Magnetoelastic Sensor Research Articles

Improvement of sputtered Galfenol thin films for sensor applications

Galfenol Fe83Ga17 films are sputtered on Si wafers without, and with Ti or Ti/Cu metallic seedlayers in order to obtain a magnetoelastic layer which is sensitive to bendingdeformations of the compound structure. The layer thicknesses range from 100 nm to 5 µm. Layer morphology, texture, and the Villari effect are examined. Thetexture of the Galfenol films is strongly influenced by the seed layer. Nolow-index texture components are found for films directly deposited on Si andSiO2. On Ti, a (111) texture is formed on layers with more than 1000 nm thickness.A favorable (110) fiber texture is formed on Ti/Cu. Deforming the bimorphs (Si + layer system) by 0.012%, the Villari effect is detected due to the change in relativepermeability. The maximum change occurs for Galfenol films with a thickness of 1 µm on a Ti/Cu buffer layer. The films open a route to the incorporation of magnetoelastic filmsinto integrated magnetoelastic sensor devices.

Detection of pathogen Escherichia coli O157:H7 with a wireless magnetoelastic-sensing device amplified by using chitosan-modified magnetic Fe 3O 4 nanoparticles

We report on a wireless magnetoelastic-sensing device for the assay of pathogen with Escherichia coli O157:H7 ( E. coli) as a target using chitosan-modified magnetic Fe 3O 4 nanoparticles (CMNPs) as signal-amplifying tags. At suitable pH the CMNPs, Fe 3O 4 nanoparticles functionalized with a layer of chitosan, bind to negatively charged E. coli through electrostatic attraction. The E. coli attached CMNPs are magnetically bound to the surface of the magnetoelastic sensor, resulting in enhanced mass loading on the sensor surface that in turn decreases its resonance frequency allowing quantification of E. coli concentrations. The sensor shows a linear response to the logarithmic concentration of E. coli in the range of 10 cells mL −1 to 3.7 × 10 8 cells mL −1, with a detection limit (LOD) of 10 cells mL −1. Small molecules such as albumin bovine and ovalbumin show no interference on the detection.

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.

A polymer-Metglas sensor used to detect volatile organic compounds

In this work, the commercial polymer BAYHYDROL-110 has been employed as the analyte-responsive recognition layer on a magnetoelastic sensor used to detect several volatile organic compounds. The sensor exhibits enhanced selectivity to o-xylene and p-xylene compared to six other tested volatile organic compounds as well as to humidity. The sensitivities to o-xylene and p-xylene were −0.27 and −0.19 kHz/ppm of vapor concentration in air, respectively. The sensor exhibits excellent repeatability and stability over a period of at least 75 days, and relatively quick response times (on the order of a minute), but rather low recovery times (in the range of several minutes). The sensor's sensitivity increases linearly with the mass of the polymer, but it is only slightly dependent on the sensor's length.

A Biosensor System for the Detection of Salmonella Typhimurium Using Multiple Phage-based Magnetoelastic Biosensors

AbstractMagnetoelastic (ME) sensors provide a fast, sensitive method to detect bacteria with smaller sensors have higher mass sensitivity for detecting lower concentrations of bacteria. However, signals from smaller sensors are weaker and have more noise due to manufacturing defects. In this paper, we present a biosensor system for the detection of Salmonella typhimurium using multiple magnetoelastic sensors, each with the size of 2000 × 400 × 30 μm. The sensors are immobilized with E2 phage, which specifically binds with S. typhimurium. Unlike traditional methods, our system uses a step pulse to “shock” the sensor, causing it to vibrate at its natural resonance frequency and produce a signal in the pickup coil due to reverse magnetostriction. A Fast Fourier Transform (FFT) was used to determine the resonance frequency. As the biosensor captures S. typhimurium cells, its mass increases with a corresponding decrease of its resonance frequency.The detection system was composed of one coil with a reference sensor to monitor stability, and another coil with three measurement sensors separated in three tubes for simultaneous detection of bacteria. With multi-sensors the effect of a manufacturing defect is decreased and we get the benefit of averaging for more accurate and reliable results. Stability tests show that the variance of frequency detection is less than 122 ppm of its resonance frequency. SEM pictures of the sensor surface show a uniform binding of S. typhimurium cells. Cells were counted and the mass change calculated. The measured frequency change corresponds well to the theoretical change. The results show that the multiple phage based ME biosensors are able to simultaneously detect S. typhimurium and offer good sensitivity and reliability of detection.

Detection of Staphylococcus Aureus in Different Liquid Mediums Using Wireless Magnetoelastic Sensor

Abstract The magnetoelastic Staphylococcus aureus (S. aureus) wireless sensor was fabricated to detect S. aureus in different liquid mediums. Approximately 0.2 mL bacterial solution with proper concentration was taken into testing cuvette containing 2 mL of liquid medium, and the magnetoelastic sensor resonance frequency changed with the growth of bacteria. By changing the concentration of beef extract and peptone, sensor had the most frequency response in culture medium (CM) 2-2 incubated with 2 × 105 cells mL−1 S. aureus. The results indicated that the sensor can be used to determine S. aureus in the concentrations range of 3 × 103–2 × 107 cells mL−1 in CM and 104–107 cells mL−1 in milk, with a detection limit of 103 and 104 cells mL−1, respectively. The sensor frequency shift was correlated to the logarithmic value of the concentration of S. aureus. The coefficient was 0.98 in milk and 0.99 in CM.

Variations in geoacoustic emissions in a deep borehole and its correlation with seismicity

Continuous geoacoustic emission (GAE) measurements were acquired using a three-component geophone placed in a borehole at a depth of near 1000 m at Petropavlovsk-Kamchatsky starting in August 2000. Using geophones consisting of magneto-elastic crystal ferromagnetic sensors, and installed at such a depth allows measurement of natural geoacoustic background with signal amplitude less than 1×10 -4 m/s 3 in frequency band from 3 to 1500 Hz. According to the data from a 4-year survey period the characteristics of diurnal geoacoustic variations change before every earthquake with MLH≥ 5.0 that occurs at a distance of less than 300 km from the observation point or before each earthquake with MLH≥5.5 occurring at distance R≤550 km from the observation point. The changes in GAE regime correlate with the strongest earthquakes that occurred during survey period. Measurements of the natural electromagnetic field of the Earth were carried out simultaneously with the help of an underground electric antenna. The behavior of GAE in aseismic periods appears to be related to the effect of diurnal variations of the natural electromagnetic field.

Design and characterization of a magnetoelastic sensor for the detection of biological agents

This paper presents the design and development of a free-standing, magnetoelastic biosensor. The detection principle is presented and various resonance characteristics of the sensor are discussed. Experimental measurements of the sensor resonance frequencies agree with theoretical predictions. The influence of the external magnetic field on the resonance behaviour of the sensor was studied and the optimum dc magnetic fields for best sensitivity in air and in water solutions for 2000 × 400 × 15 µm (2 mm) sensors and 1000 × 200 × 15 µm (1 mm) size sensors were determined to be 75 Oe and 38 Oe, respectively. Both theoretical prediction and experimental results show that smaller sensors have greater mass sensitivity and can theoretically detect mass as small as one biological spore. The sensor platform was immobilized with JRB7 phages for specific, in vitro detection of B. anthracis spores. Real-time detection of spores suspended in water was demonstrated using a flowing system. The 1 mm and 2 mm sensors were found to have a detection limit of 104 spores ml−1 and 105 spores ml−1, respectively.

Magnetoelastic Strain Sensor for Optimized Assessment of Bone Fracture Fixation

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In orthopedic surgery, measuring the strain in an internal plate over time makes it possible to monitor the bone fracture healing process. Magnetoelastic sensing provides a wireless, highly sensitive, and low-cost technique for measuring strain. An amorphous ribbon is bonded to the implant plate and an emitter/receiver unit is placed outside the patient's body. Bonding the sensor to a plane surface decreases its output signal intensity due to an increase of the magnetic anisotropy. To overcome this problem, we demonstrate a sensor signal detection system, which increases the signal-to-noise ratio. This system is based on a pair of flat miniaturized coils that can be put on the patient's skin. This technology is then applied to measure strain in a plate that supports a fractured generic bone under static loading conditions. The sensor output responses are presented and the high accuracy values obtained are given. </para>

Wireless, remote-query, and high sensitivity Escherichia coli O157:H7 biosensor based on the recognition action of concanavalin A.

Escherichia coli O157:H7 is detected using a remote-query (wireless, passive) magnetoelastic sensor platform to which a 1 microm thick layer of Bayhydrol 110 and then a layer of functionalized mannose is applied. The multivalent binding of lectin concanavalin A (Con A) to the E. coli surface O-antigen and mannose favors the strong adhesion of E. coli to the mannose-modified magnetoelastic sensor; E. coli is rigidly and strongly attached on the mannose-modified sensor through Con A, which works as a bridge to bind E. coli to the mannose-modified sensor surface. As E. coli is bound to the sensor, its resonance frequency shifts, enabling quantification of E. coli concentration with a limit of detection of 60 cells/mL and a linear logarithmic response range of 6.0 x 10(1) to 6.1 x 10(9) cells/mL. The analysis can be directly conducted without incubation and completed in 3 h or less.

Optimization of Magnetoelastic Temperature Sensor Based on Multilayer Microwires

Optimization of Magnetoelastic Temperature Sensor Based on Multilayer Microwires

Differential Magnetoelastic Compressive Force Sensor Utilizing Two Amorphous Alloy Ring Cores

Paper presents the results of investigation on functional characteristics of magnetoelastic compressive force sensor utilizing two Fe81Si4B15 amorphous alloy ring-shaped cores. Uniform distribution of stresses in one of two cores was achieved owing to special non-magnetic backings. Signal from sensing coils of cores was connected to differential amplifier, whereas sine wave voltage signal was applied to magnetizing circuit. High stress sensitivity of developed sensor was indicated together with expected reduction of temperature sensitivity of magnetoelastic sensor. These results confirm, that differential configuration of magnetoelastic sensor is suitable for practical application in sensors development.

Amorphous magnetoelastic sensors for the detection of biological agents

Freestanding amorphous magnetoelastic (ME) biosensors were fabricated by two ways. One type with larger size, 2000 × 400 × 15 μm, 1000 × 200 × 15 μm and 500 × 100 × 15 μm, was made from an ME Fe40Ni38Mo4B18 ribbon, the other with smaller size 200 × 40 × 4 μm was manufactured by dual beam sputtering and non-traditional microelectronic fabrication techniques. Both platforms were immobilized with JRB7 phage and were developed for the real-time in vitro detection of Bacillus anthracis spores. The experimental results show that the measured sensitivity of the ME sensors agrees with theoretical predictions and the specificity of ME sensors coated with JRB7 phage for B. anthracis spore species is excellent. The 200 × 40 × 4 μm biosensor was found to have a detection limit of 10 2 cfu/ml and sensitivity of 13.1 kHz/decade.

On Mass Loading and Dissipation Measured with Acoustic Wave Sensors: A Review

We summarize current trends in the analysis of physical properties (surface mass density, viscosity, elasticity, friction, and charge) of various thin films measured with a solid‐state sensor oscillating in a gaseous or liquid environment. We cover three different types of mechanically oscillating sensors: the quartz crystal microbalance with dissipation (QCM‐D) monitoring, surface acoustic wave (SAW), resonators and magnetoelastic sensors (MESs). The fourth class of novel acoustic wave (AW) mass sensors, namely thin‐film bulk acoustic resonators (TFBARs) on vibrating membranes is discussed in brief. The paper contains a survey of theoretical results and practical applications of the sensors and includes a comprehensive bibliography.

Magnetoacoustic sensor system and associated method for sensing environmental conditions

A remote sensor system (60) and method for passively sensing environmental conditions, such as temperature and humidity, uses a magnetic impulse from an AC interrogation coil (68) to stimulate a magnetoelastic sensor (62) to generate an acoustic signal (AE) at the resonant frequency of the magnetoelastic sensor (62). The acoustic signal (AE) is received by amplifier (74), detected and displayed (76). The systems and methods are particularly suited for detecting environmental conditions in commercial pharmaceutical packaging, such as blister packs.

Magneto-mechanical impedance of metallic structures

Impedance measurements with a magneto-elastic active sensor are explored for inferring the magneto-mechanical impedance (MMI) of a metallic structure. It is shown that the MMI contains electrical response of the sensor and both electrical and mechanical structural responses. An analytical model is suggested that accounts for electrical characteristics of the sensor, sensor/structure electromagnetic interaction, and multimodal structural dynamic behavior. The model is validated with a set of MMI experiments demonstrating feasibility of deducing structural natural frequencies and structural vibration modes.

Determination of glucose using bienzyme layered assembly magnetoelastic sensing device

A bienzyme layered assembly on magnetoelastic sensor, consisting of horseradish peroxidase and glucose oxidase is used to sense glucose by the horseradish peroxidase-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine, by H 2O 2, and the formation of the insoluble product on the sensor surface. A horseradish peroxidase is used to analyze hydrogen peroxide (H 2O 2) via the biocatalyzed oxidation of tetramethylbenzidine and the precipitation of the insoluble product. The glucose oxidase catalyzed oxidation of glucose produces gluconic acid and H 2O 2, and the generated H 2O 2 effects the formation of the insoluble product in the presence of horseradish peroxidase. The insoluble product accumulated on the sensor surface resulting in shifts of the sensor resonance frequency which are correlated with the amount of H 2O 2 or glucose. The biosensor response is linear in the range of glucose concentrations of 5–50 mM, with a detection limit of 2 mM at a noise level of ∼10 Hz. The biosensor is applied to determine glucose concentration in urine sample.

Dual-cathode method for sputtering magnetoelastic iron-boron films

Magnetoelastic sensors have gained attention in recent years due to their wireless nature and versatility in sensing applications, but there have been issues with fabrication, especially as sensor platform sizes approach the microscale. In this work, a dual-cathode method is presented for the co-deposition of iron and boron to produce magnetoelastic films that serve as the basis for wireless sensors. Deposition rate and film composition experiments were performed to optimize sputtering conditions for obtaining high-quality films with compositions near to the goal of 80/20 at.% iron/boron. The magnetoelasticity of films produced using this method, along with the potential of wireless sensors based upon these films, was confirmed by fabricating small (500 × 100 × 5 μm) sensor platforms and then testing for resonance using a coil and a network analyzer. These sensors were found to have resonance frequencies of around 4 kHz with Q-values, in air, of over 1000. By coating the sensor platforms with gold using a third cathode, and then annealing in a vacuum oven at 220 °C, the environmentally sensitive iron-based alloy that forms the core of the sensor platform may be protected from corrosion.

Monitoring of Mycoplasma genitalium growth and evaluation of antibacterial activity of antibiotics tetracycline and levofloxacin using a wireless magnetoelastic sensor

Mycoplasma genitalium (Mg) is the smallest and simplest self-replicating bacteria lacking of cell wall and is a human pathogen causing various diseases. This paper describes the real-time, long-term and in situ monitoring of the growth of Mg and evaluation of the effect of the antibiotics tetracycline and levofloxacin on the growth using a wireless magnetoelastic sensor. The sensor is fabricated by coating a magnetoelastic strip with a polyurethane protecting film. In response to a time-varying magnetic field, the sensor longitudinally vibrates at a resonance frequency, emitting magnetic flux that can be remotely detected by a pick-up coil. No physical connections between the sensor and the detection system are required. The wireless property facilitates aseptic operation. The adhesion of Mg on the sensor surface results in a decrease in the resonance frequency, which is proportional to the concentration of Mg. The shift of the resonance frequency–time curves shows that under routine culture condition the growth curve of Mg is composed of three phases those are lag, logarithmic and stationary phase, respectively. In the presence of the antibiotics, the lag phase in the growth inhibition curves is prolonged obviously and the stationary phase is substituted by a decline phase. The growth inhibition of Mg is related to the concentration of the antibiotics. The MIC50 (minimal inhibitory concentration) of Mg incubated in the presence of the antibiotics for 120h is calculated to be 1.5 and 0.5μg/mL for tetracycline and levofloxacin, respectively.

Microfabricated Magnetoelastic Biosensors for the Detection of Bacillus Anthracis Spores

Phage based magnetoelastic biosensors for wireless detection of Bacillus anthracis spores were fabricated. The biosensor is composed of a magnetoelastic resonator platform, and JRB7 phage, a genetically engineered bacteriophage that specifically binds with Bacillus anthracis spores, as the bio-molecular recognition element. The phage was engineered at Auburn University and immobilized onto all surfaces of the sensors. To achieve high sensitivity, micro-scale magnetoelastic particle sensor platforms were manufactured using microelectronics fabrication techniques. Real-time in liquid tests were conducted to determine the sensitivity and detection limit of the biosensors by exposing the biosensors to static solutions containing known concentrations of spores. Experimental results showed that the biosensor has a detection limit of approximately 100 spores per ml of liquid and sensitivity of 13 KHz per decade for the detection of Bacillus anthracis spores. Additionally, the phage based biosensors showed high binding affinity and specificity, and superior stability compared with antibody based biosensors.