Flat Cantilever Research Articles

Two-layer elastic models for single-yeast compressibility with flat microlevers.

Unicellular organisms such as yeast can survive in very different environments, thanks to a polysaccharide wall that reinforces their extracellular membrane. This wall is not a static structure, as it is expected to be dynamically remodeled according to growth stage, division cycle, environmental osmotic pressure and ageing. It is therefore of great interest to study the mechanics of these organisms, but they are more difficult to study than other mammalian cells, in particular because of their small size (radius of a few microns) and their lack of an adhesion machinery. Using flat cantilevers, we perform compression experiments on single yeast cells (S. cerevisiae) on poly-L-lysine-coated grooved glass plates, in the limit of small deformation using an atomic force microscope (AFM). Thanks to a careful decomposition of force-displacement curves, we extract local scaling exponents that highlight the non-stationary characteristic of the yeast behavior upon compression. Our multi-scale nonlinear analysis of the AFM force-displacement curves provides evidence for non-stationary scaling laws. We propose to model these phenomena based on a two-component elastic system, where each layer follows a different scaling law..

Triaxial tactile sensor utilizing standing laser-induced graphene cantilevers on polyimide film

Microelectromechanical systems (MEMS) multiaxial tactile sensors have been developed in various fields to leverage their small size, high accuracy, and high sensitivity. Although various measurement principles have been proposed, most tactile sensors are fabricated using conventional and complicated Si processes. Conversely, laser-induced graphene (LIG) has recently attracted significant attention as a material for fabricating physical sensors due to its high sensitivity as a piezoresistor through simple laser processing. Therefore, the application of LIG to MEMS processes is expected to yield unprecedented MEMS sensor devices. In this paper, we propose a triaxial tactile sensor using standing LIG cantilevers embedded in an elastic body. The proposed sensing element was fabricated using ultraviolet (UV) laser irradiation to shape a polyimide film into cantilever structures and CO2 laser irradiation to form LIG strain gauges. Subsequently, the flat LIG cantilevers were stood up using thermal deformation. These multiple three-dimensional LIG cantilever elements enable multiaxial force measurements. The cantilever and elastic body portion of the sensor had dimensions of 3 × 3 × 0.2 mm and 12.5 × 12.5 × 3 mm, respectively. The fabricated sensor response was evaluated, and its capability to independently measure triaxial forces was verified. Therefore, the proposed simple and reproducible fabrication process is useful for realizing compact multiaxial tactile sensors.

A Review of Piezoelectric Footwear Energy Harvesters: Principles, Methods, and Applications.

Over the last couple of decades, numerous piezoelectric footwear energy harvesters (PFEHs) have been reported in the literature. This paper reviews the principles, methods, and applications of PFEH technologies. First, the popular piezoelectric materials used and their properties for PEEHs are summarized. Then, the force interaction with the ground and dynamic energy distribution on the footprint as well as accelerations are analyzed and summarized to provide the baseline, constraints, potential, and limitations for PFEH design. Furthermore, the energy flow from human walking to the usable energy by the PFEHs and the methods to improve the energy conversion efficiency are presented. The energy flow is divided into four processing steps: (i) how to capture mechanical energy into a deformed footwear, (ii) how to transfer the elastic energy from a deformed shoes into piezoelectric material, (iii) how to convert elastic deformation energy of piezoelectric materials to electrical energy in the piezoelectric structure, and (iv) how to deliver the generated electric energy in piezoelectric structure to external resistive loads or electrical circuits. Moreover, the major PFEH structures and working mechanisms on how the PFEHs capture mechanical energy and convert to electrical energy from human walking are summarized. Those piezoelectric structures for capturing mechanical energy from human walking are also reviewed and classified into four categories: flat plate, curved, cantilever, and flextensional structures. The fundamentals of piezoelectric energy harvesters, the configurations and mechanisms of the PFEHs, as well as the generated power, etc., are discussed and compared. The advantages and disadvantages of typical PFEHs are addressed. The power outputs of PFEHs vary in ranging from nanowatts to tens of milliwatts. Finally, applications and future perspectives are summarized and discussed.

Nonlinear restructuring of patterned thin films by residual stress engineering into out-of-plane wavy-shaped electrostatic microactuators for high-performance radio-frequency switches

Electrostatic microelectromechanical (MEMS) switches are the basic building blocks for various radio-frequency (RF) transceivers. However, conventional cantilever-based designs of MEMS switches require a large actuation voltage, exhibit limited RF performance, and suffer from many performance tradeoffs due to their flat geometries restricted in two dimensions (2D). Here, by leveraging the residual stress in thin films, we report a novel development of three-dimensional (3D) wavy microstructures, which offer the potential to serve as high-performance RF switches. Relying on standard IC-compatible metallic materials, we devise a simple fabrication process to repeatedly manufacture out-of-plane wavy beams with controllable bending profiles and yields reaching 100%. We then demonstrate the utility of such metallic wavy beams as RF switches achieving both extremely low actuation voltage and improved RF performance owing to their unique geometry, which is tunable in three dimensions and exceeds the capabilities of current state-of-the-art flat-cantilever switches with 2D-restricted topology. As such, the wavy cantilever switch presented in this work actuates at voltages as low as 24 V while simultaneously exhibiting RF isolation and insertion loss of 20 dB and 0.75 dB, respectively, for frequencies up to 40 GHz. Wavy switch designs with 3D geometries break through the design limits set by traditional flat cantilevers and provide an additional degree of freedom or control knob in the switch design process, which could enable further optimization of switching networks used in current 5G and upcoming 6G communication scenarios.

THE PROBLEM OF CRACK OPENING WIDTH AND STIFFNESS OF REINFORCED CONCRETE STRUCTURES, BUILDINGS AND CONSTRUCTIONS

The article defines the main results for the development of reinforced concrete mechanics. In the isotropic medium between the cracks is used "first object - flows-blocks", "second object - main cracks" and the effect of reinforced concrete, the physical essence of which is the non-uniformity of concrete and continuous reinforcement. Reactions arise in the concrete for deformation of the reinforcement from the bonding of the compressed concrete in the tensile region. The average resistance of the tensile concrete and the "average total force of the working reinforcement," the third object, are transmitted through the effect of reinforced concrete and the "dowel" effect. The crack opening widths are the relative mutual displacements of reinforcement and concrete, determined from the boundary conditions and the Thomas-Author hypothesis. A new classification of cracks has been developed: regular cracks (anisotropic medium of reinforced concrete) and main cracks based on the effect of reinforced concrete (origins - concentrations) and maximum opening in the closed equations of mechanics of reinforced concrete from the Lagrange function. The author has proposed hypotheses, theorems of linear and angular deformations, functionals for deplanation of cross section of reinforced concrete element from elastic-plastic stage, jumps - cracks and stiffness matrix in a single compound strip which allow to reduce the order of differential equations. The resistance design model method for reinforced concrete mechanics is used for the rod, wall, and slab of the "envelope" of cracks. Hybrid from Lira (finite element method of reinforced concrete from anisotropy) developed in the form of two finite element effect of reinforced concrete of "flat and spatial cantilever" for external and internal displacements. The general principle from Loleith to the "opening - closing" of cracks, the stiffness of the mechanics of reinforced concrete is obtained in the form of the method of the computational model of resistance.

A Flexible Flow Sensor for Detecting Airflow Velocity and Incident Angle

A flexible flow sensor is proposed to measure the airflow velocity and incident angle. The sensor consists of a polyimide (PI) substrate, a flat cantilever beam and a graphene piezoresistor. The cantilever beam deforms under the action of fluid-structure interaction (FSI), resulting in changes in the resistance of the graphene piezoresistor. The piezoresistor was prepared by spraying coating of graphene inks using a patterned parylene mask and then encapsulated by coating another polyimide layer to form a sandwiched structure. Experimental results indicate that the flow sensor has a wide detection range of flow velocity (0-30 m/s) and incident angle (0-25°), with a high resolution of 0.94 m/s and 0.23°, respectively. Compared with curved cantilever, the flat cantilever achieves higher sensitivity to the incident angle, and smaller disturbance to the flow field. The arrangement of the flow sensors on an airfoil is discussed for estimation of flight parameters.

Design of Microfabricated Mechanically Interlocking Metamaterials for Reworkable Heterogeneous Integration

Abstract Next-generation interconnects utilizing mechanically interlocking structures enable permanent and reworkable joints between micro-electronic devices. Mechanical metamaterials, specifically dry adhesives, are an active area of research which allows for the joining of objects without traditional fasteners or adhesives, and in the case of chip integration, without solder. This paper focuses on reworkable joints that enable chips to be removed from their substrates to support reusable device prototyping and packaging, creating the possibility for eventual pick-and-place mechanical bonding of chips with no additional bonding steps required. Analytical models are presented and are verified through finite element analysis (FEA) assuming pure elastic behavior. Sliding contact conditions in FEA simplify consideration of several design variations but contribute ∼10% uncertainty relative to experiment, analysis, and point-loaded FEA. Two designs are presented; arrays of flat cantilevers have a bond strength of 6.3 kPa, and nonflat cantilevers have a strength of 29 kPa. Interlocking designs present self-aligning in-plane forces that emerge from translational perturbation from perfect alignment. Stresses exceeding the material yield stress during adhesion operations present a greater concern for repeatable operation of compliant interlocking joints and will require further study quantifying and accommodating plastic deformation. Designs joining a rigid array with a complementary compliant cantilever array preserve the condition of reworkability for the surface presenting the rigid array. Eventual realization of interconnect technology based on this study will provide a great improvement of functionality and adaptability in heterogeneous integration and microdevice packaging.

Measuring the Casimir Forces with an Adhered Cantilever: Analysis of Roughness and Background Effects

Technological progress has made possible precise measurements of the Casimir forces at distances less than 100 nm. It has enabled stronger constraints on the non-Newtonian forces at short separations and improved control of micromechanical devices. Experimental information on the forces below 30 nm is sparse and not precise due to pull-in instability and surface roughness. Recently, a method of adhered cantilever was proposed to measure the forces at small distances, which does not suffer from the pull-in instability. Deviation of the cantilever from a classic shape carries information on the forces acting nearby the adhered end. We calculate the force between a flat cantilever and rough Au plate and demonstrate that the effect of roughness dominates when the bodies approach the contact. Short-distance repulsion operating at the contact is included in the analysis. Deviations from the classic shape due to residual stress, inhomogeneous thickness of the cantilever, and finite compliance of the substrate are analysed. It is found that a realistic residual stress gives a negligible contribution to the shape, while the finite compliance and inhomogeneous thickness give measurable contributions that have to be subtracted from the raw data.

Evaluating Young's Modulus of Single Yeast Cells Based on Compression Using an Atomic Force Microscope with a Flat Tip.

In this research, atomic force microscopy (AFM) with a flat tip cantilever is utilized to measure Young's modulus of a whole yeast cell (Saccharomyces cerevisiae BY4741). The results acquired from AFM are similar to those obtained using a microfluidic chip compression system. The mechanical properties of single yeast cells are important parameters which can be examined using AFM. Conventional studies apply AFM with a sharp cantilever tip to indent the cell and measure the force-indentation curve, from which Young's modulus can be calculated. However, sharp tips introduce problems because the shape variation can lead to a different result and cannot represent the stiffness of the whole cell. It can lead to a lack of broader meaning when evaluating Young's modulus of yeast cells. In this report, we confirm the differences in results obtained when measuring the compression of a poly(dimethylsiloxane) bead using a commercial sharp tip versus a unique flat tip. The flat tip effectively avoids tip-derived errors, so we use this method to compress whole yeast cells and generate a force–deformation curve. We believe our proposed method is effective for evaluating Young's modulus of whole yeast cells.

Distributed Dynamic Load Identification on Irregular Planar Structures Using Subregion Interpolation

Spatially distributed load on aircraft structures is difficult to obtain due to the limitation of measurement technology, the complexity of load and the external environment of the aircraft during flight, etc. A load identification method based on a subregion interpolation technique is proposed to indirectly estimate the distributed dynamic load from measured strain data on planar structures. The load distribution area is discretized into several subregions and the load distribution function in each subregion is represented by a set of local interpolation functions multiplied by their corresponding coefficients. A modified Green’s function matrix is formulated to establish the relationship between the local distributed dynamic load in the domain composed of the subregions sharing the same node and the structural response data. Hence, both the load’s distribution and time histories can be identified from structural response by solving the new formulated inverse problem. Numerical simulations on a flat cantilever plate and a planar structure with irregular geometry are conducted to show the effectiveness of the proposed method. Results show that the proposed method has better adaptability on the types of load distribution and structural configurations than the existing methods.

The effects of flexible vortex generator on the wake structures for improving turbulence

Turbulence is a very useful flow characteristic that is used in many engineering devices to facilitate mixing, heat transfer in heat exchanger and improving aerodynamics in propeller. This paper has numerically studied the spatial characteristics of the wake behind a free-oscillating flexible vortex generator (FVG) in order to evaluate its turbulence generation ability. As the wake is playing as the effective turbulence region, the spatial characteristics can reflect the ability of the FVG in turbulence generation when a larger wake size indicates a greater turbulence region. Two VGs are considered in this study; circular and flat plate cantilever. Each VG was submerged individually in a subcritical flow (102 <ReD < 105) and the generated wake was studied. The wake behind the FVG was visualized via the lambda2 vortex identification criterion and it was compared with its respective rigid counterpart. From the comparison, it is found that the FVG has a larger wake compared to its rigid counterpart. The result demonstrates that the FVG can generate a larger turbulence region. The cause of the increasing wake size was found to be the weakening of downwash behind the FVG when it bends. The downwash becomes weaker as the deflection of the FVG increases.

Functionalization of Atomic Force Microscope Cantilevers with Single-T Cells or Single-Particle for Immunological Single-Cell Force Spectroscopy.

Atomic force microscopy based single cell force spectroscopy (AFM-SCFS) is a powerful tool for studying biophysical properties of living cells. This technique allows for probing interaction strengths and dynamics on a live cell membrane, including those between cells, receptor and ligands, and alongside many other variations. It also works as a mechanism to deliver a physical or biochemical stimulus on single cells in a spatiotemporally controlled manner, thus allowing specific cell activation and subsequent cellular events to be monitored in real-time when combined with live-cell fluorescence imaging. The key step in those AFM-SCFS measurements is AFM-cantilever functionalization, or in other words, attaching a subject of interest to the cantilever. Here, we present methods to modify AFM cantilevers with a single T cell and a single polystyrene bead respectively for immunological studies. The former involves a biocompatible glue that couples single T cells to the tip of a flat cantilever in a solution, while the latter relies on an epoxy glue for single bead adhesion in the air environment. Two immunological applications associated with each cantilever modification are provided as well. The methods described here can be easily adapted to different cell types and solid particles.

Cobalt-Iron-Manganese Electrodeposition for High Performance Magnetoelastic Resonators

Magnetostrictive Co-Fe-Mn films were investigated for their use in fabricating magnetoelastic resonators. Electrodepositing these films enables batch fabrication of resonators with varying geometries and therefore, resonant frequencies, while controlling the film stoichiometry and crystallography. Boron, phosphorous, and molybdenum were used to increase the electrical resistivity and control film texture. Additionally, ascorbic acid and TMAB were used as “oxygen scavengers” to control the chemistry’s stability and limit the oxidation of the Fe2+ to Fe3+. As suggested by Osaka et al, Fe(OH)3 is formed and included into the film resulting in a decrease of the saturation magnetic flux density (Bs) value as the Fe cation is oxidized[1,2]. Additives, such as Saccharin and Sorbitol, were added as grain refiners and stress reducers, enabling flat cantilever structures that did not bend out of plain due to intrinsic stress gradients. The composition and phase of the deposited films were controlled by temperature, agitation, concentrations in the electrodeposition chemistry, current density, and duty cycle of the pulsing regime. The samples were analyzed with EDS to determine the composition and XRD to look at film texture. Magnetic testing was performed using super conducting quantum interference device (SQUID) magnetometry, as well as visual inspection of the displacement on a deposit stress analyzer as a magnetic field was applied to the films. The magnetostriction was then correlated to EDS and XRD results to identify phase, stoichiometry and the plating parameters to produce improved magnetostriction while maintaining low intrinsic stress. Annealing studies of these films were performed using a tube furnace with inert gas to heat past the Curie temperature and then cool in the presence of an applied magnetic field. The applied magnetic field direction and its correlation with magnetic properties and phase will be discussed. Acknowledgement Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. References Osaka, T., et al., A high moment CoFe soft magnetic thin film prepared by electrodeposition. Electrochemical and Solid State Letters, 2003. 6(4): p. C53-C55.Elhalawaty, S., et al., Oxygen Incorporation into Electrodeposited CoFe Films: Consequences for Structure and Magnetic Properties. Journal of the Electrochemical Society, 2011. 158(11): p. D641-D646.

Evaluation of aerodynamic forces acting on oscillating cantilever beams based on the study of the damped flexural vibration of aluminium test samples

The paper is devoted to study of the aerodynamic forces acting on flat cantilever beams performing flexural vibrations in a viscous fluid. Original method for the force evaluation is presented based on analysis of experimental measurements of a logarithmic decrement of vibrations and relative variation in frequency of duralumin test specimens. The theoretical core of the method is based on the classical theory of bending beam oscillations and quasi-two dimensional model of interaction between a beam and a gas. Using the proposed method, extensive series of experiments for a wide range of oscillations parameters were carried out. The processing of the experimental data allowed to establish the global influence of the aerodynamic effects on beam oscillations and the local force characteristics of each cross-section of the beam in the form of universal functions of dimensionless amplitude and dimensionless frequency of oscillation. The obtained estimates of the drag and added mass forces showed a good correspondence with the available numerical and experimental data practically in the entire range of the investigated parameters.

Time Analysis of Building Dynamic Response Under Seismic Action. Part 2: Example of Calculation

The second part of the article illustrates the use of the time analysis method (TAM) by the example of the calculation of a 3-storey building, the design dynamic model (DDM) of which is adopted in the form of a flat vertical cantilever rod with 3 horizontal degrees of freedom associated with floor and coverage levels. The parameters of natural oscillations (frequencies and modes) and the results of the calculation of the elastic forced oscillations of the building’s DDM – oscillograms of the reaction parameters on the time interval t ∈ [0; 131,25] sec. The obtained results are analyzed on the basis of the computed values of the discrepancy of the DDS motion equation and the comparison of the results calculated on the basis of the numerical approach (FEM) and the normative method set out in SP 14.13330.2014 “Construction in Seismic Regions”. The data of the analysis testify to the accuracy of the construction of the computational model as well as the high accuracy of the results obtained. In conclusion, it is revealed that the use of the TAM will improve the strength of buildings and structures subject to seismic influences when designing them.

Note: A novel cantilever beam for low-frequency high performance piezoelectric geophone

A multilayer spiral-corrugated cantilever beam was developed as an improvement for a conventional single-layer flat cantilever beam to improve the performance of a piezoelectric geophone adopting polyvinylidene fluoride film for low frequency seismic vibration measurement. The proposed structure is longer and has less stiffness compared with the conventional beam, so the piezoelectric geophone adopting the developed cantilever beam has a lower natural frequency. To confirm the validity of the design, the finite element analysis was conducted and the results showed that the natural frequency of the geophone with the multilayer spiral-corrugated cantilever beam is much lower and the corrugated structure can improve the sensitivity of the geophone.

Durable adhesives based on electrospun poly(vinylidene fluoride) fibers

ABSTRACTHerein, the fabrication of poly(vinylidene fluoride) (PVDF) fibrous membrane using electrospinning is reported and its use for dry‐adhesive applications is demonstrated. The shear and normal adhesion performance of the samples was investigated using an Instron tensile tester and an atomic force microscope (AFM) respectively. For shear adhesion measurements, the electrospun membrane was finger pressed on to a glass slide and pulled in shear mode using a tensile tester. The thickness of the electrospun membrane was varied and the effect of thickness on shear adhesion was investigated. The shear adhesion strength increased when the thickness of the samples was reduced. Shear adhesion strength of a 200 µm thick sample was determined to be approximately 0.165 N/cm. For normal adhesion measurements, a flat tipless cantilever was used to indent the sample and then retract back to measure the pull‐off force. High shear adhesion strength and normal pull‐off force recorded are attributed to the fine size of the fibers that conform to the asperities present on the surfaces of the glass slide and the AFM cantilever. The durability of the adhesive was also verified by repeating the AFM adhesion measurements over 1000 consecutive attachment–detachment cycles. The pull‐off force was seen to be constant over 1000 attachment–detachment cycles. Our results indicate that these electrospun fibrous membranes can potentially be used as reusable dry‐adhesives. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44393.

Performance of pre-deformed flexible piezoelectric cantilever in energy harvesting

This paper proposes a novel structure for pre-rolled flexible piezoelectric cantilevers that use wind energy to power a submunition electrical device. Owing to the particular installation position and working environment, the submunition piezoelectric cantilever should be rolled when not working, but this pre-rolled state can alter the energy harvesting performance. Herein, a working principle and installation method for piezoelectric cantilevers used in submunitions are introduced. To study the influence of the pre-rolled state, pre-rolled piezoelectric cantilevers of different sizes were fabricated and their performances were studied using finite element analysis simulations and experiments. The simulation results show that the resonance frequency and stiffness of the pre-rolled structure is higher than that of a flat structure. Results show that, (1) for both the pre-rolled and flat cantilever, the peak voltage will increase with the wind speed. (2) The pre-rolled cantilever has a higher critical wind speed than the flat cantilever. (3) For identical wind speeds and cantilever sizes, the peak voltage of the flat cantilever (45 V) is less than that of the pre-rolled cantilever (56 V). (4) Using a full-bridge rectifier, the output of the pre-rolled cantilever can sufficiently supply a 10 μF capacitor, whose output voltage may be up to 23 V after 10 s. These results demonstrate that the pre-rolled piezoelectric cantilever and its installation position used in this work are more suitable for submunition, and its output sufficiently meets submunition requirements.

Modeling of machined surface quality in high-speed ball-end milling of Inconel-718 thin cantilevers

Machining of thin flexible parts in the aerospace and power industries often involves workpiece deflection majorly influencing the machined surface quality. Very few attempts have been done so far to address issues in the ball-end milling of thin cantilever-shaped parts made of “difficult-to-machine” materials. The objective of this paper is to optimize the machining parameters under the design constraints such as workpiece thickness, workpiece inclination, and cutter orientation to get the best possible machined surface quality. Accordingly, correlations between surface quality and the workpiece deflection have been developed. Independent variables were optimized using a central composite design (CCD) with each variable taken at five levels. All the results were compared with the results obtained by the ball-end milling on flat and horizontal cantilever without an inclination. Analytical models have been developed to predict the instantaneous workpiece deflection, undeformed chip thickness, and width of cut and correlated them with the machined surface quality. The lowest surface roughness of ~1 μm Ra was obtained at a higher cutting speed of 120 m/min and a lower feed rate of 400 mm/min, on thicker workpiece (>5 mm) inclined at an angle of 45° along with the horizontal outward cutter orientation. The dimensional accuracy (width of cut) and the workpiece deflection can be predicted more accurately during ball-end milling of thicker Inconel-718 workpiece inclined at higher angles.

Theoretical-Experimental Method for Determining the Material Damping Properties Based on the Damped Flexural Vibrations of Test Samples

Theoretical-experimental method is proposed in this paper for determining the logarithmic decrement of vibrations based on the measurement of tip amplitude of the flat cantilever test samples during their damped vibrations at first resonance mode. Significant effect of external aerodynamic forces on logarithmic decrement is observed. Extensive theoretical and experimental studies were performed on the aerodynamic component of damping of oscillated flat strip plates. For the assessment of its contribution to overall damping of test samples during their free vibrations, large number of numerical experiments were carried out on two dimensional flow dynamics around the plate, in the light of which an approximated empirical formula is found. Present study is also covering the method to identify the elastic properties and amplitude dependencies of logarithmic decrement on deformation in accordance with the data of physical experiments performed with various series of test samples.