Super Sensitive Mass Detection in Nonlinear Regime

Investigations concerning a coagulation sensor based on shear horizontal surface acoustic waves (SH-SAW) are described. As a first step, experimental work was focused on a simpler system: a quartz crystal micro balance (QCM) also called thickness shear mode resonator (TSM). In the literature the suitability of such devices for the characterization of coagulation process is already described. Coagulation tests like Quick and activated partial thromboplastin time (aPTT) have been performed at a resonance frequency of 9 MHz. In a further step, smaller changes in resonant frequency with smaller concentration of fibrinogen could be shown with plasma dilution tests. While performing measurements with different sample volumes the coagulation process was still detectable with five microlitres of blood plasma. A special measurement cylinder was designed and tested to separate the sample from environmental influences. Performing all these tests with plasma or whole blood samples leads to similar results. For determination of the coagulation time, the steepest decrease of resonance frequency vs. time was found as a reproducible value. Measurements have been done at the overtones of the TSM in order to study whether the hemostasis is still measurable at frequencies common to SAW devices. The coagulation process could be measured up to 243 MHz (overtone 27) although the decay length decreases with higher frequencies. Tests using SAW devices with SH-SAW resonator filters (36°rotYX-LiTaO3 substrate) have been done at 168 MHz. The electrolytic character of the plasma caused damage to the electrode structure which could be avoided at later tests. Afterwards the blood coagulation process was successfully measured with SH-SAW. Finally a specially adapted SH-SAW sensor was designed, constructed and tested. Compared to TSM resonators vibrating on the fundamental mode, sensitivity was greatly increased.

The flux of vacuum ultraviolet (VUV) and ultraviolet (UV) photons from a hydrogen plasma was detected by fluorescence measurements of sodium salicylate sheets with and without a MgF2 window. In order to expose the samples to the same photon flux in all experiments, the power input to the microwave plasma source was adjusted. Polyethylene (PE), polypropylene (PP), and polystyrene (PS) were treated with VUV radiation or with a remote hydrogen plasma. The mass loss and the CH-absorption loss were recorded by in situ quartz crystal micro balance and by in situ IR reflection absorption spectroscopy, respectively. The VUV irradiation and plasma treatment caused similar effects in the case of PE, PP showed an increased polymer ablation in plasma treatments, and for PS a negligible loss in mass and CH absorption was detected in plasma and VUV treatments.

Components of a lubricant are divided into base oil and additives. Base oil dominates basic fluid properties of a lubricant. Additives support to improve the lubrication performance of oils. Oiliness additives have the friction decreasing effect due to the formation of the adsorption layer preventing contact of the sliding surfaces. Previous studies about oiliness additives were performed using a single additive in base oil. However, commercial lubricant contains several additives, which interacts each other. The interaction between the additives is not elucidated. In this research, tribological characteristics of adsorption layers of stearic acid, oleic acid and the mixture of both of them were studied for elucidating the interaction of the additives by using a pendulum type friction tester, AFM (Atomic Force Microscopy) and QCM (Quartz Crystal Micro balance). The friction reduction effect of mixed additives was higher than that of single additives. In case of the mixed additives, the ratio of oleic acid and stearic acid was calculated to be 2:3 by each occupied area in the adsorption layer. The relationship between the adsorption property and friction behavior was discussed based on the experimental results.

The frequency tuning of a surface micromachined film bulk acoustic resonator (FBAR), which integrates the tunable series capacitor and the piezoelectric resonating layer, had been demonstrated in previous publications. In the proposed structure, a movable piezoelectric cantilever is suspended above a bottom electrode. The air gap between the cantilever and the bottom electrode functions both as a tunable capacitor and an acoustic isolation. However, in case of electrostatic actuation, continuous tuning is limited in the range before the pull-in of the cantilever and is very small in prior art. In this paper, an improved design is suggested. By changing the the effective area ratio between the tunable capacitor and the piezoelectric resonating film, a larger continuous tuning range of 24.5MHz (0.39%) at a resonating frequncy of about 6.3GHz is realized. I. INTRODUCTION Film bulk acoustic resonators (FBARs) are microma- chined versions of the conventional piezoelectric resonators such as quartz crystals, with the advantages of small size, high frequency capability, high quality factor and CMOS- compatibility. In order to compensate for drifts from different origins such as aging, temperature change and fabricational inhomogeneities, a small range of frequency tuning is desired. Frequency tuning of a surface micromachined FBAR by electrostatic actuation has been designed and demonstrated in earlier works (1), (2), in which a vertically movable piezoelectric layer with a top electrode is suspended above a bottom electrode, as shown in Fig. 1. The air gap between the piezoelectric layer and the bottom electrode serves both as a tunable capacitor and as an acoustic isolation. Frequency tuning is realized by applying a DC voltage between the top and bottom electrode to electrostatically displace the suspended piezoelectric layer and thus change the air gap capacitance and the frequency response of the device. This design however only displays a very small continuous tuning range because of the pull-in of the cantilever by electrostatic actuation. In earlier works (2), only 1.9MHz (∼0.03% )o f continuous tuning was achieved before pull-in takes place. It is thus necessary to revise the design to meet the demand of a larger (> 0.2%) continuous tuning range. II. THE PRINCIPLE OF TUNING The electrical characteristics of an FBAR near its funda- mental mode of resonance can be approximated by a lumped- element circuit as shown in Fig. 2(a), in which the series RF signal+DC voltage

Nonlinear frequency shift behavior of graphene–elastic–piezoelectric laminated films as a nano-mass detector

ABSTRACTFormulated, processed, and dried Aloe polysaccharides thin film sandwiched between ITO as bottom electrode and Au as top electrode has been adopted as an artificial synapse to emulate behavior of neuromorphic computing. The synaptic plasticity or weight has been modulated with this simple metal-insulator-metal structure by applying voltage sweep and voltage pulse, with excitatory postsynaptic current being monitored. Synaptic potentiation and depression has been demonstrated by applying 6 consecutive sweeps of voltage in positive and negative polarity, respectively. By varying number (10 – 50) of voltage pulses, variable synaptic weight has been measured with paired pulse facilitation and post-tetanic potentiation indexes of 2.61x10-6and 1.45x10-4, respectively. The short-term plasticity and long-term potentiation can be clearly revealed when applying 40 pulses and beyond, with extracted time constants of approximately 28 s at 40 pulses and 90 s at 50 pulses.

Monitoring of anticancer effect of cisplatin and 5-fluorouracil on HepG2 cells by quartz crystal microbalance and micro CCD camera

Presented herein is an investigation for the nonlinear vibration and stability analysis of rotating functionally graded (FG) piezoelectric nanobeams based on the nonlocal strain gradient theory. The present model can be regarded as a simplified version for the rotating nanowire of biomechanical nanogenerators. The Hamilton principle is used to derive nonlinear equations of motion and their related boundary conditions, which are then discretized to form a set of algebraic equations. Accordingly, the nonlinear vibration frequencies and buckling loads of the nanobeams can be determined by an iterative method. A parametric study of rotational velocity, nonlocal parameter, material length parameter, power-law index, and electrostatic voltage on the dynamic stability behavior of such nanobeams is also presented. In the cantilever case, increasing the nonlocal parameter and material length parameter can result in a stiffness-hardening effect that is unaffected by rotational velocity and the material length parameter to nonlocal parameter ratio. Yet, this has not been reported previously. More importantly, incorporating the effect of geometric nonlinearity on the dynamic responses and stability results of the nanobeams is indispensable. In particular, new observations for the coupling effect of vibration amplitude and power-law index on the electric potential effect are useful for the design of rotating microelectromechanical devices.

Plasma display panels (PDPs) are composed of miniature gas discharge devices sustained in noble gas mixtures. In this paper, the dynamics of a coplanar-electrode PDP cell are described using results from a two-dimensional computer simulation. During the first voltage pulse, the discharge takes place between the top and bottom electrodes. Due to charging of the bottom dielectric during the first discharge pulse, a surface discharge takes place between the top coplanar electrodes on successive pulses.

Resistive random access memories (RRAMs) can be programmed to discrete resistive levels on demand via voltage pulses with appropriate amplitude and widths. This tuneability enables the design of various emerging concepts, to name a few: neuromorphic applications and reconfigurable circuits. Despite the wide interest in RRAM technologies there is still room for improvement and the key lies with understanding better the underpinning mechanism responsible for resistive switching. This work presents a methodology that aids such efforts, by revealing the nature of the resistive switching through assessing the transport properties in the non-switching operation regimes, before and after switching occurs. Variation in the transport properties obtained by analysing the current-voltage characteristics at distinct temperatures provides experimental evidence for understanding the nature of the responsible mechanism. This study is performed on prototyped device stacks that possess common Au bottom electrodes, identical TiO2 active layers while employing three different top electrodes, Au, Ni and Pt. Our results support in all cases an interface controlled transport due to Schottky emission and suggest that the acquired gradual switching originates by the bias induced modification of the interfacial barrier. Throughout this study, the top electrode material was found to play a role in determining the electroforming requirements and thus indirectly the devices’ memristive characteristics whilst both the top and bottom metal/oxide interfaces are found to be modified as result of this process.

This article is concerned with the development of a distributed model based on the modified strain gradient elasticity theory (MSGT), which enables us to investigate the size-dependent pull-in instability of circular microplates subjected to the uniform hydrostatic and nonuniform electrostatic actuations. The model developed herein accommodates models based on the classical theory (CT) and modified couple stress theory (MCST), when all or two material length scale parameters are set equal to zero, respectively. On the basis of Hamilton's principle, the higher-order nonlinear governing equation and corresponding boundary conditions are obtained. In order to linearize the nonlinear equation, a step-by-step linearization scheme is implemented, and then the linear governing equation is discretized along with different boundary conditions using the generalized differential quadrature (GDQ) method. In the case of CT, it is indicated that the presented results are in good agreement with the existing data in the literature. Effects of the length scale parameters, hydrostatic and electrostatic pressures, and various boundary conditions on the pull-in voltage and pull-in hydrostatic pressure of circular microplates are thoroughly investigated. Moreover, the results generated from the MSGT are compared with those predicted by MCST and CT. It is shown that the difference between the results from the MSGT and those of MCST and CT is considerable when the thickness of the circular microplate is on the order of length scale parameter.

Modal analysis of viscoelastic three-dimensional rotating beam with generic tip mass

Because of fasttechnological development, electrostatic nanoactuator devices like nanosensors, nanoswitches, and nanoresonators are highly considered by scientific community. Thus, this article presents a new solution technique in solving highly nonlinear integro-differential equation governing electrically actuated nanobeams made of functionally graded material. The modified couple stress theory and Gurtin–Murdoch surface elasticity theory are coupled together to capture the size effects of the nanoscale thin beam in the context of Euler–Bernoulli beam theory. For accurate modelling, all the material properties of the bulk and surface continuums of the FG nanoactuator are varied continuously in thickness direction according to power law. The nonlinearity arising from the electrostatic actuation, fringing field, mid-plane stretching effect, axial residual stress, Casimir dispersion, and van der Waals forces are considered in mathematical formulation. The nonlinear nonclassical equilibrium equation of FG nanobeam-based actuators and associated boundary conditions are exactly derived using Hamilton principle. The new solution methodology is combined from three phases. The first phase applies Galerkin method to get an integro-algebraic equation. The second one employs particle swarm optimization method to approximate the integral terms (i.e. electrostatic force, fringing field, and intermolecular forces) to non-integral cubic algebraic equation. Then, solved the system easily in last phase. The resulting algebraic model provides means for obtaining critical deflection, pull-in voltage, detachment length, minimum gap, and freestanding effects. A reasonable agreement is found between the results obtained from the present method and those in the available literature. A parametric study is performed to investigate the effects of the gradient index, material length scale parameter, surface energy, intermolecular forces, initial gap, and beam length on the pull-in response and freestanding phenomena of fully clamped and cantilever FG nanoactuators.

The paper describes an electrically tunable and switchable film bulk acoustic resonator (FBAR) that is formed by integrating an FBAR with an electrostatic MEMS actuator. Around /spl sim/0.8% tuning of the series resonant frequency (/spl Delta/f/spl cong/18 MHz) at 2.3 GHz is experimentally obtained with an electrostatic actuation voltage varying between 12.2 and 27.5 V. Also, a switchable resonator with Q (quality) factor of greater than 100 at 2.2 and 4.0 GHz is experimentally demonstrated in a compact device area.

The impetus of the study is to present a novel micro electro mechanical system based tunable gyroscope with the possibility of sensitivity enhancement using appropriate electrostatic hopping voltages. The proposed model is a silicon-based clamped–clamped micro beam sandwiched with two piezoelectric layers throughout the entire length. The nonlinear electrostatic forces are applied to the micro beam along its sense and drive mode directions (either lateral sides). The drive mode actuation is a combination of a direct current (DC) and an alternating current voltage; whereas the sense mode actuation is a pure DC voltage. The micro beam oscillates along the drive mode due to the harmonic drive mode excitation; as the micro beam undergoes base rotation, the Coriolis force induces another motion in the direction of the sense mode which is perpendicular to the drive mode direction. The more is the amplitude of the base rotation, the more is the sense mode amplitude. The sense mode amplitude is directly attributed to the magnitude of base rotation. The piezoelectric layers are actuated by a DC voltage which leads to an axial force proportional to the applied DC voltage. Exciting the piezoelectric layers changes the overall stiffness of the micro beam and as a result the operating frequency of the gyroscope becomes tunable. The partial differential equation of the motion is derived using Hamiltonian principle and discretized into two nonlinear ordinary differential equations along the drive and sense mode directions. The shooting method is used to capture the periodic motion orbits and accordingly the frequency response curves. By using Floquet theory the stability of the periodic orbits is determined. Due to the nonlinearity of the governing equations in the vicinity of the primary resonance, the gyroscope exhibits multi-response solution; Applying appropriate hopping voltages, the micro beam is pushed into the attraction basin of the response with higher amplitude and accordingly the sensitivity of the gyroscope is enhanced. The proposed gyroscope not only has the capability of having improved sensitivity but also its operating frequency can be tuned both in forward and backward directions by means of applying appropriate piezoelectric voltage with an appropriate polarity.