Strong Mechanical Coupling Research Articles

Progress in the Construction of the 43 T Hybrid Magnet at LNCMI-Grenoble

By combining resistive polyhelix and Bitter insert coils with a large bore superconducting outsert one, the new hybrid magnet in construction at LNCMI-Grenoble will produce an overall continuous magnetic field of 43 T in a 34-mm warm bore aperture. After a brief reminder of the specificity of hybrid magnets, namely the strong electromagnetic and mechanical coupling between resistive and superconducting coils, the main specificities of the proposed design are presented. The superconducting coil of 1.1-m cold bore diameter will provide a nominal magnetic field of at least 8.5 T. It relies on the specific development of the Nb–Ti/Cu Rutherford cable on a conduit conductor (RCOCC) cooled down to 1.8 K by a bath of superfluid helium pressurized at 1200 mbar. The novelty of the RCOCC concerns the in-laboratory assembly with induction soft-soldering of the Rutherford cable on a Cu–Ag hollow stabilizer, allowing a strict control of the quantity of the solder alloy used and therefore of the interstrand contact resistance. A stainless steel reinforced copper shield inserted between the superconducting and resistive coils will reduce the coupling currents induced within the RCOCC, as well as the mechanical force exerted on the superconducting coil. After successful thorough reviews of the Grenoble hybrid magnet design anticipating possible upgrades of the maximum magnetic field that can be produced, this project is now well engaged in its construction phase. The status of this project is presented in details together with the next milestones.

Strong 4-mode coupling of nanomechanical string resonators

We investigate mechanical mode coupling between the four fundamental flexural modes of two doubly clamped, high-Q silicon-nitride nanomechanical string resonators. Strong mechanical coupling between the strings is induced by the strain mediated via a shared clamping point, engineered to increase the exchange of oscillatory energy. One of the resonators is controlled dielectrically, which results in strong coupling between its out-of-plane and in-plane flexural modes. We show both inter-string out-of-plane-in-plane and 3-mode resonances of the four coupled fundamental vibrational modes of a resonator pair, giving rise to a simple and a multimode avoided crossing, respectively.

Concurrent Rupture of Two Molecular Bonds in Series: Implications for Dynamic Force Spectroscopy

The immobilization of receptor–ligand molecules in dynamic force spectroscopy (DFS) often relies on an extra noncovalent linkage to solid surfaces, resulting in two barrier-crossing diffusion processes in series and concurrent bond dissociations. One outstanding theoretical issue is whether the linkage between the immobilizer and biomolecule is sufficiently strong during repeated force ramping in the measurements and how it might influence the interpretation on receptor–ligand kinetics. Following the classical framework by Kramers, we regard each dissociation process as a flux of probabilistic bond configuration outward over an energy barrier in the coordinated energy landscape, and solve the two coupled boundary value problems in the form of Smoluchowski equation. Strong kinetic and mechanical coupling is observed between the two molecular bonds in series, with the results showing that involving a noncovalent linkage in DFS can obscure the unbinding characteristics of the receptor–ligand bond. Our approach provides a quantitative assessment to the hidden effects of having a fragile molecular anchorage in DFS and allows the corrected interpretation on receptor–ligand dissociation kinetics in the case.

A Bistable Microelectromechanical System Actuated by Spin‐Crossover Molecules

AbstractWe report on a bistable MEMS device actuated by spin‐crossover molecules. The device consists of a freestanding silicon microcantilever with an integrated piezoresistive detection system, which was coated with a 140 nm thick film of the [Fe(HB(tz)3)2] (tz=1,2,4‐triazol‐1‐yl) molecular spin‐crossover complex. Switching from the low‐spin to the high‐spin state of the ferrous ions at 338 K led to a reversible upward bending of the cantilever in agreement with the change in the lattice parameters of the complex. The strong mechanical coupling was also evidenced by the decrease of approximately 66 Hz in the resonance frequency in the high‐spin state as well as by the drop in the quality factor around the spin transition.

A Bistable Microelectromechanical System Actuated by Spin-Crossover Molecules.

We report on a bistable MEMS device actuated by spin-crossover molecules. The device consists of a freestanding silicon microcantilever with an integrated piezoresistive detection system, which was coated with a 140 nm thick film of the [Fe(HB(tz)3 )2 ] (tz=1,2,4-triazol-1-yl) molecular spin-crossover complex. Switching from the low-spin to the high-spin state of the ferrous ions at 338 K led to a reversible upward bending of the cantilever in agreement with the change in the lattice parameters of the complex. The strong mechanical coupling was also evidenced by the decrease of approximately 66 Hz in the resonance frequency in the high-spin state as well as by the drop in the quality factor around the spin transition.

Multiferroic heterostructures of Fe3O4/PMN-PT prepared by atomic layer deposition for enhanced interfacial magnetoelectric couplings

In this work, multiferroic heterostructures have been prepared by in situ growing oxide magnetic films on ferroelectric single crystal substrates using atomic layer deposition (ALD). Strong interfacial mechanical coupling between the magnetic and ferroelectric phases has been created, arising from the formation of chemical bonds at the interface due to the nature of layer-by-layer self-limiting growth mechanism of the ALD technique. An enhanced magnetoelectric (ME) coupling has been achieved, which allows an electric field to robustly switch magnetic anisotropy up to 780 Oe. In addition, electrical impulse non-volatile tuning of magnetism has also been realized through partially coupled ferroelectric/ferroelastic domain switching. The ALD growth of magnetic oxide films onto ferroelectric substrates provides an effective platform for the preparation of multiferroic heterostructures at low temperatures with an improved ME coupling, demonstrating a great potential for applications in 3D spintronics, microelectronics and data storages.

Performance investigation of cement-based laminated multifunctional magnetoelectric composites

In this paper, cement-based multifunctional magnetoelectric (ME) composite with the laminated structure of one lead zirconate titanate (PZT) layer sandwiched between two cement-based Tb1−xDyxFe2 alloy (Terfenol-D) layers has been successfully fabricated for the first time in the world. Furthermore, systematic investigation has been conducted on the overall performance of this newly developed composite. The dielectric and piezoelectric behaviors of this composite are equivalent to those of pure PZT, which dominates the ferroelectric properties of composite. A giant ME response is observed in the composite because of the strong mechanical coupling interaction among different phases detected by fiber Bragg grating sensing technique. The measured maximum ME sensitivity αE33 can reach up to 1.071V/cmOe under 3000Oe Hdc field at low frequency with fv=0.30 of Terfenol-D in the composite, which is much superior to that of other polymer-based composites (just about 200–300mV/cm·Oe) reported. Such great ME sensitivity can be attributed to that cement functions not only as particles binder, but also as the transmission medium with higher transfer efficiency. Such excellent performances make this novel ME composite be a strong potential candidate for engineering applications as sensors, actuators and other smart transducers.

Cooperating Robot Force Control for Positioning and Untwisting of Thin Walled Components

Geometric deformations in large thin walled components such as airplane shells caused by gravitational influences have to be compensated before assembly. The research objective is to develop a metrology assisted robot based assembly system that detects deformations and compensates them through force controlled movements of the robots. This paper describes the development of a cooperating robot force control for three industrial robots. The control algorithm uses a numerical optimization to take into account the strong mechanical coupling of the robots by the handled component.

Mapping seismic moment and b-value within the continental-collision orogenic-belt region of the Iranian Plateau

In this paper, high-resolution map of the Gutenberg–Richter b-value and seismic moment-release are provided for the Iranian Plateau using the unified and homogeneous part of the seismicity record of the region (January 1995–July 2016). We use these parameters as stressmeters and qualitatively explore their correlations with the GPS velocity field, strain rate, faulting mechanism, attenuation, and structure of the region. Our goal is to reveal the correlations and anomalous patterns that can help to better understand the seismotectonics and the state of present-day crustal stress within the region. A negative correlation between b-value and seismic moment release as well as convergence rates is found. Correlation between geodetic measurements and seismic observations might indicate the existence of a strong mechanical coupling between the basement and the sediment cover across Zagros. High geodetic strain rates east of the Hormuz strait, southern central Alborz, and along the north Tabriz fault correspond to low b-value anomalies at these areas. A strong low b-value anomaly is observed at the major tectonic discontinuity between the Zagros continental collision and the oceanic Makran subduction.

Electrostatic energy harvesting device with dual resonant structure for wideband random vibration sources at low frequency.

In this paper, we present design and test of a broadband electrostatic energy harvester with a dual resonant structure, which consists of two cantilever-mass subsystems each with a mass attached at the free edge of a cantilever. Comparing to traditional devices with single resonant frequency, the proposed device with dual resonant structure can resonate at two frequencies. Furthermore, when one of the cantilever-masses is oscillating at resonance, the vibration amplitude is large enough to make it collide with the other mass, which provides strong mechanical coupling between the two subsystems. Therefore, this device can harvest a decent power output from vibration sources at a broad frequency range. During the measurement, continuous power output up to 6.2-9.8 μW can be achieved under external vibration amplitude of 9.3 m/s2 at a frequency range from 36.3 Hz to 48.3 Hz, which means the bandwidth of the device is about 30% of the central frequency. The broad bandwidth of the device provides a promising application for energy harvesting from the scenarios with random vibration sources. The experimental results indicate that with the dual resonant structure, the vibration-to-electricity energy conversion efficiency can be improved by 97% when an external random vibration with a low frequency filter is applied.

One Binder to Bind Them All.

High quality binders, such as antibodies, are of critical importance for chemical sensing applications. With synthetic alternatives, such as molecularly imprinted polymers (MIPs), less sensor development time and higher stability of the binder can be achieved. In this feature paper, I will discuss the impact of synthetic binders from an industrial perspective and I will challenge the molecular imprinting community on the next step to leapfrog the current status quo of MIPs for (bio)sensing. Equally important, but often neglected as an effective chemical sensor, is a good match of transducer and MIP coating for a respective application. To demonstrate an application-driven development, a biosensing use case with surface-imprinted layers on piezoacoustic sensors is reported. Depending on the electrode pattern for the transducer, the strong mechanical coupling of the analyte with the MIP layer coated device allows the adoption of the sensitivity from cell mass to cell viability with complete reversibility.

Static and Dynamic Amplification Using Strong Mechanical Coupling

Amplifying the signal-to-noise ratio of resonant sensors is vital toward the effort to miniaturize devices into the sub-micro and nano regimes. In this paper, we demonstrate theoretically and experimentally, amplification through mechanically coupled microbeams. The device is composed of two identical clamped-clamped beams, made of polyimide, connected at their middle through a third beam, which acts as a mechanical coupler. Each of the clamped–clamped microbeams and the coupler are designed to be actuated separately, hence providing various possibilities of actuation and sensing. The coupled resonator is driven into resonance near its first resonance mode and its dynamic behavior is explored via frequency sweeps. The results show significant amplification in the resonator amplitude when the signal is measured at the midpoint of the coupler compared with the response of the individual uncoupled beams. The static pull-in characteristics of the resonator are also studied. It is shown that the compliant mechanical coupler can serve as a low-power radio frequency switch actuated at low voltage loads. [2016-0100]

Fabrication and characterization of (111)-epitaxial Pb(Zr0.35Ti0.65)O3/Pb(Zr0.65Ti0.35)O3 artificial superlattice thin films

Artificial superlattice thin films consisting of two different compositions of Pb(Zr,Ti)O3 (PZT), which are in tetragonal and rhombohedral phases at room temperature in the bulk state, were grown on (111)cSrRuO3/(111)SrTiO3 by pulsed laser deposition. Fairly perfect periodicity with sharp interfaces was observed by X-ray diffraction and scanning transmission electron microscopy. It was found that the film with each layer of 5 nm thickness had a single-domain structure for both PZT layers, which would arise from the strong mechanical and electrical coupling between PZT layers. The fabricated superlattice thin films showed saturated P–E hysteresis curves. Larger electromechanical response was observed in the films with smaller layer thickness.

Higher resonant mode effect on the performance of piezo actuated 2-DOF rectangular cantilever shaped resonators (2-DOF RCR) for liquid viscosity and density sensing

According to the demand for a highly sensitive resonant sensor, a 2-DOF RCR (2-degrees of freedom rectangular cantilever shaped resonators) with higher resonant mode of vibration is developed for sensing of liquid viscosity and density. The measurement principle is based on tracking the resonant characteristics of 2-DOF RCR system which depends on the density and viscosity of liquids it operates in. The 2-DOF RCR consists of a driver and absorber mass of identical natural frequency with a disparity in mass and connected by a strong mechanical coupling unit, thus the resonant amplitude and resonant frequency is enhanced at 1st mode compared with 1-DOF (1-degree of freedom) system. For further improving the sensitivity performance, the 3rd resonant mode vibration of 2-DOF RCR system is investigated. The system is evaluated for its performance in liquids of viscosity ranging from 0.23 to 1400 mPas and density ranging from 713 to 1261 kg/m3 at 3rd mode and compared with 1st mode of vibration. Good agreement with the simulated results from theoretical model and experimental results is reported and the enhanced performance of 2-DOF RCR system by using higher mode is also confirmed. Compared to the 1st mode, the sensitivity in terms of resonant frequency against density is improved with 22.75 % and 19 % in aqueous based and oil based liquids respectively and the sensitivity in terms of quality factor against viscosity is improved by 22.4 % and 30 % in aqueous and oil based liquids, at 3rd mode of vibration.

Bi-resonant structure with piezoelectric PVDF films for energy harvesting from random vibration sources at low frequency

This paper reports on a bi-resonant structure of piezoelectric PVDF films energy harvester (PPEH), which consists of two cantilevers with resonant frequencies of 15Hz and 22Hz. With increased acceleration, the vibration amplitudes of the two cantilever-mass structures are increased and collision occurs which causes strong mechanical coupling between the two subsystems. The experimental results show that the operating bandwidth is widened to 14Hz (14–28Hz) at an acceleration of 9.81m/s2, and the peak output power can be 0.35μW at a relatively low operation frequency of 16Hz. Simulation and experiments with piezoelectric elements show that the energy harvesting device with the bi-resonant structure can generate higher power output than that of the sum of the two separate devices from random vibration sources at low frequency, and hence significantly improves the vibration-to- electricity conversion efficiency by 40–81%.

A structural tailored piezo actuated cantilever shaped 2-DOF resonators for viscosity and density sensing in liquids

Structural tailoring of cantilever shaped two degrees of freedom (2-DOF) resonators for the measurement of liquid viscosity and density is seldom explained. In this paper, a structural tailored 2-DOF cantilever shaped resonators for the determination of viscosity and density of liquids and its performance is investigated. The 2-DOF resonator consists of a trapezoidal shaped driver and absorber mass of identical frequency with a mass disparity. The driver and absorber mass are connected by a strong mechanical coupling unit which forms the 2-DOF trapezoidal cantilever resonant system (2-DOF TCR). The measurement principle is based on tracking the resonant characteristics of 2-DOF TCR system which depends on the viscosity and density of liquids it operates in. The system is evaluated for its performance in liquids of viscosity ranging from 0.23 mPas to 1400 mPas and density ranging from 713kg/m3 to 1261kg/m3. The resonant characteristics are compared with the existing 2-DOF rectangular cantilever resonant system (2-DOF RCR) and 1-DOF rectangular cantilever resonant system (1-DOF RCR) of same length. The theoretical results obtained from this study are in good agreement with the experimental results and the 2-DOF TCR system shows better sensitivity in determining the liquid viscosity and density.

Non-equilibrium tunneling through Au–C20–Au molecular bridge using density functional theory–non-equilibrium Green function approach

Abstract

Late Oligocene–early Miocene submarine volcanism and deep-marine sedimentation in an extensional basin of southern Chile: Implications for the tectonic development of the North Patagonian Andes

The Chilean margin has been used as the model of an ocean-continent convergent system dominated by compression and active mountain building as a consequence of the strong mechanical coupling between the upper and the lower plates. The Andean Cordillera, however, shows evidence of alternating phases of compressional and extensional deformation. Volcano-sedimentary marine strata in the Aysen region of southern Chile contribute to an understanding of the causes of extensional tectonics and crustal thinning that occurred in the Andean orogeny because these deposits constitute the only reliable record of submarine suprasubduction volcanism during the Cenozoic in southern South America. In order to discern the age and tectono-sedimentary setting of these strata, referred to as the Traiguen Formation, we integrated sedimentology, ichnology, petrography, geochemistry, structural geology, foraminiferal micropaleontology, and U-Pb geochronology. Our results indicate that the Traiguen Formation was deposited in a deep-marine extensional basin during the late Oligocene–earliest Miocene. The geochemistry and petrography of the pillow basalts suggest that they formed in a convergent margin on a thinned crust rather than at an oceanic spreading center. We attribute the origin of the Traiguen Basin to a transient period of slab rollback and vigorous asthenospheric wedge circulation that was caused by an increase in trench-normal convergence rate at ca. 26–28 Ma and that resulted in a regional event of extension and widespread volcanism.

Very high cycle fatigue of a high strength steel under sea water corrosion: A strong corrosion and mechanical damage coupling

This paper is focused on the effect of sea water corrosion on the gigacycle fatigue strength of a martensitic–bainitic hot rolled steel R5 used for manufacturing off-shore mooring chains for petroleum platforms in the North Sea. Crack initiation fatigue tests in the regime of 106 to 1010cycles were carried out on smooth specimens under three different environment conditions: (i) without any corrosion (virgin state) in air, (ii) in air after pre-corrosion, and (iii) in-situ corrosion-fatigue under artificial sea water flow. A drastic effect of sea water corrosion was found: the median fatigue strength beyond 108cycles is divided by 5 compared to virgin state specimens. The crack initiation sites were corrosion pits caused by pre-corrosion or created during corrosion-fatigue under sea water flow. Furthermore some sub-surface and internal crack initiations were observed on specimens without any corrosion (virgin state). Crack propagation curves were obtained in mode I in air and under sea water flow. Calculation of the stress intensity factor at the tip of cracks emanating from hemispherical surface pits combined with the Paris–Hertzberg–Mc Clintock crack growth rate model showed that fatigue crack initiation period represents most of the fatigue life in the VHCF regime. Additional original experiments have shown physical evidences that the fatigue strength in the gigacycle regime under sea water flow is mainly governed by the corrosion process with a strong coupling between cyclic loading and corrosion.

Self-biased large magnetoelectric coupling in co-sintered Bi0.5Na0.5TiO3 based piezoelectric and CoFe2O4 based magnetostrictive bilayered composite

In this work, magnetoelectric properties of a co-sintered bilayered composite of non-lead based piezoelectric 0.97(Bi0.5Na0.5TiO3)–0.03(K0.47Na0.47Li0.06Nb0.74Sb0.06Ta0.2O3) and magnetostrictive Co0.6Zn0.4Fe1.7Mn0.3O4 are presented. Similar optimal sintering conditions of the individual components lead to a very clean interface as evidenced in the scanning electron microscopy, angle dispersive X-ray diffraction, and energy-dispersive X-ray (EDX) results. Clean interface results in strong intimate mechanical coupling between both components and causes a maximum transfer of induced strain, leading to a large magnetoelectric coupling ∼142 mV/cm·Oe measured in longitudinally magnetized-transversely polarized configuration (L-T mode). Remnant polarization ∼32 μC/cm2, remnant magnetization ∼0.50 emu/g, and sufficiently high self biased magnetoelectricity ∼135 mV/cm Oe (L-T mode) were observed for this composite.