Nanoelectromechanical Systems Devices Research Articles

A Hybrid Orbitrap-Nanoelectromechanical Systems Approach for the Analysis of Individual, Intact Proteins in Real Time.

Nanoelectromechanical systems (NEMS)-based mass spectrometry (MS) is an emerging technique that enables determination of the mass of individual adsorbed particles by driving nanomechanical devices at resonance and monitoring the real-time changes in their resonance frequencies induced by each single molecule adsorption event. We incorporate NEMS into an Orbitrap mass spectrometer and report our progress towards leveraging the single-molecule capabilities of the NEMS to enhance the dynamic range of conventional MS instrumentation and to offer new capabilities for performing deep proteomic analysis of clinically relevant samples. We use the hybrid instrument to deliver E. coli GroEL molecules (801 kDa) to the NEMS devices in their native, intact state. Custom ion optics are used to focus the beam down to 40 μm diameter with a maximum flux of 25 molecules/second. The mass spectrum obtained with NEMS-MS shows good agreement with the known mass of GroEL.

Advanced Computer Vision and AI Techniques for Nano-Scale Quality Control in Aerospace Manufacturing

This paper examines the integration of advanced computer vision (CV) techniques and Artificial Intelligence (AI) algorithms to improve quality control (QC) for nano-scale manufacturing processes in the space industry. As nanotechnology is regularly used in the space industry for manufacturing electromechanical components such as NEMS (Nanoelectromechanical Systems), solar panels, and energy storage devices, it's becoming increasingly important to detect defects or imperfections in one of those systems to prevent the loss of life and a costly catastrophe. In order to help mediate this issue, this paper will discuss the methods and processes that can be implemented to capture and analyze nano-scale images and data in order to detect possible flaws in the components.

Dynamic behaviors of delaminated nanofilms partly bonded on substrates with sub-nanoscale van der Waals dynamic boundaries

Abstract Dynamic buckling-induced delamination of nanofilms on substrates is a universal and essential phenomenon in nanoelectromechanical systems (NEMS). Van der Waals (vdWs) interactions play an important role in the dynamic buckling-induced delamination of nanofilms on substrates due to the interaction distances at nanoscale or even sub-nanoscale in NEMS. Therefore, it is interesting yet challenging to reveal the effect of intermolecular vdWs interactions on dynamic buckling-induced delamination of nanofilms on substrates. By considering sub-nanoscale dynamic boundary effects induced by intermolecular vdWs interactions, a parametric excitation nonlinear vibration model for dynamic buckling-induced delamination of nanofilms partly bonded on substrates is established. Effects of sub-nanoscale vdWs dynamic boundaries on transient and steady-state responses of dynamically delaminated nanofilms on substrates are analyzed. The sub-nanoscale vdWs dynamic boundaries lead the dynamic responses of delaminated-nanofilm/substrate systems very sensitive to initial conditions. The bending and shifting frequency response results demonstrated that the system nonlinearities can be greatly amplified by the sub-nanoscale vdWs dynamic boundary effect. Moreover, the spontaneous symmetry breaking and violent interfacial tearing/healing phenomena can be also triggered in the systems. Based on spontaneous symmetry breaking, a trans-scale relationship between nanofilm equilibrium positions and intermolecular vdWs interactions is established, which can provide a promising route for trans-scale measurements of molecular scale interfacial interactions. The work can also be helpful for the dynamic design of resonant NEMS devices based on nanofilm/substrate systems.

Thermocapillary oscillations in liquid thin films: Interplay of substrate topography and thermal wave

Liquid flows over patterned and/or contoured substrates is utilized in many practical applications e.g., lubrication flow in MEMS (micro-electromechanical systems) /NEMS (nano-electromechanical systems) devices, cell sorting operations in biology, etc. The topological gradients in such geometries induce thermal gradients, which in turn generates Marangoni hydrodynamics. Here, we theoretically showcase the interplay of substrate topology, imposed wavy temperature stimulus, and chemically patterned wall slip to generate thermo-capillarity in thin liquid films. We obtain analytical solutions for the thermal and the hydrodynamic fields for low Marangoni Ma and Reynolds Re number thermocapillary effect. Vorticity is observed to generate and transport at the liquid-gas interface, and further transported to the bulk film by vertical diffusion and convection. We also study further to understand the significance of different geometric and physical parameters on the Marangoni thermo-fluid-dynamics. Interplay of constructive and destructive interference between the wave forms of the substrate topology and imposed periodic thermal stimulus may yield maximum interfacial temperature gradients and strong thermo-capillarity. It is also observed that the lower values of system Biot number Bi enables better diffusion of heat from the patterned substrate to obtain stable thermo-capillarity. Further, the presence of optimal slip patterning allows for stronger and tuned circulations in the liquid film.

Vibration analysis of nanobeams subjected to gradient-type heating due to a static magnetic field under the theory of nonlocal elasticity

Nanoelectromechanical systems (NEMS) have received great interest from researchers around the world since the advent of nanotechnology and nanoengineering. This can be attributed due to the unique characteristics of NEMS devices and their wide range of applications. Among these applications, nanobeams and nanotubes now have an important role in the design of a variety of NEMS engineering devices. In the current research, the thermoelastic vibration analysis of Euler–Bernoulli nanobeams has been investigated using the theory of non-local elasticity proposed by Eringen. Also to study the effect of temperature change, the generalized thermoelastic model with dual phase-lag (DPL) is applied. The studied nanobeam is subjected to an axial thermal excitation load and surrounded by a magnetic field of constant strength. The Laplace transform technique has been used to solve the system differential equations and to find an approximate analytical solution for the different physical fields of the nanobeam. The numerical results obtained for the studied variables have been graphically clarified and discussed analytically. The effects of various influencing factors such as magnetic field strength, temperature change, non-local parameter as well as ramp type parameter have been examined and studied in detail.

Size-dependent mechanical properties of twin graphene

Twin Graphene, a novel 2D planar semiconducting carbon allotrope predicted recently, has attracted tremendous attention due to its potential applications in nano electromechanical systems (NEMS). In this paper, we use Molecular Dynamics simulations to investigate the mechanical properties of twin graphene. By performing uniaxial tensile loading, we find that the Young’s modulus, failure stress and fracture strain of a twin graphene sheet are strongly dependent on its size. Rectangular sheets show more apparent anisotropy of mechanical properties than square sheets. Our results also demonstrate that the fracture pattern of twin graphene is dependent on its geometry, as a result of its diverse bond types and orientations. These findings present an in-depth understanding of size dependent mechanical properties of twin graphene, and may benefit its future applications as building blocks of NEMS devices.

Static and dynamic characteristics of electrostatically actuated graphene bridge resonator

Graphene emerges as an important class of material for Nanoelectromechanical System (NEMS) because of their exceptional mechanical properties. We have systematically investigated static and dynamic characteristics of an electrostatically actuated graphene bridge resonator. The graphene bridge resonator has been modelled in finite element software as a 3D device. We have analysed the effect of internal stress and electrostatic actuation force on static and dynamic characteristics of the graphene bridge resonator. Internal stress can be built-up in the graphene sheet due to variation in operating temperature of a NEMS device. We have also investigated the effect of variation of size and nature of end boundary conditions on the static and dynamic characteristics of the electrostatically actuated graphene bridge resonators. It has been found that the natural frequencies of bridge resonator can be considerably tuned by variation of electrostatic actuation force and internal stress. We have also observed that the choice of boundary conditions has a significant role in characterization of graphene bridge resonators.

Formation of wavy carbon nanofibers and nanocoils via precursor constrained microbuckling

Flexible carbon nanosprings and wavy nanofibers can be used in micro and nanoelectromechanical system devices, deployable structures, flexible displays, energy storage, catalysis, nanocomposites and a multitude of other uses. A novel method to produce wavy and helical carbon nanofibers (CNFs) is presented here. The CNFs with controlled geometry were fabricated via pyrolysis of electrospun polyacrylonitrile (PAN) nanofibers as the precursor. The waviness/helicity of nanofibers was achieved by subjecting the precursor nanofibers to constraint buckling inside a thermally shrinking matrix. The much higher tendency of the matrix to shrink, compared to PAN nanofibers, was achieved by controlling the microstructure and crystallinity of the precursors. The formation of the wavy/helical geometry was explained quantitatively via mechanistic models, by minimizing the total mechanical energy stored in the PAN-matrix system during the matrix shrinkage. Despite its simplicity in considering elastic deformations only, the model provided reasonably quantitative matching with the experiments. Compared to existing methods in generating wavy/helical nanofibers, such as chemical vapor deposition growth methods, our method provides a more controllable geometry which is suitable for large scale production of aligned buckled CNFs.

Graphene ribbons with suspended masses as transducers in ultra-small nanoelectromechanical accelerometers

Nanoelectromechanical system (NEMS) sensors and actuators could be of use in the development of next generation mobile, wearable, and implantable devices. However, these NEMS devices require transducers that are ultra-small, sensitive and can be fabricated at low cost. Here, we show that suspended double-layer graphene ribbons with attached silicon proof masses can be used as combined spring-mass and piezoresistive transducers. The transducers, which are realized using processes that are compatible with large-scale semiconductor manufacturing technologies, can yield NEMS accelerometers that occupy at least two orders of magnitude smaller die area than conventional state-of-the-art silicon accelerometers.

Size-dependent resonant response of a double-layered viscoelastic nanoresonator under electrostatic and piezoelectric actuations incorporating surface effects and Casimir regime

Nonlinear dynamics of a double-layer viscoelastic nanobeam embedded into an electromechanical system is investigated in this paper. The nanoelectromechanical system (NEMS) consists of two piezoelectric and Kelvin–Voigt viscoelastic nanobeams with visco-Pasternak medium in between. An electrostatic force which is the combination of DC and AC voltages is applied to the lower nanobeam through the fixed electrode. Taking into account both the small-scale effect and surface energy effect, the modified couple-stress theory together with Gurtin–Murdoch elasticity theory is implemented. As intermolecular interactions between the fixed and lower electrodes, the influence of Casimir regime on the dynamic behavior of the NEMS device is also included in the proposed model. The differential motion’s equations are derived by means of Hamilton’s principle and discretized to a set of nonlinear ODEs through Galerkin’s decomposition procedure. In order to capture the steady-state dynamic response of the system, a combined shooting and arclength continuation method is schemed. A comprehensive study has been carried out on the impact of viscoelasticity, size-dependency, surface effects, direct and alternating current voltages, piezoelectric voltage and visco-Pasternak parameters on the frequency-response behavior of the system near primary resonance. Furthermore, some bifurcation points in the frequency-response curves are addressed. The combined hardening–softening-type behaviors are observed in the dynamic response of the system. It has been shown that the nonlinear characteristics of the motion of the proposed NEMS device have sensitive-dependence on some of the mentioned parameters.

Effects of Size, Surface Energy and Casimir Force on the Superharmonic Resonance Characteristics of a Double-Layered Viscoelastic NEMS Device Under Piezoelectric Actuations

This paper investigates the nonlinear characteristics of a double-layered viscoelastic nanoelectromechanical system (NEMS) in the vicinity of superharmonic resonance. Two nanobeams are made of piezoelectric material and coupled through a visco-Pasternak medium in between. Modified couple-stress theory together with Gurtin–Murdoch surface elasticity theory is utilized to take into account the effects of size-dependency and surface energy for the nanosized structure. Kelvin–Voigt model is also implemented to consider the impact of viscoelasticity. The differential equations of motion are established based on Hamilton’s principle and decomposed to a set of nonlinear ordinary differential equations via Galerkin discretization method. Arclength continuation technique is schemed to capture the frequency–response curves near superharmonic resonance of the system. The influence of the couple-stress parameter, surface strain energy and dispersion force on the nonlinear behavior of the system near superharmonic resonance has been studied. It is observed, that the hardening and softening behaviors of the system are remarkably affected by the size and surface parameters, and interatomic Casimir force. Finally, considering all the mentioned effects, the influence of the DC and AC voltage loads on the dynamic pull-in behavior of the NEMS device is investigated. For these cases, some frequency ranges are addressed as the pull-in band in which the lower nanobeam collapses.

Dynamical response of multi-walled carbon nanotube resonators based on continuum mechanics modeling for mass sensing applications

Carbon nanotube (CNT) has recently received much attention due to its excellent electromechanical properties, indicating that CNT can be employed for development of Nanoelectromechanical system (NEMS) such as nanomechanical resonators. For effective design of CNT-based resonators, it is required to accurately predict the vibration behavior of CNT resonators as well as their frequency response to mass adsorption. In this work, we have studied the vibrational behavior of Multi-walled CNT (MWCNT) resonators by using a continuum mechanics modeling that was implemented in Finite element method (FEM). In particular, we consider a transversely isotropic hollow cylinder solid model with Finite element (FE) implementation for modeling the vibration behavior of Multi-walled CNT (MWCNT) resonators. It is shown that our continuum mechanics model provides the resonant frequencies of various MWCNTs being comparable to those obtained from experiments. Moreover, we have investigated the frequency response of MWCNT resonators to mass adsorption by using our continuum model with FE implementation. Our study sheds light on our continuum mechanics model that is useful in predicting not only the vibration behavior of MWCNT resonators but also their sensing performance for further effective design of MWCNT-based NEMS devices.

Application of the variational iteration method to nonlinear vibrations of nanobeams induced by the van der Waals force under different boundary conditions

The pull-in instability is one of the most important phenomena which is usually associated with nanobeams when they are used in nanoelectromechanical systems (NEMS). This phenomenon may occur without electrical excitation and depends on different parameters. The aim of this paper is to investigate the nonlinear vibrations and pull-in instability of nanobeams in the presence of the van der Waals (vdW) force without electrical excitation. Utilizing Galerkin's method, the partial differential equation of motion is transferred to a nonlinear ordinary differential equation. Afterwards, the variational iteration method (VIM) is employed to obtain the nonlinear frequency and deflection of the nanobeam. The study is performed on doubly clamped, doubly simply supported and clamped-simply supported boundary conditions. The effects of boundary conditions, axial load, aspect ratio and the vdW force on nonlinear frequency and deflection as well as pull-in instability are discussed in details. In addition, three simple and useful equations are developed for predicting the critical values of the vdW force parameter in terms of axial load and aspect ratio parameters. These equations can be employed to estimate the dimensions of nanobeams before their fabrication and using them in the NEMS devices.

Probing the chaotic boundary of a membrane resonator with nanowire arrays

Mechanically induced nonlinearities in nano-electromechanical systems (NEMSs) are typically avoided in design due to their unpredictable nature; however, by incorporating these normally unwanted nonlinear and chaotic phenomena, the performance of NEMS devices displays substantially different characteristics opening a broad new range of potential applications for their use. In this work, experiments have been conducted for probing the chaotic boundary of a circular membrane mechanical resonator with and without a silicone nanowire array (Si NWA). The NWA resonator can transition from linear to nonlinear quasi-periodic behaviour, and further transition into a chaotic state at resonance. Moreover, the NWA resonator demonstrated a high level of complex nonlinear behaviours, as the device expands the power spectral response from a single frequency at a linear regime to a wideband continuous frequency spectrum when chaotic behaviour was initiated; the threshold power of this transition decreased with a smaller NWA diameter. It was also observed that the NWA resonator had higher damping compared to the resonator without a NWA; however, as the vibration velocity of the NWA resonator increased, complex air damping and thin squeeze film damping lowered the threshold for probing the chaotic boundary condition of the NWA resonator.

Graphene transfer methods for the fabrication of membrane-based NEMS devices

Graphene has extraordinary mechanical and electronic properties, making it a promising material for membrane based nanoelectromechanical systems (NEMS). Here, three methods for direct transfer of chemical vapor deposited graphene onto pre-fabricated micro cavity substrates were investigated and analyzed with respect to yield and quality of the free-standing membranes on a large-scale. An effective transfer method for layer-by-layer stacking of graphene was developed to improve the membrane stability and thereby increase the yield of completely covered and sealed cavities. The transfer method with the highest yield was used to fabricate graphene NEMS devices. Electrical measurements were carried out to successfully demonstrate pressure sensing as a possible application for these graphene membranes.

(Invited) Plasma Processes for Emerging Silicon-Based MEMS, NEMS and Packaging Applications

Plasma processes are important for emerging silicon-based micro-electro-mechanical systems (MEMS), nano-electro-mechanical systems (NEMS) and packaging applications. Typically every device has a customised process flow but synergies can be found as most are produced using a 2.5D approach comprising sequential deposition, lithography and etch cycles. Plasma processes are critical in enabling reproducible dry deposition and etch steps during the manufacturing flow of MEMS and NEMS devices but individual tools need the flexibility to address multiple different applications and process requirements. Increasingly plasma processes are also being adopted in nano-imprint lithography and bonding process steps. Plasma processes may be divided into the following broad families: chemical vapour deposition (CVD), atomic layer deposition (ALD), physical vapour deposition (PVD), surface functionalisation, etch (physically-driven) and etch (chemically-driven). The merits of each plasma technique and their application to emerging devices are discussed – including silicon etch processes that are at the heart of most MEMS and NEMS devices. Here trends are towards higher aspect ratios for enhanced performance and smaller footprint whilst maintaining throughput. Increasingly, large cavities are also being etched to realise membrane-based devices and in multi-wafer stacks where through silicon vias (TSVs) are emerging as a key technology for interconnect. At the research stage, the integration of ALD into MEMS is becoming more common whilst in NEMS devices are taking advantage novel combinations of processes and materials to realise new functions.

Free vibration of wavy single-walled fluid-conveying carbon nanotubes in multi-physics fields

Fluid-conveying carbon nanotubes (CNTs) have attracted much attention and they are used in nano-electromechanical systems (NEMS). In this study, we investigate the free vibration of embedded single-walled fluid-conveying carbon nanotubes in magnetic and temperature fields. The CNTs are modeled as wavy Timoshenko beams. Based on the nonlocal beam theory, the governing equations of motion are derived using Hamilton’s principle. These equations are solved using the Galerkin approach, thereby obtaining a set of ordinary differential equations from the partial differential equations of motion. Numerical examples are analyzed to determine the differences between the proposed model and some previously reported models, as well as the effects of the nonlocal parameter, the fluid velocity and density, the temperature and magnetic field flux change, and the surrounding elastic medium on the dynamic behavior of wavy CNTs. The numerical results validate the proposed analytical model, thereby allowing us to conclude that this method may facilitate the application of fluid-conveying CNTs as NEMS devices.

Motional entanglement with trapped ions and a nanomechanical resonator

We study the entangling power of a nanoelectromechanical system (NEMS) simultaneously interacting with two separately trapped ions. To highlight this entangling capability, we consider a special regime where the ion-ion coupling does not generate entanglement in the system, and any resulting entanglement will be the result of the NEMS acting as an entangling device. We study the dynamical behavior of the bipartite NEMS-induced ion-ion entanglement as well as the tripartite entanglement of the whole system (ions+NEMS). We found some quite remarkable phenomena in this hybrid system. For instance, the two trapped ions initially uncorrelated and prepared in coherent states can become entangled by interacting with a nanoelectromechanical resonator (also prepared in a coherent state) as soon as the ion-NEMS coupling achieve a certain value, and this can be controlled by external voltage gate on the NEMS device.

Understanding of Initial Unstable Contact Behaviors of Au-to-Au Microcontact under Low Contact Force for Micro- and Nano-Electromechanical System Devices

The Au-to-Au micro/nano-contact behavior in unstable contact region during the initial stage of contact formation has been experimentally investigated under low contact force. The experimental results reveal that the asperity deformation process, which is conventionally observed in the stable region, could start from the early stage of contact formation in the unstable region. The fundamental mechanism for the instability of electrical conductance in the unstable region can be explained under a framework of trap-assisted tunneling at the contact interface.

A continuum model for the static pull-in behavior of graphene nanoribbon electrostatic actuators with interlayer shear and surface energy effects

Based on multi-beam shear model theory, a continuum mechanics model is developed to investigate the pull-in instability of wedged/curved multilayer graphene nanoribbon (MLGNR) cantilever nanobeams subjected to electrostatic and Casimir forces. The first-order fringing-field correction, the interlayer shear between neighboring graphene nanoribbons (GNRs), surface elasticity, and residual surface tension are incorporated into the analytical model. An explicit closed-form analytical solution to the governing fourth-order nonlinear differential equation of variable coefficients is introduced for the static pull-in behavior of electrostatic nanoactuators using a Fredholm integral equation of the first kind. A comparison study for a [001] silver electrostatic nanoactuator indicates that the proposed analytical closed-form solution yields an improved accuracy over other analytical and numerical methods existing in literature. The results indicate that the interfacial slip between GNRs and the surface material parameters play a significant role in static pull-in behavior of MLGNR electrostatic nanoactuators. From the experimental data and atomistic simulations available in the literature, the value of interlayer shear modulus at the graphene/graphene interface is estimated to be in the order of magnitude of 10−1 GPa. The continuum model proposed in this study will be helpful for characterizing the mechanical properties of GNRs and the design of graphene-based nanoelectromechanical system devices.