanene) exhibiting a hexagonal 2D structure have been reported to have a buckling associated to them. We have analytically built up a TB model by considering the orbital projections along the bond length which accounts for the buckling in these 2D structures. Electronic band-structures have been reproduced and compared by taking into account the nearest neighbor and next-nearest neighbor contributions. Since these structures exhibit a Dirac like cone at the Dirac point and showing linear dispersion, study of electronic bandstructures in detail becomes indispensable. After the famous Kane and Mele paper on Quantum Spin Hall E ect in Graphene, condensed matter physicists have been looking for similar phenomena in other 2D materials. We have successfully included the spin-orbit coupling (SOC) contribution to our unperturbed Hamiltonian and were able to produce splitting around the Dirac points. Since, Silicene and its other analogues exhibit same structure with di erent amount of buckling, we were able to track down the whole energy band-structure. Alongside this thesis also focuses on calculating optical properties of these materials. In essence, this thesis work is an insight to the electronic and optical properties of the hexagonal 2D structures from the carbon family group. Derived structures from these 2D materials (viz; quantum dot, nano ribbon) could easily be studied utilizing the tight-binding formulation presented here. The proposed future work is the inclusion of nitrides and transition metal dichalcogenides (TMDCs) in the TB model.Item Open Access A unifying approach towards the geometrical instabilities of compressible, multilayer domains(Bilkent University, 2022-07) Bakiler, Ayşe DeryaInstabilities that arise in layered systems have been a riveting course of study for the past few decades, having found utility in various fields, while also being frequently observed in biological systems. However, the large deformation bifurcation analysis of compressible domains remains vastly understudied compared to the incompressible case. In this work, we present a unifying approach for the instability analysis of multilayer compressible elastic domains under plane deformations, also extending the approach to include the general interface model and to capture growth-induced instabilities. First, a linear elastic, displacement-based approach to capture bilayer wrinkling is taken, outlining the basics of such an approach. Then, the large-deformation incremental analysis for a rectangular, compressible, hyperelastic domain under plane deformations is developed, which serves as a generic framework for other geometries. This framework is applied to beam, half-space, bilayer and trilayer structures. Next, the framework is extended to account for the general interface model, looking into coated half-spaces, coated beams, and bilayers with interfaces. Finally, the framework is derived to account for both compression and growth. Obtained analytical results for the onset of wrinkling are compared with computational simulations using the finite element method (FEM) enhanced with eigenvalue analysis, cultivating excellent agreements between analytical and numerical results all across the material and geometrical parameter spectrum, and portraying clearly the significant effect of compressibility on bifurcation behavior. The analytical framework presented here provides grounds for further works on other modes of instabilities and more complex geometries.