Magnetoelastic Research Articles

An Advanced Magnetoelastic (ME) Sensing of Salmonella By the Improvement of Pathogen Recovery Rate Using Tween20 Modified Swabs

Swabbing, as an inexpensive, easy-to-use, and widely accepted sampling method, has been used to help magnetoelastic (ME) biosensing system for the surface pathogen quick detection. This paper introduced a modification method using a surfactant, Tween20, to help to improve the recovery rate of different swabs. In our previous research, swabbing substituted the direct ME sensor detection on the sample surfaces, which improved the detection area of one sensor from 0.2X1 mm2 into 30X30 mm2. This amendment altered the former surface spot measurement into a large area measurement. To improve the accuracy of this swabbing technique to a better level, a higher recovery rate is needed. Tween20, a stable and relatively non-toxic surfactant, was employed to modify the fibers of swabs so that after the pathogens are picked up, they would be easier to be released into DI water and detected by ME sensors. In this research, traditional swabs, such as cotton-tipped, rayon-tipped, and novel flocked swabs are used for comparison.

Control of cellular adhesion and myofibroblastic character with sub-micrometer magnetoelastic vibrations

The effect of sub-cellular mechanical loads on the behavior of fibroblasts was investigated using magnetoelastic (ME) materials, a type of material that produces mechanical vibrations when exposed to an external magnetic AC field. The integration of this functionality into implant surfaces could mitigate excessive fibrotic responses to many biomedical devices. By changing the profiles of the AC magnetic field, the amplitude, duration, and period of the applied vibrations was altered to understand the effect of each parameter on cell behavior. Results indicate fibroblast adhesion depends on the magnitude and total number of applied vibrations, and reductions in proliferative activity, cell spreading, and the expression of myofibroblastic markers occur in response to the vibrations induced by the ME materials. These findings suggest that the subcellular amplitude mechanical loads produced by ME materials could potentially remotely modulate myofibroblastic activity and limit undesirable fibrotic development.

"Electro Magneto Elastic Actuator for Nanotechnology and Biotechnology"

"Electro Magneto Elastic Actuator for Nanotechnology and Biotechnology"

A magnetoelastic biosensor based on E2 glycoprotein for wireless detection of classical swine fever virus E2 antibody

A wireless magnetoelastic (ME) biosensor immobilized with E2 glycoprotein was first developed to detect classical swine fever virus (CSFV) E2 antibody. The detection principle is that a sandwich complex of CSFV E2 – rabbit anti-CSFV E2 antibody – alkaline phosphatase (AP) conjugated goat anti-rabbit IgG formed on the ME sensor surface, with biocatalytic precipitation used to amplify the mass change of antigen–antibody specific binding reaction, induces a significant change in resonance frequency of the biosensor. Due to its magnetostrictive feature, the resonance vibrations and resonance frequency can be actuated and wirelessly monitored through magnetic fields. The experimental results show that resonance frequency shift increases with the augmentation of the CSFV E2 antibody concentration. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and fluorescence microscopy analysis proved that the modification and detection process were successful. The biosensor shows a linear response to the logarithm of CSFV E2 antibody concentrations ranging from 5 ng/mL to 10 μg/mL, with a detection limit (LOD) of 2.466 ng/mL and the sensitivity of 56.2 Hz/μg·mL−1. The study provides a low-cost yet highly-sensitive and wireless method for selective detection of CSFV E2 antibody.

Detection of Salmonella Enterica with Magnetoelastic Biosensors in Wash Water Containing Clorox and Chlorine Dioxide

Magnetoelastic (ME) biosensors with phage-displayed oligopeptide probes have been demonstrated to be highly successful in rapid detection of various pathogens, including Salmonella enterica, on the fruit and vegetable surfaces. However, in lieu of testing each produce individually, it is advantageous to detect pathogens in the produce wash water for high-throughput analysis. The sanitizing guidelines of the United States Food and Drug Administration (FDA) suggest adding Clorox and chlorine dioxide to the produce wash water in processing plants to disinfect harmful food-borne pathogens on fruit and vegetable surfaces. Therefore, to determine the efficacy of our ME biosensors in testing for food-borne pathogens in produce wash water, we assessed the stability of our biosensors in the presence of Clorox and chlorine dioxide. Specifically, Enzyme Linked Immunosorbent Assay (ELISA) was used to study the potential effect of Clorox and chlorine dioxide on the S. Typhimurium capturing ability of our phage probe. At concentrations recommended by the FDA for Clorox (100 ppm free chlorine content) and by the United States Environmental Protection Agency for chlorine dioxide (4 ppm), we observed no negative effect of these chemicals on the stability and S. Typhimurium capturing ability of our phage-displayed oligopeptide probe. These data demonstrate the potential efficacy of using our ME biosensors with phage-displayed oligopeptide probes in produce wash waters to determine the presence of food-borne pathogens.

Effects of Surface-Scanning Detector Position on the Response of a Wireless Magnetoelastic Biosensor

This paper investigates the measurement accuracy of a wireless magnetoelastic (ME) biosensor for direct pathogen detection on solid surfaces. The experiments were conducted on the surface of a polyethylene (PE) plate as a model study. An ME biosensor (1mm × 0.2 mm × 30 μm) was placed on the PE surface, and a surface-scanning detector was positioned in the proximity of the sensor for wireless resonant frequency measurement. The detector position was accurately controlled by using a motorized three-axis translation system. The results showed that the resonant frequency variations of the sensor were 125 to +150 Hz for X and Y detector displacements of ± 600 μm and Z displacements of +100 to +500 μm. These resonant frequency variations were small compared to the sensor's initial resonant frequency (< 0.007% of 2.2 MHz initial resonant frequency) measured at the detector home position, indicating high accuracy of the measurement.

Bio-Molecular Filter for the Capture of Bacterial Pathogens in Liquid Streams

This paper investigates a bio-molecular filter that enables the evaluation of large volumes of liquid streams for the presence of small quantities of bacterial pathogens. The filter is constructed of a planar arrangement of strip-shaped, bio-receptor immobilized magnetoelastic (ME) biosensors. The ME biosensors are made of a ferromagnetic alloy and coupled to a support frame of the filter by a magnetic force to form a filter plane, through which a liquid of interest flows. The bio-molecular filter is designed to capture specific bacterial pathogens and allow non-specific debris to pass, eliminating a clogging issue. In this work, the construction and working principle of the filter are presented. For a proof-in-concept, two Salmonella-specific bio-receptors, E2 phage and an antibody, were used to capture Salmonella Typhimurium in a large volume of flowing deionized water. The capture efficiency results using the two bio-receptors are compared and discussed.

Enhancement in the Capture Efficiency of Magnetoelastic Biosensors for Salmonella Using a Dilution Method

This paper investigates three different washing methods to improve the capture efficiency of E2 phage-coated magnetoelastic (ME) biosensors for Salmonella Typhimurium. ME biosensors with pre-determined resonant frequencies were exposed to Salmonella Typhimurium of 5x104 cfu/ml for 1 hr. E2 phage immobilized on the biosensors was responsible for specifically capturing the bacteria. After this capture step, the biosensors were washed using three different washing methods, pipette washing, magnetic bar washing, and dilution washing. The dilution method was found to result in the highest capture efficiency of the bacteria and greatest resonant frequency shift of the sensors, which means the lowest loss rate of Salmonella Typhimurium.

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).

Real-Time Bacterial Detection in Liquid By Using Magnetoelastic Biosensors and a Surface-Scanning Coil Detector

Foodborne illness is a common public health problem because food can be contaminated with pathogens at any point in the farm-to-table continuum. This paper presents a rapid method of detecting foodborne bacteria in a small volume of liquid (1 ml) using magnetoelastic (ME) biosensors and a surface-scanning coil detector. The ME biosensors are mass-sensitive, strip-shaped magnetic particles (1 mm × 0.2 mm × 0.03 mm). Phage was coated on the surface of the biosensors to capture a specific pathogen. The resonant frequency of the biosensors decreases when the specific pathogen is attached to the sensor surface. This decrease in resonant frequency was measured in real time by using a surface-scanning coil detector connected to a network analyzer. In this work, the detection device was comprised of the surface-scanning coil detector and glass capillary tubes with two different diameters (0.5 mm and 0.3 mm). The two capillary tubes were nested each other (i.e., the 3 mm tube inserted into the 5 mm tube) to form a flow channel through which a 1 ml bacteria solution was passed. An ME biosensor was placed inside the flow channel through the 0.5 mm tube and positioned where it meets the tip of the 3 mm tube. The 3 mm tube tip served as a stopper to fix the biosensor position in a liquid stream. The surface-scanning detector was positioned under the biosensor for real-time resonant frequency measurement. The flow channel and surface-scanning detector were embedded and fixed in polydimethylsiloxane (PDMS) to ensure the mechanical stability of the entire device. In order to control and change the flow rate of the bacteria solution, a peristatic pump was used to deliver the solution into the flow channel. The E2 phage was used to specifically capture Salmonella Typhimurium cells in a 1 ml concentrated solution passing through the flow channel. The concentration of Salmonella solutions ranged from 103 cfu/ml to 108 cfu/ml. ME biosensors without E2 phage were used as control sensors, and ones coated with E2 phage were used as measurement sensors. Both groups of sensors were tested by passing the Salmonella solutions, and changes in the resonant frequency of the sensors were recorded. The resonant frequency of the measurement sensors were found to decrease, resulting from specific binding of Salmonella on the biosensors. In addition, the resonant frequency shifts of the measurement sensors were much larger than those of the control sensors for the whole tested range of Salmonella concentrations. The presented method can be combined with surface-sampling of bacterial pathogens by swabbing and used for real-time pathogen detection.

Detection of Salmonella Enterica with Magnetoelastic Biosensors in Wash Water Containing Clorox and Chlorine Dioxide

Magnetoelastic (ME) biosensors with phage-displayed oligopeptide probes have been demonstrated to be highly successful in rapid detection of various pathogens, including Salmonella enterica, on the fruit and vegetable surfaces. However, in lieu of testing each produce individually, it is advantageous to detect pathogens in the produce wash water for high-throughput analysis. The sanitizing guidelines of the United States Food and Drug Administration (FDA) suggest adding Clorox and chlorine dioxide to the produce wash water in processing plants to disinfect harmful food-borne pathogens on fruit and vegetable surfaces. Therefore, to determine the efficacy of our ME biosensors in testing for food-borne pathogens in produce wash water, we assessed the stability of our biosensors in the presence of Clorox and chlorine dioxide. Specifically, Enzyme Linked Immunosorbent Assay (ELISA) was used to study the potential effect of Clorox and chlorine dioxide on the S. Typhimurium capturing ability of our phage probe. At concentrations recommended by the FDA for Clorox (100 ppm free chlorine content) and by the United States Environmental Protection Agency for chlorine dioxide (4 ppm), we observed no negative effect of these chemicals on the stability and S. Typhimurium capturing ability of our phage-displayed oligopeptide probe. These data demonstrate the potential efficacy of using our ME biosensors with phage-displayed oligopeptide probes in produce wash waters to determine the presence of food-borne pathogens.

Rapid Detection of Bacterial Pathogens on 2D Food

This paper investigates a rapid method of detecting bacterial pathogens on 2D food, such as leafy greens. The method is based on our previous work that uses freestanding phage-coated magnetoelastic (ME) biosensors and a surface-scanning coil detector for direct bacterial detection on the surface of food without commonly used sample preparation steps (washing, concentration, enrichment, etc). The ME biosensors used in this work were ferromagnetic alloy strips coated with E2 phage that specifically binds with Salmonella Typhimurium. First, the biosensors (1 mm × 0.2 mm × 30 µm) were placed in rectangular, indexed cavities (1.1 mm × 0.22 mm × 20 µm) that are etched in a glass wafer. A sheet magnet was added to the back of the wafer to hold the sensors in place. The glass wafer with the biosensors and sheet magnet was then flipped and lowered onto Salmonella-tainted spinach leaves. At this time, a weight was added such that the leaves got flattened to improve the chance for the biosensors to physically contact with Salmonella cells. Various weights ranging from 0 g to 120 g were tested to investigate their effects on the Salmonella binding. Measurement sensors loaded with E2 phage and control sensors devoid of the phage were prepared and used. The control sensors served as the reference to compensate for the environmental effects such as temperature and humidity. The biosensors were placed on the surface of the spinach leaves for 2 mins for the binding to occur. The degree of the binding of Salmonella to the measurement sensors was determined by measuring the resonant frequency shift of the sensors using a surface-scanning detection system and confirmed by optical microscopy. The binding of Salmonella was found to increase as the spiked Salmonella concentration increased (103 cfu/ml to 108 cfu/ml). In addition, significant resonant frequency shifts of the measurement sensors (4,800 ± 160 Hz) were observed when 60 g of weight was added. However, further increases in weight did not improve the Salmonella binding with E2 phage. Rather, heavier weights increased the probability of non-specific attachment of Salmonella cells and other residuals from the leaf surface.

Effects of Surface-Scanning Detector Position on the Response of a Wireless Magnetoelastic Biosensor

This paper investigates the effects of surface-scanning detector position on the resonant frequency and signal amplitude of a wireless magnetoelastic (ME) biosensor for direct pathogen detection on solid surfaces. The experiments were conducted on the surface of a polyethylene (PE) plate as a model study. An ME biosensor (1 mm × 0.2 mm × 30 µm) was placed on the PE surface, and a surface-scanning detector was brought close and aligned to the sensor for wireless resonant frequency measurement. The position of the detector was accurately controlled by using a motorized three-axis translation system (i.e., controlled X, Y, and Z positions). The results showed that the resonant frequency variations of the sensor were -125 to +150 Hz for X and Y detector displacements of ± 600 µm and Z displacements of +100 to +500 µm. These resonant frequency variations were small compared to the sensor's initial resonant frequency (< 0.007% of 2.2 MHz initial resonant frequency) measured at the detector home position, indicating high accuracy of the measurement. In addition, the signal amplitude was, as anticipated, found to decrease exponentially with increasing detection distance (i.e., Z distance). Finally, additional experiments were conducted on the surface of cucumbers. Similar results were obtained.

Sensitive Double-Layer Coil Detector for the Detection of Salmonella Typhimurium Using Magnetoelastic Biosensors

The design, simulation, fabrication, and characterization of a highly sensitive double-layer coil detector, utilized with magnetoelastic (ME) biosensors to detect bacterial pathogens, is presented in this paper. The former coil detector was a single-layer coil employed to realize wireless Salmonella detection on various food surfaces, while the double-layer coil in this work has enhancement in sensor excitation and detection sensitivity. With the double-layer coil, not only the wireless detection distance can be further, but also a smaller ME biosensor can be used in the detection to provide higher mass sensitivity. Various coil design parameters, including the thickness of layers, width, height, and spacing of coil turns, were studied. Both theoretical calculations and experimental data showed that the above parameters have a significant impact on the signal amplitude and stand-off distance. Finally, with the newly fabricated double-layer coil detector, detection of Salmonella Typhimurium using multiple biosensors on a food grade Ultra-high-molecular-weight polyethylene (UHMW-PE) board surface was demonstrated. This double-layer coil detector, therefore, facilitates the detection of pathogens on food and food contact surfaces.

Magneto-elastic coupling model of deformable anisotropic superconductors

We develop a magneto-elastic (ME) coupling model for the interaction between the vortex lattice and crystal elasticity. The anisotropies in superconductivity and elasticity are simultaneously included in the GL theory frame. Under this consideration, the expression of the free energy unifies the different forms of the classical results. Concerning the ME effect on the magnetization, the theory can give a satisfying description for the field dependence of magnetization near the upper critical field. The contribution of the ME interaction to the magnetization is comparable to the vortex-lattice energy, in materials with relatively strong pressure dependence of the critical temperature. While the magnetization components along different vortex frame axes are strain dependent, the magnetization ratio is independent of the ME interaction. It is stressed that the GL description of the magnetization ratio is applicable only if the applied field moderately close to the upper critical field.

Influence of antibody immobilization strategies on the analytical performance of a magneto-elastic immunosensor for Staphylococcus aureus detection

Magneto-elastic (ME) sensors have a great advantage in microbiology due to their ability to be queried wirelessly. Staphylococcus aureus is one of the most common bacteria widespread in the environment and a major human pathogen related to numerous illnesses. Immunosensors are affinity-based assays where the analyte is highly selective. The immobilization of antibodies (Ab) is an important step in the development of such devices. This study compared the effects of two antibody immobilization strategies on the analytical performance of a magneto-elastic immunosensor: (1) random antibody covalent immobilization (CysAb) and (2) specific-oriented antibody covalent immobilization (PrGAb). Immunosensors were exposed to solutions containing S. aureus at different concentrations (104 to 108CFU/ml) and sensor resonant frequencies were measured. In order to confirm that the frequency shifts were mainly caused by the binding of S. aureus to the sensor's surface, scanning electron microscope (SEM) and indirect immunofluorescence (IIF) images were taken after bacteria exposure at 108CFU/ml. Sensor surfaces were further monitored by non-contact topographic atomic force microscopy (AFM) images. In the covalent-oriented strategy, PrG was first bound covalently to the surface, which in turn, then binds the anti-S. aureus antibody in an oriented manner. Topographic AFM images showed different surface patterns between the two antibody immobilization strategies. Specific-oriented antibody covalent immobilization (PrGAb) strategy gave the highest anti-S. aureus antibody immobilization density. Therefore, the covalent-oriented strategy presented the best performance for S. aureus capture, detecting 104CFU/ml.

Detection of Salmonella Typhimurium on Spinach Using Phage-Based Magnetoelastic Biosensors.

Phage-based magnetoelastic (ME) biosensors have been studied as an in-situ, real-time, wireless, direct detection method of foodborne pathogens in recent years. This paper investigates an ME biosensor method for the detection of Salmonella Typhimurium on fresh spinach leaves. A procedure to obtain a concentrated suspension of Salmonella from contaminated spinach leaves is described that is based on methods outlined in the U.S. FDA Bacteriological Analytical Manual for the detection of Salmonella on leafy green vegetables. The effects of an alternative pre-enrichment broth (LB broth vs. lactose broth), incubation time on the detection performance and negative control were investigated. In addition, different blocking agents (BSA, Casein, and Superblock) were evaluated to minimize the effect of nonspecific binding. None of the blocking agents was found to be superior to the others, or even better than none. Unblocked ME biosensors were placed directly in a concentrated suspension and allowed to bind with Salmonella cells for 30 min before measuring the resonant frequency using a surface-scanning coil detector. It was found that 7 h incubation at 37 °C in LB broth was necessary to detect an initial spike of 100 cfu/25 g S. Typhimurium on spinach leaves with a confidence level of difference greater than 95% (p < 0.05). Thus, the ME biosensor method, on both partly and fully detection, was demonstrated to be a robust and competitive method for foodborne pathogens on fresh products.

Control of propagation characteristics of spin wave pulses via elastic and thermal effects

A study of the magnetoelastic (ME) and thermal effects governing the phase (φ) and amplitude of magnetostatic surface spin wave (MSSW) pulses propagating in Ga:YIG/GGG and permalloy magnonic waveguides is presented. The ME effects were studied in a flexural configuration, under punctual mechanical force (F). Thermally induced ME and demagnetization phenomena were controlled by optically injected thermal power Pth. It was determined that in an unclamped Ga:YIG waveguide, the force F that induces the phase shift Δφ=π, decreases by a quadratic law in the range from 1 mN to nN, and the Pth at which Δφ=π decreases linearly from mW to μW as the waveguide volume decreases from mm3 to nm3. For nano-volume waveguides the ME control energy (Eme) can be of order of aJ, and the thermal control energy (ΔEth) can be as small as 50fJ. The response time of these effects lies in the ns time scale. Both the mechanical and the thermo-magnetic forces provide an effective control of MSSW pulse amplitude, in addition to its phase shift. The thermo-magnetic effect allows one to realize variable delays of a MSSW pulse.

Effect of Competing Foodborne Pathogens on the Selectivity and Binding Kinetics of a Lytic Phage for Methicillin-Resistant Staphylococcus aureus Detection

The selectivity and binding kinetics of a lytic phage as a new bio-recognition element were compared and evaluated. The selectivity was studied by exposing the magnetoelastic (ME) biosensor to individual cultures of Escherichia coli O157:H7 (EO), Listeria monocytogenes (LM), Salmonella Typhimurium (ST), Vibrio parahaemolyticus, Yersinia enterocolitica, and methicillin-resistant Staphylococcus aureus (MRSA). A dose response of the ME biosensor obtained from serially increasing concentrations of MRSA was then compared with those obtained from MRSA in a mixture of other competing bacteria. The number of MRSA bound on the measurement sensor was 12,206 ± 750 cells/sensor, which was significantly greater than the number of other competing bacteria bound on the sensor (P < 0.001). The dose responses of sensors to increasing concentration of MRSA and MRSA in a mixture of other competing bacteria were similar, indicating that the resonant frequency shifts of the ME sensor were dependent on the concentration of MRSA. The binding valency and dissociation constant (cfu/mL) of the lytic phage with MRSA, MRSA + LM, MRSA + LM + EO, and MRSA + LM + EO + ST were calculated as 3.3 ± 0.2 and 62.5 ± 11.0, 3.7 ± 0.2 and 56.2 ± 11.8, 3.4 ± 0.2 and 59.4 ± 10.5, and 3.7 ± 0.2 and 56.0 ± 10.7, respectively. This study demonstrated that lytic phages were able to bind with MRSA specifically and selectively even in the presence of other competing bacteria.

Magnetoelastic-Sensor Integrated Microfluidic Chip for the Measurement of Blood Plasma Viscosity

This paper presents a microfluidic sensing chip for the quick, low-cost measurement of blood plasma viscosity with a microliter sample volume. This chip is comprised of a magnetoelastic (ME) sensor, a planar measurement coil and a microfluidic system. The ME sensor is a wireless resonating sensor that operates through external magnetic fields. The planar coil is used to both actuate the sensor into mechanical resonance and detect the resonant frequency of the sensor. Due to the planar configuration of the measurement coil, the sensing chip can be fabricated by using a simple integration process (i.e., stacking and bonding) at a low cost. The sample volume required is 100 μL. The sensing chip was first characterized by testing glycerol/water solutions with wide ranges of densities and viscosities. Next, to make a calibration plot correlating the sensor response with liquid viscosity, glycerol/water solutions with finely adjusted viscosities varying from 1.0 cP to 3.0 cP were tested, which covers the viscosity range of human blood plasma. Finally, the sensing chip was used to test various dilutions of human blood plasma samples. The results verify that the proposed sensing chip is capable of quickly measuring viscosity changes in blood plasma of small volume.