Magnetoelastic Ribbon Research Articles

Optimizing Contact-Less Magnetoelastic Sensor Design for Detecting Substances Accumulating in Constrained Environments

The optimization of a contact-less magnetoelastic sensing setup designed to detect substances/agents accumulating in its environment is presented. The setup is intended as a custom-built, low-cost yet effective magnetoelastic sensor for pest/bug detection in constrained places (small museums, labs, etc.). It involves a short, thin, and flexible polymer slab in a cantilever arrangement, with a short Metglas® 2826 MB magnetoelastic ribbon attached on part of its surface. A mobile phone both supports and supplies low-amplitude vibration to the slab’s free end. When vibrating, the magnetoelastic ribbon generates variable magnetic flux, thus inducing voltage in a contact-less manner into a pick-up coil suspended above the ribbon. This voltage carries specific characteristic frequencies of the slab’s vibration. If substances/agents accumulate on parts of the (suitably coated) slab surface, its mass distribution and, hence, characteristic frequencies change. Then, simply monitoring shifts of such frequencies in the recorded voltage enables the detection of accumulating substances/agents. The current work uses extensive testing via various vibration profiles and load positions on the slab, for statistically evaluating the sensitivity of the mass detection of the setup. It is shown that, although this custom-built substance/agent detector involves limited (low-cost) hardware and a simplified design, it achieves promising results with respect to its cost.

The Effect of the Thermal Annealing Process to the Sensing Performance of Magnetoelastic Ribbon Materials

The magnetoelastic materials find many practical applications in everyday life like transformer cores, anti-theft tags, and sensors. The sensors should be very sensitive so as to be able to detect minute quantities of miscellaneous environmental parameters, which are very critical for sustainability such as pollution, air quality, corrosion, etc. Concerning the sensing sensitivity, the magnetoelastic material can be improved, even after its production, by either thermal annealing, as this method relaxes the internal stresses caused during manufacturing, or by applying an external DC magnetic bias field during the sensing operation. In the current work, we performed a systematic study on the optimum thermal annealing parameters of magnetoelastic materials and the Metglas alloy 2826 MB3 in particular. The study showed that a 100% signal enhancement can be achieved, without the presence of the bias field, just by annealing between 350 and 450 °C for at least half an hour. A smaller signal enhancement of 15% can be achieved with a bias field but only at much lower temperatures of 450 °C for a shorter time of 20 min. The magnetic hysteresis measurements show that during the annealing process, the material reorganizes itself, changing both its anisotropy energy and magnetostatic energy but in such a way such that the total material energy is approximately conserved.

A bovine serum albumin-coated magnetoelastic biosensor for the wireless detection of heavy metal ions

A magnetoelastic (ME) biosensor functionalized by bovine serum albumin (BSA) was firstly developed for the wireless detection of heavy metal ions in solution. The biosensor was fabricated by coating a gold-modified ME ribbon with BSA. Its resonance oscillation and resonance frequency can be actuated and wirelessly monitored through magnetic fields. The combination of heavy metal ions and BSA produces the precipitation adhered to the biosensor surface, resulting in the increase of mass loading, and consequently leads to a decrease in the resonance frequency, corresponding to the concentrations of heavy metal ions. The biosensor was used to separately detect Pb2+, Cd2+ and Cu2+. Its response is linearly proportional to the low concentrations, becoming sub-linear at higher concentrations. Moreover, the SEM, fluorescence microscopy and EDS spectrum analysis proved that the modification and detection process were successful. The biosensor is more sensitive to the heavy metal with larger molecular weight, and has the sensitivity for Pb2+, Cd2+ and Cu2+ of about 9.4×107Hz per mol/L, 7.1×107Hz per mol/L and 4.7×107Hz per mol/L, respectively. The detection limits for Pb2+ and Cd2+ of 3.3×10−7mol/L and 2.4×10−7mol/L, respectively, are lower than the standard limit (GB 8978-1996).

Nanostructured ZnO in a Metglas/ZnO/Hemoglobin Modified Electrode to Detect the Oxidation of the Hemoglobin Simultaneously by Cyclic Voltammetry and Magnetoelastic Resonance.

In the present work, a nanostructured ZnO layer was synthesized onto a Metglas magnetoelastic ribbon to immobilize hemoglobin (Hb) on it and study the Hb’s electrochemical behavior towards hydrogen peroxide. Hb oxidation by H2O2 was monitored simultaneously by two different techniques: Cyclic Voltammetry (CV) and Magnetoelastic Resonance (MR). The Metglas/ZnO/Hb system was simultaneously used as a working electrode for the CV scans and as a magnetoelastic sensor excited by external coils, which drive it to resonance and interrogate it. The ZnO nanoparticles for the ZnO layer were grown hydrothermally and fully characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and photoluminescence (PL). Additionally, the ZnO layer’s elastic modulus was measured using a new method, which makes use of the Metglas substrate. For the detection experiments, the electrochemical cell was performed with a glass vial, where the three electrodes (working, counter and reference) were immersed into PBS (Phosphate Buffer Solution) solution and small H2O2 drops were added, one at a time. CV scans were taken every 30 s and 5 min after the addition of each drop and meanwhile a magnetoelastic measurement was taken by the external coils. The CV plots reveal direct electrochemical behavior of Hb and display good electrocatalytic response to the reduction of H2O2. The measured catalysis currents increase linearly with the H2O2 concentration in a wide range of 25–350 μM with a correlation coefficient 0.99. The detection limit is 25–50 μM. Moreover, the Metglas/ZnO/Hb electrode displays rapid response (30 s) to H2O2, and exhibits good stability and reproducibility of the measurements. On the other hand, the magnetoelastic measurements show a small linear mass increase versus the H2O2 concentration with a slope of 152 ng/μM, which is probably due to H2O2 adsorption in ZnO during the electrochemical reaction. No such effects were detected during the control experiment when only PBS solution was present for a long time.

Preparation and characterisation of a sensing system for wireless pH measurements in vivo, in a rumen of a cow

We describe a sensing system that is able to measure pH in-vivo, in the rumen of a cow, in real time. The sensing principle is based on gravimetric transduction using a magnetoelastic ribbon functionalized by pH-sensitive nanobeads that is placed in the rumen where it is actuated and read-out wirelessly. We describe a generic procedure that enables one to deposit monolayers or multilayers of nano- and micro beads onto virtually any substrate. The topography of the resulting layers as well as interlayer coverages were characterised using optical microscopy and scanning profilometry. First we determined performance of the system in-vitro, in phosphate-buffered saline, in McDougall’s buffer and in a rumen fluid. Thereafter we also performed in-vivo measurements.Using buffers we determined pH response in the liquids both at the fundamental frequency of the functionalised foils, and at the 1st overtone. We argue that observed frequency changes vs pH are mainly due to changes of trapped liquid when the bead layers shrink or expand as a response to changed pH. The data obtained from the pH response of magnetoelastic foils at different bead coverages was modelled by a simple two-parameter model that corroborates this assumption.

The use of a non-linear model for a more realistic calculation of the “[formula omitted] effect” in magnetoelastic ribbons

In the current paper an exact analytic expression in a closed form is given for the impedance Z of a finite size coil having as a core a magnetoelastic thin ribbon along its axis. From the impedance formula, the resonance and anti-resonance frequencies fR and fA are calculated and their ratio is related to the “ΔE effect” of the magnetoelastic materials. This is of great importance for these materials because the “ΔE effect” reveals information about their internal structure and also the resonance and anti-resonance frequencies are relatively easy to measure. Our analysis is more realistic than previous attempts to do similar calculations which overestimate the anti-resonance frequency because a) a more accurate non-linear model is used in the current work to describe the magnetic behavior of the magnetoelastic thin ribbon, and b) finite size coils are assumed as is the case in real experiments. The results show that even though fR depends on the “ΔE effect” and ribbon properties (material and geometry), fA depends additionally on the geometry of the excitation coil.

Radiofrequency magnetoelastic resonators for magnetoelectric applications

Magnetoelastic resonance measurements are carried out in short ribbons (down to 1 cm length) of Fe59Co16Si15B10 metallic glasses, both as-quenched and after annealing at 400 °C for 10 min. The resonant frequency exceeds 200 kHz with good Q factors for the shortest elements in the as-quenched state. Sandwich-type laminated magnetoelectric (ME) composites are prepared by gluing these ribbons to a PVDF piezoelectric polymer layer, showing good ME response. This effect is discussed as a function of the as-quenched or annealed state, and the length of the magnetoelastic ribbon, and is of interest for near field communication applications.

Zeolite micromembrane fabrication on magnetoelastic material using electron beam lithography

In the present study, electron beam lithography (EBL) is employed in the manufacturing of patterns of continuous Linde Type A (LTA) zeolite membranes. The patterns are down to the micrometer scale and they are composed of LTA micromembranes having all three dimensions in the micrometer scale. The control of the size and location of zeolite films or membranes onto specific substrates, will lead to new aspects for their use in microsensing, microelectronics and microreactor applications. Our focus is on the microsensing field, where a magnetoelastic ribbon (Metglas) is used as the sensing platform, since the Metglas/zeolite film composite has been successfully used for the detection of gases and VOCs in the past. Here we report on the first LTA zeolite micromembrane attached onto a previously EBL patterned PMMA coated Metglas substrate. The sensing ability of such a sensor could be significantly improved by using lower amount of zeolite film since it could lead to shorter response and recovery times. The conditions for the manufacturing of the LTA micromembranes onto the Metglas substrate are investigated and discussed in terms of EBL, seeding and hydrothermal synthesis parameters.

A wireless and sensitive detection of octachlorostyrene using modified AuNPs as signal-amplifying tags

A wireless, remote query octachlorostyrene (OCS) biosensor was fabricated by coating a mass-sensitive magnetoelastic ribbon with anti-OCS antibody. In response to a time-varying magnetic field, the magnetoelastic sensor mechanically vibrates at a characteristic resonance frequency which inversely depends on the sensor mass loading. As the magnetoelastic film is magnetostrictive itself, the vibrations launch magnetic flux that can be remotely detected using a pickup coil. Au nanoparticles (NPs) were used to amplify the mass loading. In a sample solution containing OCS target and OCS-modified AuNPs (OCS–AuNPs), both OCS and OCS–AuNPs react with the anti-OCS antibody immobilized on the sensor surface in a competition mode. The bound OCS–AuNPs amount is inversely proportional to the OCS target concentration. The reduction of bound OCS–AuNPs induced by free OCS results in significant change in mass loading, which amplifies the responses. The biosensor demonstrates a linear shift in resonance frequency with OCS concentration between 7.4μM and 9nM, with a detection limit of 2.8nM.

A new method for measuring the adsorption induced stresses of zeolite films using magnetoelastic sensors

A new method is presented for measuring the stresses imposed on a substrate from a zeolite membrane either due to the synthesis of the zeolite film or due to adsorption induced strains. The resonance and anti-resonance frequencies of a zeolite/Metglas ribbon were measured and were related to the stress imposed on Metglas using the phenomenological theory of magnetoelasticity. The adsorption of water in FAU and LTA films were selected as representative systems to be studied. For both zeolite membranes, the stress had a non monotonic dependence (passed through a minimum) on water loading. The measured stresses are in qualitative agreement with the literature data about changes of the zeolite unit cell size as a function of humidity. The developed methodology is general and it can be used for measuring strains due to adsorption in any microporous film as long as it can be deposited as uniform layer on a magnetoelastic ribbon.

In situ and ex vivo evaluation of a wireless magnetoelastic biliary stent monitoring system

This paper presents the in situ and ex vivo evaluation of a system that wirelessly monitors the accumulation of intimal tissue and sludge in a biliary stent. The sensing element, located within the stent, is a magnetoelastic resonator that is queried by a wireless radio frequency signal. The in situ testing uses a commercially-available self-expanding biliary stent enhanced with a 1 mm x 25 mm magnetoelastic ribbon sensor (formed from Metglas 2605SA1). The stent has a conformal magnetic layer (consisting of strontium ferrite particles suspended in polydimethylsiloxane) that biases the sensor. The external interrogation module is able to acquire a signal from the sensor from a distance of at least 5 cm while the sensor is implanted in a porcine carcass and loaded with biological fluids. The ex vivo testing uses bile harvested from the porcine carcass. The response of a 1 mm x 25 mm magnetoelastic ribbon sensor is first calibrated with fluids of known density and viscosity, and the calibrated sensor is used to estimate that the viscosity of the harvested bile is 2.7-3.7 cP. The test results presented in this paper illustrate the fundamental usability of the system when the sensor is implanted, loaded by biological fluids, and interrogated in a surgical setup.

Self-Oscillation Type Wireless Viscosity Sensor Made of Cantilever Type Magnetoelastic Ribbon

This paper describes self-oscillators composed of cantilever type magnetoelastic ribbon resonators as a wireless viscosity sensor. We examined relationship between the viscosity and oscillation amplitude for various mixtures of water and glycerin. The viscosity of 0.314 P could be detected by dipping the edge of the cantilever type resonator into the mixtures. Consequently, we confirmed that a cantilever type ribbon resonator is suitable for measuring viscosity of the high viscosity liquid.

Selective sensor utilizing a thin monolayer of b-oriented silicalite-1 crystals–magneto-elastic ribbon assembly

This report presents the development of new selective gas sensors utilizing a b-oriented silicalite-1 layer-magneto-elastic ribbon assembly. The key principle for the operation of these sensors is monitoring the changes in the resonance frequency of the Metglas strip in relation to the concentration of a component in the gas phase. This technique provides a simple way for monitoring the effects of the amount of adsorbed gases in the silicalite-1 coating. The thickness of the zeolite layer is that of a single crystal. The silicalite-1 crystals are oriented in the b-direction, meaning that the straight channels are perpendicular to the sensor surface, which is confirmed by X-ray diffraction (XRD) analysis. The sensor was able to repeatedly sense carbon dioxide in air and could discriminate between linear and branched hydrocarbons. The sensor was able to detect n-butane, while it did not respond to the presence of iso-butane, indicating sensing selectivity.

The detection of Mycobacterium tuberculosis in sputum sample based on a wireless magnetoelastic-sensing device

This paper presents a real-time detection of Mycobacterium tuberculosis ( M. TB) using a wireless magnetoelastic sensor. The sensor is fabricated by coating a magnetoelastic ribbon (Metglas 2826MB™) with a polyurethane protecting film. M. TB consumes the nutrients of a liquid culture medium in growing and reproducing process, which results in properties changes (viscosity, density, elasticity, ion concentration, etc.) of the culture medium, and consequently changes in the resonance frequency of the magnetoelastic sensor. Using the described technique M. TB is quantified and sensor response is proportional to logarithmic values of the M. TB concentration from 10 4 to 10 9 cells ml −1, with a detection limit of 10 4 cells ml −1 at a noise level of ∼10 Hz. The sensor can be used effectively for monitoring the bacterial growth and good results were obtained when used in sputum sample. The drug-resistance of isoniazid (INH) and rifampin (RFP) on M. TB growth in culture medium was evaluated based on this proposed method. The wireless nature of the presented device facilitates the aseptic operations.

Detection of Pseudomonas aeruginosa using a wireless magnetoelastic sensing device

This paper describes the real-time quantification of Pseudomonas aeruginosa ( P. aeru) concentrations using a wireless magnetoelastic sensing device. The sensor is fabricated by coating a magnetoelastic ribbon with a polyurethane protecting film. In response to an externally applied time varying magnetic field, the magnetoelastic sensor vibrates at a resonance frequency that can be remotely determined by monitoring the magnetic flux emitted by the sensor. The resonance frequency changes in response to properties changes of a liquid culture medium and bacteria adhesion to the sensor as P. aeru consumes nutrients from the culture medium in growth and reproduction. The effects of properties (conductivity, viscosity, mass) are investigated with quartz crystal microbalance (QCM), microscopy imaging, and conductivity measurement. Using the described technique we are able to directly quantify P. aeru concentrations of 10 3 to 10 8 cells/ml, with a detection limit of 10 3 cells/ml at a noise level of ∼20 Hz. The lack of any physical connections between the sensor and the monitoring electronics facilitates aseptic operation, and makes the sensor platform ideally suited for monitoring bacteria from within, for example, sealed food containers.

A Wireless pH Sensor Using Magnetoelasticity for Measurement of Body Fluid Acidity

The determination of body fluid acidity using a wireless magnetoelastic pH-sensitive sensor is described. The sensor was fabricated by casting a layer of pH-sensitive polymer on a magnetoelastic ribbon. In response to an externally applied time-varying magnetic field, the magnetoelastic sensor mechanically vibrates at a characteristic frequency that is inversely dependent upon the mass of the pH polymer film, which varies as the film swells and shrinks in response to pH. As the magnetoelastic sensor is magnetostrictive, the mechanical vibrations of the sensor launch magnetic flux that can be detected remotely using a pickup coil. The sensor can be used for direct measurements of body fluid acidity without a pretreatment of the sample by using a filtration membrane. A reversible and linear response was obtained between pH 5.0 and 8.0 with a measurement resolution of pH 0.1 and a slope of 0.2 kHz pH(-1). Since there are no physical connections between the sensor and the instrument, the sensor can be applied to in vivo and in situ monitoring of the physiological pH and its fluctuations.

Acid Phosphatase Assay with a Wireless Magnetoelastic Biosensor

A wireless remote‐query disposable magnetoelastic (ME) biosensor was developed for the assay of acid phosphatase (ACP). The sensor was fabricated by applying a magnetoelastic ribbon with a layer of pH‐sensitive polymer and upon it a sensing film containing bovine serum albumin (BSA) and adenosine‐5′‐monophosphate (5′‐AMP). The ACP‐catalyzed hydrolysis of 5′‐AMP decreases the solution pH, resulting in the polymer shrinking and consequently the resonance frequency of the magnetoelastic sensor increasing. The kinetic parameters were measured to be 1.64×10−3 M (Michaelis constant) and 130 Hz/min (maximum initial rate). The proposed sensor can determine 0.2 to 1.2 U/ml of ACP.

Acid Phosphatase Assay with a Wireless Magnetoelastic Biosensor

A wireless remote‐query disposable magnetoelastic biosensor is developed for the assay of acid phosphatase (ACP). The sensor was fabricated by applying a layer of pH‐sensitive polymer to a magnetoelastic ribbon and, on top of it, a sensing film containing bovine serum albumin and adenosine‐5′‐monophosphate (5′‐AMP), the substrate of ACP. In response to an externally applied time‐varying magnetic field, the magnetoelastic sensor mechanically vibrates at a characteristic frequency that is inversely dependent on the mass of the attached film. Because the magnetoelastic sensor is magnetostrictive, the mechanical vibrations of the sensor launch magnetic flux that can be detected remotely from the sensor using a pick‐up coil. The ACP‐catalyzed hydrolysis of 5′‐AMP decreases the solution pH, resulting in the polymer shrinking and, consequently, the resonance frequency of the magnetoelastic sensor increasing. The experimental condition was optimized to be 37°C, in 2.5 mM sodium citrate buffer solution (pH 6.5). Using citrate as buffer can enhance the ACP activity, partly offsetting the effect of the buffer capacity on the sensitivity. The kinetic parameter were measured to be: 1.64×10–3 M (Michaelis constant) and 130 Hz/min (maximum initial rate). This work provides a remote enzymatic assay of ACP. The relative standard deviation in the measurements of six sensors in parallel is 3.4%. The proposed sensor can determine 0.2∼1.2 U/ml of ACP.

磁性リボンを用いた自励式発振器小型リモート粘度·密度センサへの適用

磁性リボンを用いた自励式発振器小型リモート粘度·密度センサへの適用

A 2826 MB Metglas ribbon as a strain sensor for remote and dynamic mechanical measurements

A 2826 Metglas magnetoelastic ribbon was used as a sensor for remote, dynamic, and passive strain measurements, using a detection coil. The ribbon was attached to an epoxy resin slab and the system was dynamically loaded by a dynamic mechanical analysis (DMA) system at various loading frequencies. There was a strong correlation between the DMA data and the voltage data from the detection coil. Displacements, as low as 20 μm were easily detected and the gauge factor, which increased with the DMA frequency, was found equal to 11,700 at the 150 Hz frequency.