Cantilever Type Research Articles

Cantilever type radio frequency microelectromechanical systems shunt capacitive switch design and fabrication

A new cantilever type radio frequency microelectromechanical systems (RF MEMS) shunt capacitive switch design and fabrication is presented. The mechanical, electromechanical, and electromagnetic designs are carried out to get <40 V actuation voltage, high isolation, and low insertion loss for 24 and 35 GHz and the fabrication is carried out for 24 GHz RF MEMS switch. The fabricated switch shows lower than 0.35 dB insertion loss up to 40 GHz and greater than 20 dB isolation at 22 to 29 GHz frequency band. An insignificant change is observed on RF performance at 24 GHz (ΔS11 ¼ 1 dB, ΔS21 < 0.1 dB) after 200°C thermal treatment for 30 min. The switch is fabricated on quartz wafer using an in-house surface micromachining process with amorphous silicon sacrificial layer structure. Total MEMS bridge thickness is aimed to be 4 μm and consists of 2-μm-thick sputtered and 2-μm-thick electroplated gold layers. The bridge bending models and pull-down voltage simula- tions are carried out for different stress levels and equivalent Young's modulus (Eavg). © 2015 Society of Photo-Optical

Parameter Optimization of Ball End Milling Process on Inconel 718 Using RSM and TLBO Algorithm

AbstractThis paper presents the application of Response Surface Methodology (RSM) coupled with Teaching Learning Based Optimization Technique (TLBO) for optimizing surface integrity of thin cantilever type Inconel 718 workpiece in ball end milling. The machining and tool related parameters like spindle speed, milling feed, axial depth of cut and tool path orientation are optimized with considerations of multiple response like deflection, surface roughness, and micro hardness of plate. Mathematical relationship between process parameters and deflection, surface roughness and microhardness are found out by using response surface methodology. It is observed that after optimizing the process that at the spindle speed of 2,000 rpm, feed 0.05 mm/tooth/rev, plate thickness of 5.5 mm and 15° workpiece inclination with horizontal tool path gives favorable surface integrity.

Sobol method application in dimensional sensitivity analyses of different AFM cantilevers for biological particles

Due to the more delicate nature of biological micro/nanoparticles, it is necessary to compute the critical force of manipulation. The modeling and simulation of reactions and nanomanipulator dynamics in a precise manipulation process require an exact modeling of cantilevers stiffness, especially the stiffness of dagger cantilevers because the previous model is not useful for this investigation. The stiffness values for V-shaped cantilevers can be obtained through several methods. One of them is the PBA method. In another approach, the cantilever is divided into two sections: a triangular head section and two slanted rectangular beams. Then, deformations along different directions are computed and used to obtain the stiffness values in different directions. The stiffness formulations of dagger cantilever are needed for this sensitivity analyses so the formulations have been driven first and then sensitivity analyses has been started. In examining the stiffness of the dagger-shaped cantilever, the micro-beam has been divided into two triangular and rectangular sections and by computing the displacements along different directions and using the existing relations, the stiffness values for dagger cantilever have been obtained. In this paper, after investigating the stiffness of common types of cantilevers, Sobol sensitivity analyses of the effects of various geometric parameters on the stiffness of these types of cantilevers have been carried out. Also, the effects of different cantilevers on the dynamic behavior of nanoparticles have been studied and the dagger-shaped cantilever has been deemed more suitable for the manipulation of biological particles.

A novel design for low insertion loss, multi-band RF-MEMS switch with low pull-in voltage

This paper presents a new type of capacitive shunt RF-MEMS switch. In the proposed design, float metal concept is utilized to reduce the RF overlap area between the movable structure and central conductor of CPW for improving the insertion loss of the device. This has been achieved without affecting the down-state response. Further, float metal also makes the down-state behavior predictable in terms of resonant frequency. For reducing the pull-in voltage, the switch is implemented with cantilever type of structure on either side of the transmission line. This structure also has the capability to inductively tune the isolation optimum value to the different bands and thus can be used in the reconfigurable RF systems. The device shows an insertion loss less than 0.10 dB, a return loss below 36.80 dB up to 25 GHz as compared to 1.00 dB insertion, 7.67 dB return loss for the conventional switch. In the OFF state, proposed device shows two isolation peaks i.e. 48.80 dB at 4.5 GHz and 54.56 dB at 9.7 GHz, when either or both cantilevers are electro-statically actuated to the down-state position respectively. The conventional device has a single isolation peak in the X-band. In addition, improvement of around 3 times in the bandwidth has also been achieved. The designed switch can be used at device and sub-system level for the future multi-band communication applications.

Nonlocal Timoshenko beam model for considering shear effect of van der Waals interactions on free vibration of multilayer graphene nanoribbons

In this study, shear effect of van der Waals (vdWs) interactions on free vibration of cantilever multi-layer graphene nanoribbons (MLGNRs) is investigated by using nonlocal Timoshenko beam model and molecular dynamics (MD) simulations. To this end, it is assumed that GNR layers of MLGNRs are perfectly bonded that no delamination will occur in layers interfaces. To calibrate the small scale parameter of the nonlocal Timoshenko model, the first two frequencies of armchair type cantilever MLGNRs with various layers and lengths are extracted using MD simulations and matched with those of the nonlocal Timoshenko theory. Comparing frequencies obtained by the MD simulation and the Timoshenko model shows that if values of the bending rigidity and the interlayer shear modulus (or equivalent shear modulus of Timoshenko theory) are taken as 1.20eV and 3.01GPa, respectively, then it will be possible to use the Timoshenko model for the free vibration analysis of MLGNRs. Moreover, it is observed that the calibrated nonlocal parameter is dependent on the number of MLGNR layers, and its calibrated value increases by increasing the number of GNR layers. This study helps researchers to analyze the mechanical behavior of MLGNRs in which the interlayer shear has apparent impact.

Thermo-magnetic behaviour of AFM–MFM cantilevers

Atomic force microscopy (AFM) experiments were performed to study the behaviour of AFM cantilevers under an external magnetic field B and temperature field produced by a coil with an iron core. Four cantilever types were studied. Forces were measured for different B values and at various coil-to-cantilever separation distances. The results were analysed on the basis of a phenomenological model. This model contains the contribution of two terms, one monopole–monopole interaction at short distance, and one apparent paramagnetic interaction in at large distance, which represents the temperature effects. We observe a good agreement between the model and the experimental data.

Calibration of the effective spring constant of ultra-short cantilevers for a high-speed atomic force microscope

Ultra-short cantilevers are a new type of cantilever designed for the next generation of high-speed atomic force microscope (HS-AFM). Ultra-short cantilevers have smaller dimensions and higher resonant frequency than conventional AFM cantilevers. Moreover, their geometry may also be different from the conventional beam-shape or V-shape. These changes increase the difficulty of determining the spring constant for ultra-short cantilevers, and hence limit the accuracy and precision of force measurement based on a HS-AFM. This paper presents an experimental method to calibrate the effective spring constant of ultra-short cantilevers. By using a home-made AFM head, the cantilever is bent against an electromagnetic compensation balance under servo control. Meanwhile the bending force and the cantilever deflection are synchronously measured by the balance and the optical lever in the AFM head, respectively. Then the effective spring constant is simply determined as the ratio of the force to the corresponding deflection. Four ultra-short trapezoid shape cantilevers were calibrated using this method. A quantitative uncertainty analysis showed that the combined relative standard uncertainty of the calibration result is less than 2%, which is better than the uncertainty of any previously reported techniques.

A microfluidic AFM cantilever based dispensing and aspiration platform

We present the development of a microfluidic AFM (atomic force microscope) cantilever-based platform to enable the local dispensing and aspiration of liquid with volumes in the pico-to-femtoliter range. The platform consists of a basic AFM measurement system, microfluidic AFM chip, fluidic interface, automated substrate alignment, external pressure control system and controlled climate near the dispensing area. The microfluidic AFM chip has a hollow silicon dioxide (SiO2) cantilever connected to an on-chip fluid reservoir at one end and a slicon nitride (Si3N4) tip with an aperture on the other end. A 3D printed plastic fluidic interface glued over the on-chip reservoir was used to connect microfluidics and macrofluidics. The fluidics is connected to an external pressure control system ranging from −0.8 bar to 5 bar with 0.1 bar resolution. This pressure range allows dispensing and aspiration of liquids through the cantilever tip aperture. The controlled climate with a temperature control range between 25°C – 40°C and humidity up to 95% near the dispensing area keeps the droplets for sufficiently long time before they evaporate. An array of droplets can be programmed to be dispensed automatically and access them again with a position accuracy of 1 micron. Experiments were performed with two types of cantilevers with different geometrical configurations. A minimum flow rate control of 50 fL/s was obtained and also frequency shift was monitored as the cantilever was filled with liquid. This platform will be used for various chemical and biological applications.

Accurate calibration and uncertainty estimation of the normal spring constant of various AFM cantilevers.

Measurement of force on a micro- or nano-Newton scale is important when exploring the mechanical properties of materials in the biophysics and nanomechanical fields. The atomic force microscope (AFM) is widely used in microforce measurement. The cantilever probe works as an AFM force sensor, and the spring constant of the cantilever is of great significance to the accuracy of the measurement results. This paper presents a normal spring constant calibration method with the combined use of an electromagnetic balance and a homemade AFM head. When the cantilever presses the balance, its deflection is detected through an optical lever integrated in the AFM head. Meanwhile, the corresponding bending force is recorded by the balance. Then the spring constant can be simply calculated using Hooke’s law. During the calibration, a feedback loop is applied to control the deflection of the cantilever. Errors that may affect the stability of the cantilever could be compensated rapidly. Five types of commercial cantilevers with different shapes, stiffness, and operating modes were chosen to evaluate the performance of our system. Based on the uncertainty analysis, the expanded relative standard uncertainties of the normal spring constant of most measured cantilevers are believed to be better than 2%.

A computational framework for the analysis of linear piezoelectric beams using hp-FEM

In this paper, a new computational framework is introduced for the analysis of three dimensional linear piezoelectric beams using hp-finite elements. Unlike existing publications, the framework is very general and suitable for static, modal and dynamic scenarios; it is not restricted to either actuation or energy harvesting applications and, moreover, it can cope with any anisotropy or electric polarisation orientation. Derived from first principles, namely the fundamental equations of continuum piezoelectricity, a new set of beam balance equations is presented based on a Taylor series expansion for the displacement and electric potential across the cross section of the beam. The coupled nature of the piezoelectric phenomenon at a beam level arises via a series of mechanical (and electrical counterparts) stress and strain cross sectional area resultants. To benchmark the numerical algorithm, and in order to aid prospective researchers, a new closed-form solution is presented for the case of cantilever type systems subjected to end tip mechanical/electrical loads. To the best of the authors’ knowledge, the analytical solution for this prototypical example has not been previously presented. Finally, some numerical aspects of the hp-discretisation are investigated including the exponential convergence of the hp-refinements and the consideration of linear or quadratic electric potential expansions across the cross section of the beam.

Modal method for dynamics analysis of cantilever type structures at large rotational deformations

The modal warping method is extended to a floating frame of reference formulation to combine modal warping formula with rigid body simulation. The highly nonlinear mass matrix because of the inertia coupling between the reference and the elastic displacements is approximated using the linear theory of elastodynamics. By kinematics analysis of infinitesimal deformation, the calculation of rotation deformations is derived. Then modal warping method is used to model deformations for numerical accuracy and computation efficiency. The rigid-flex multibody model for a leaf spring landing gear system is developed. The accuracy of the proposed method is examined by experimental/simulation comparison.

Analysis of the adhesion effect in RF-MEMS switches using atomic force microscope

The main scope of this paper is to investigate the adhesion effect on the mechanical response of MEMS components from RF switch application by using an atomic force microscope (AFM). The occurrence and strength of adhesion effects in MEMS devices depend on a variety of environmental, geometrical and operational parameters (temperature, relative humidity, contact area, surface energies of contact materials, surface roughness and shape of contact surfaces) — so-called adhesion parameters should be taken into account when investigating the reliability of MEMS devices with respect to adhesion-induced failures. After, the temperature influence on adhesion is experimentally analyzed considering commonly used MEMS materials to fabricate RF switches. The adhesion force is the main factor with influence on stiction. In fact, stiction is the adhesion occurring between the contact surfaces due to surface forces including van der Waals, capillary forces, Casmir forces, and electrostatic forces. First, the adhesion between AFM tip and the materials under interest is investigated using the spectroscopy in point of an atomic force microscope. Different coated AFM tip is considered for tests. The AFM spectroscopy-in-point curve gives the direct measurement of tip-sample interaction force as a function of the gap between the tip and sample. The adhesion between tip and sample is characterized by so-called pull-off or pull-out force. The pull-off force is related in current continuum contact mechanics model to the work of adhesion. Using a thermal controller stage the temperature of investigated materials is changed from 0°C to 80°C. The mechanical properties variation of MEMS materials as a function of temperature is monitored and the temperature influence on adhesion is analyzed. The influence of the surface roughness on the adhesion forces between AFM tip and samples is determined. Different roughness (Ra) of investigated polysilicon samples is varied in the range of ∼5–15 nm. The adhesion force between Si 3 N 4 and these surfaces increases from 0.94nN to 12.72nN if the roughness decreases from 12nm to 7nm. In order to compare the influence of cantilever type of adhesion testing was done on several samples of the gold using two kinds of cantilevers. As the roughness decreases, the adhesion force increases, respectively. A high value of adhesion force is determined for the contact between gold AFM tip and gold sample comparatively with the contact between Si 3 N 4 AFM tip and gold material. This difference is based on the surface energy of materials. After material testing, flexible MEMS component used in RF switches is investigated in order to determine the adhesion force between him and the substrate. The contact areas between an AFM tip and substrate is an important parameter for analyzing the adhesion effect. The results from laboratory indicate that the adhesive force increases if the surface roughness decreases because the contact area increases, respectively. The adhesion between microcantilever and substrate is obtained based on experimental tests of 11.675μN.

Technology for Fast Fabrication of Glass Microhotplates Based on the Laser Processing

In this paper, we describe a novel cost-effective and simple technology for the production glass MEMS applied as microhotpalte platform for metal oxide gas sensors. The basis of the technology is magnetron sputtering of platinum heating layer followed by precise laser engraving and cutting used for heater patterning. As a result of the technology, we demonstrate the glass microhotplate cantilever with thickness of 30μm equipped with platinum microheater with dimension of about 500×500μm. The cantilever type MEMS microhotplate demonstrate very high stability at working temperatures up to 600 0C, which gives possibility to use it for the low-scale fabrication microhotplate of metal oxide gas sensors.

模态方法下的悬臂梁/类悬臂梁弹性构件的动力学建模

模态方法下的悬臂梁/类悬臂梁弹性构件的动力学建模

Additive Technologies for Ceramic MEMS Sensors

The application of MEMS technology for the fabrication of MOX sensors with low power consumption becomes now a very important trend in gas sensor design. However, traditional silicon technology has some evident disadvantages, when applied in high-temperature devices produced in limited batch. We present our attempt to combine the advantages of ceramic MEMS technology (high working (600°C) and technological treatment (1000°C) temperature, chemical stability at high temperature) with the advantages of additive technologies for the fabrication of functional elements of gas sensor (heaters, sensing, and catalytic layers). We developed conductive silver, gold and platinum nanoparticle (10–30nm) inks usable in ink and aerosol jet printers and demonstrated the possibility to fabricate narrow conductive lines of microheaters and electrodes of sensor (line width ∼ 35μm). The combination of jet printing onto thin ceramic substrate with laser cutting enables the fabrication of advanced cantilever type sensors operating in pulsing heating mode.

Investigations on metrological characterization of elliptical shaped force transducers for precision force measurement

Article history: Received 6 April, 2015 Accepted 20 July 2015 Available online 21 July 2015 Force measurement is very vital in various scientific applications and its precise measurement is very necessary for reliability of the measurement process. There are several types of simple shaped force transducers, which may range from ring shaped force transducers to cantilever type or beam type force transducers. Ring shaped force transducers are one of most commonly used type of force transducers are developed on the basis of theory of thin rings. Till today, some of the modifications of ring shaped force transducers have been reported, the present investigation discusses the development of elliptical shaped force transducer as a modification of ring shaped force transducers and its preliminary investigation on metrological characterization based on the calibration procedures according to standards ISO 376-2011. The force transducer has been developed for the nominal capacity of 20 kN and strain gauges have been applied over the optimum locations to minimize cross sensitivity. The force transducer is developed exclusively for static force measurement related applications to serve as a link in providing the traceability to the user industries and calibration laboratories or serve as force transfer standard. The force transducer has been evaluated for suitability as a precision force transducer with the help of the 50 kN Dead Weight force machine traceable to national standard of force. The elliptical shape force transducers are found to have comparable metrological characteristics as compared to other ring shape force transducers. © 2015 Growing Science Ltd. All rights reserved.

Prediction of solidification cracking in laser welds of type 310 stainless steels

The occurrence of solidification cracks in laser welds of type 310 stainless steels was predicted by numerical analyses of the solidification brittle range (ductility curve for cracking) and thermal strain in the weld metal. The solidification brittle range in laser welding was estimated from that in arc welding based on the numerical analyses of supercooling (for calculating dendrite tip temperature) and segregation (for calculating completely solidified temperature) during rapid solidification. The calculated solidification brittle range was reduced with an increase in the welding speed because of the enhanced supercooling and the inhibited solidification segregation. The thermal strain analysis by FEM suggested that solidification cracks would occur in SUS310S welds at laser travelling velocity of 60 mm/s applying the initial strain of 1.5%, while no solidification cracks in SUS310EHP welds at any laser travelling velocities applying the higher initial strain of 2.2%. The cantilever type cracking test in laser welding revealed that the predicted results of occurrence of solidification cracks were consistent with experimental ones.

Vibrational analysis of single-layered piezoelectric AFM microcantilever in amplitude mode by considering the capillary force

In this article, the vibrational behavior of a microcantilever (MC) with an extended piezoelectric layer in the air ambient undergoes examination. To model the vibrational motion of this type of cantilever, the Hamilton’s principle has been used. For this purpose, the MC vibrational equation has been derived by the assumption of the continuous beam based on the Euler-Bernoulli beam theory. By adopting the finite element method (FEM), the MC differential equation has been solved. In the present simulation not only van der Waals and contact forces but also the capillary forces resulting from the condensation of the water vapors in air on MC tip have been considered. The results illustrate that the force between the sample surface and the probe affects the MC amplitude; furthermore, it causes the reduction in the resonance frequency. In addition, to reduce the time delay during topography from the surface roughness, it is better to select MCs with larger width and length and smaller thickness. Furthermore, the results indicate that the best imaging takes place when the vibration is in its second vibrational mode. Finally, the effects of MC geometric parameters on the time delay between the starting moment of surface roughness and the moment of variation in the MC amplitude (surface roughness topography) have been analyzed.

Weighing System Design Based on Single Chip Microcomputer

As the living standards of people improve continually, commercial behavior is becoming more and more modernized, people also put forward new requirements for the speed and accuracy of goods measurement. This paper designs a weighing system of digital electronic scale which is similar to the MCU simulation, and gives the design diagram, hardware composition and software system. This system takes the 51 single chip microcomputer as the core, the main components are the dedicated 24 bits serial A/D conversion chip HX711, cantilever type resistance strain sensor, the four digital tube display. This design uses the dedicated 24 bits serial A/D conversion chip HX711, which has high resolution, simple peripheral interface, and occupies less I/O port, etc.

Resonance properties of metallic nanocantilevers

Resonant properties of the three-layer metallic cantilevers with 40-120 nm thickness were investigated. Two types of cantilevers were fabricated: Cr/Al/Cr and Ti/Al/Ti. Dependencies of the fundamental resonant frequency and Q-factor on the cantilever length, width and thickness were experimentally obtained. The experimental data analysis and the comparison with the theoretical predictions were performed. Dependence of material properties on the cantilever thickness was not observed. Energy losses in the surface layer of the cantilever were the dominant energy loss mechanism.