Magnetic Micro Research Articles

3D Arrangement of Magnetic Particles in Thin Polymer Films Assisted by Magnetically Patterned Exchange Bias Layer Systems

AbstractThe possibility to arrange and embed magnetic micro‐ and nanoparticles in thin polymer film systems using flat magnetically patterned substrate templates is investigated. In contrast to self‐organized particle rows forming by applying a homogeneous magnetic field, particles adapt to the magnetic field landscape of the substrate's magnetic pattern prior to polymer crosslinking. Crosslinking then fixes the particle positions in the polymer. The process is tested for composites of hydrophobic polydimethylsiloxane (PDMS) and maghemite nanoparticles as well as for hydrophilic polyvinyl alcohol (PVOH) and hydrophilic functionalized, superparamagnetic core–shell microspheres. The substrate template is an exchange bias layer system magnetically patterned into parallel‐stripe domains with in‐plane magnetizations and head‐to‐head/tail‐to‐tail remanent magnetization orientation in adjacent magnetic domains. A high occupancy percentage of magnetic beads on a domain wall as well as anisotropic actuation of the composite is achieved.

Angstrom-Scale Transparent Overcoats: Interfacial Nitrogen-Driven Atomic Intermingling Promotes Lubricity and Surface Protection of Ultrathin Carbon.

Lubricity, a phenomenon which enables the ease of motion of objects, and wear resistance, which minimizes material damage or degradation, are important fundamental characteristics for sustainable technology developments. Ultrathin coatings that promote lubricity and wear resistance are of huge importance for a number of applications, including magnetic storage and micro-/nanoelectromechanical systems. Conventional ultrathin coatings have, however, reached their limit. Graphene-based materials that have shown promise to reduce friction and wear have many intrinsic limitations such as high temperature and substrate-specific growth. To address these concerns, a great deal of research is currently ongoing to optimize graphene-based materials. Here we discover that angstrom-thick carbon (8 Å) significantly reduces interfacial friction and wear. This lubricant shows ultrahigh optical transparency and can be directly deposited on a wide range of surfaces at room temperature. Experiments combined with molecular dynamics simulations reveal that the lubricating efficacy of 8 Å carbon is further improved via interfacial nitrogen.

The Effect of Physiological Incubation on the Properties of Elastic Magnetic Composites for Soft Biomedical Sensors.

Magnetic micro- and nanoparticles (MPs)-based composite materials are widely used in various applications in electronics, biotechnology, and medicine. This group of silicone composites have advantageous magnetic and mechanical properties as well as sufficient flexibility and biocompatibility. These composites can be applied in medicine for biological sensing, drug delivery, tissue engineering, and as remote-controlled microrobots operating in vivo. In this work, the properties of polydimethylsiloxane (PDMS)-based composites with different percentages (30 wt.%, 50 wt.%, 70 wt.%) of NdFeB microparticles as a filler were characterized. The novelty of the work was to determine the influence of the percentage of MP content and physiological conditioning on the properties of the PDMS-MP composites after in vitro incubation. An important essence of the work was a comprehensive study of the properties of materials important from the point of view of medical applications. Materials were tested before and after conditioning in 0.9 wt.% NaCl solution at a temperature of 37 °C. Several studies were carried out, including thermal, physicochemical, and rheological tests. The results show that with an increase of the incubation time, most of the measured thermal and physicochemical parameters decreased. The presence of the magnetic filler, especially at a concentration of 70 wt.%, has a positive effect on thermal stability and physicochemical and rheological properties. The performed tests provided important results, which can lead to further research for a broader application of magnetic composites in the biomedical field.

Thallium extraction in urine and water samples by nanomagnetic 4-Aminothieno[2,3-d] pyrimidine-2-thiol functionalized on graphene oxide

Thallium is a water-soluble metal and extra dosage has toxicological effect in human body. Thallium is readily absorbed by inhalation, ingestion and skin contact. The symptomatology of thallium toxicity was seen in patients with hemorrhage, bone/gastrointestinal problems, delirium, convulsions and coma. So, accurate determination of thallium in water and human urine is necessary. In this research, a novel and applied method based on 25 mg of nanomagnetic 4-Aminothieno[2,3-d] pyrimidine-2-thiol functionalized on graphene oxide (Fe3O4-ATPyHS@GO) was used for thallium extraction in 50 mL of water, wastewater and urine samples by dispersive magnetic micro solid-phase extraction (DM-μ-SPE). After extraction and back-extraction of solid phase by 1 mL of nitric acid solution, the concentration of thallium ions determined by flame atomic absorption spectrometry (F-AAS). The working/linear range, the limit of detection (LOD), and preconcentration factor (PF) were achieved (4-1400 μg L−1; 4-300 μg L−1), 0.9 µg L−1, and 50, respectively (Mean RSD%=1.8 water; 2.1 urine). The absorption capacity of Go and Fe3O4-ATPyHS@GO adsorbent were achieved 7.2 and 137.5 mg g-1 for 5 mg L-1 of thallium, respectively. The procedure was validated by ICP-MS analyzer.

Magnetic dispersive solid phase extraction of ZEAralenone using Fe3O4@ hydroxy propyl methyl cellulose nanocomposite from wheat flour samples prior to fluorescence determination: Multivariate optimization by Taguchi design

The contamination of cereals and cereal products with ZEAralenon (ZEA) is a permanent challenge in human health. A new, sensitive, and fast magnetic dispersive micro solid phase extraction (Magnetic D-µ-SPE) was developed for preconcentration and quantitative spectrofluorometric determination of ZEA in wheat flour samples. The Fe3O4@hydroxypropyl methylcellulose (Fe3O4@HPMC) nanocomposite was prepared and used as an efficient magnetic adsorbent. The characterization of the synthesized nanocomposite by the co-precipitation method was confirmed by the FT-IR, TEM, XRD, and VSM analysis. Taguchi L16 array was used for the design of experiments to investigate the influences of extraction parameters on the recovery percentage of µ-SPE. A pH of 4, a magnetic nanoparticle weight of 30 mg, ionic strength of (6 w/v %), extraction time of 3 min, desorption time of 6 min, and 500 µL of MeOH as an efficient eluent solvent were the optimized extraction parameters. Under the optimal working conditions, this method showed good linearity in the range of 8–320 ng g−1 (R2 = 0.9991) with a limit of detection of 6.01 ng g−1. The method recoveries ranged from 83.8 to 111.0 % for wheat flour samples. The results showed that this simple, inexpensive method with low organic solvent consumption was accurate and significantly free from interference effects. The proposed method was successfully applied to determine trace amounts of ZEA from wheat flour sample matrices. This method is rapid with an average extraction time of 9 min and high enrichment (~53 %) and has many advantages such as operational simplicity without using expensive methods such as HPLC or immunoassay column, minimization of solvent utilization, and good accuracy.

Recent progress in magnetic applications for micro- and nanorobots

In recent years, magnetic micro- and nanorobots have been developed and extensively used in many fields. Actuated by magnetic fields, micro- and nanorobots can achieve controllable motion, targeted transportation of cargo, and energy transmission. The proper use of magnetic fields is essential for the further research and development of micro- and nanorobotics. In this article, recent progress in magnetic applications in the field of micro- and nanorobots is reviewed. First, the achievements of manufacturing micro- and nanorobots by incorporating different magnetic nanoparticles, such as diamagnetic, paramagnetic, and ferromagnetic materials, are discussed in detail, highlighting the importance of a rational use of magnetic materials. Then the innovative breakthroughs of using different magnetoelectric devices and magnetic drive structures to improve the micro- and nanorobots are reviewed. Finally, based on the biofriendliness and the precise and stable performance of magnetic micro- and nanorobots in microbial environments, some future challenges are outlined, and the prospects of magnetic applications for micro- and nanorobots are presented.

Aptamer-based assays: strategies in the use of aptamers conjugated to magnetic micro- and nanobeads as recognition elements in food control

An outlook on the current status of different strategies for magnetic micro- and nanosized bead functionalization with aptamers as prominent bioreceptors is given with a focus on electrochemical and optical apta-assays, as well as on aptamer-modified magnetic bead–based miniaturized extraction techniques in food control. Critical aspects that affect interaction of aptamers with target molecules, as well as the possible side effects caused by aptamer interaction with other molecules due to non-specific binding, are discussed. Challenges concerning the real potential and limitations of aptamers as bioreceptors when facing analytical problems in food control are addressed.Graphical abstract

An in situ modification sorbent for magnetic dispersive micro solid-phase extraction of anti-inflammatory drugs in the human urine sample before their determination with high-performance liquid chromatography

An in situ modification sorbent for magnetic dispersive micro solid-phase extraction of anti-inflammatory drugs in the human urine sample before their determination with high-performance liquid chromatography

Simultaneous determination of organophosphorus pesticides residues in vegetable, fruit juice, and milk samples with magnetic dispersive micro solid-phase extraction and chromatographic method; recruitment of simplex lattice mixture design for optimization of novel sorbent composites

Dispersive micro solid-phase extraction procedure using a novel and selective sorbent prepared from four components was developed as a sample preparation strategy for extracting five organophosphorus pesticides, including fenitrothion, malathion, ethion, and chlorpyrifos, and diazinon in several vegetables, fruit juices, and cow's milk samples. Due to the high importance of the sorbent in the microextraction process, the percentages of sorbent components, including metal-organic framework (ZIF-67), chitosan, magnetic Fe3O4 nanoparticles, and silica nanoparticles, were optimized by a simplex lattice mixture design. After optimizing the sorbent composite, effective parameters on the extraction of organophosphorus pesticides were optimized using a definitive screening design and Box-Behnken design, respectively. A surfactant (Triton X100) as a dispersion agent with a low volume (10 μL) was utilized in the microextraction procedure to reduce the sorbent dispersion time and increase the sorbent dispersion efficiency. Under the optimal conditions, linearity for the determination of fenitrothion, malathion, ethion, chlorpyrifos, and diazinon was in the concentration ranges of 0.13–1100, 0.27–1000, 0.38–1000, 0.21–1200, and 0.11–1100 ng mL−1 with a determination coefficient higher than 0.9906, respectively. The quantitation limits, detection limits, and relative standard deviations (n = 5) were lower than 0.38 ng mL−1, 0.11 ng mL−1, and 4.59% for the determination of organophosphorus pesticides. The method application for measuring OPPs on cucumber, carrot, tomato, apple juice, orange juice, and cow's milk indicated the presence of residual amounts of malathion in a cucumber sample, diazinon in a carrot sample, and chlorpyrifos in a tomato sample.

Magnetic Nanodiscs-A New Promising Tool for Microsurgery of Malignant Neoplasms.

Magnetomechanical therapy is one of the most perspective directions in tumor microsurgery. According to the analysis of recent publications, it can be concluded that a nanoscalpel could become an instrument sufficient for cancer microsurgery. It should possess the following properties: (1) nano- or microsized; (2) affinity and specificity to the targets on tumor cells; (3) remote control. This nano- or microscalpel should include at least two components: (1) a physical nanostructure (particle, disc, plates) with the ability to transform the magnetic moment to mechanical torque; (2) a ligand—a molecule (antibody, aptamer, etc.) allowing the scalpel precisely target tumor cells. Literature analysis revealed that the most suitable nanoscalpel structures are anisotropic, magnetic micro- or nanodiscs with high-saturation magnetization and the absence of remanence, facilitating scalpel remote control via the magnetic field. Additionally, anisotropy enhances the transmigration of the discs to the tumor. To date, four types of magnetic microdiscs have been used for tumor destruction: synthetic antiferromagnetic P-SAF (perpendicular) and SAF (in-plane), vortex Py, and three-layer non-magnetic–ferromagnet–non-magnetic systems with flat quasi-dipole magnetic structures. In the current review, we discuss the biological effects of magnetic discs, the mechanisms of action, and the toxicity in alternating or rotating magnetic fields in vitro and in vivo. Based on the experimental data presented in the literature, we conclude that the targeted and remotely controlled magnetic field nanoscalpel is an effective and safe instrument for cancer therapy or theranostics.

A reciprocating permanent magnetic actuator for driving magnetic micro robots in fluids

Magnetic-based driving applications are receiving increasing attention. This study proposed a novel reciprocating permanent magnetic actuator (PMA) to manipulate magnetic micro robots to impact and clear blockages inside fluid pipes in a linear path. The PMA consisted of a cylindrical permanent magnet and a crank slider structure. A straight pipe with a circular cross-sectional area was located in front of the actuator to study the driving performance of PMA. A micro permanent magnet with a cylinder shape was employed as a working robot for manipulation inside the pipe. Firstly, analytical formulas were derived to obtain the magnetic driving force acting on the micro robot and determine the most suitable magnet configuration. The finite element simulation verified the analytical calculation. The developed reciprocating PMA prototype was then introduced, and the PMA and micro robot’s motion performance was analysed. Lastly, preliminary experiments were carried out for evaluating the micro robot’s motion characteristics. Performance tests for different excitation frequencies, flow rates, viscosities, and axial distances, indicating that PMA could manipulate the magnetic micro robot inside the pipe. The results confirmed that the developed PMA could effectively drive the micro robot with the advantage of consecutive magnetic driving. Especially, the micro robot featured good flexibility, rapid response, and a simple structure, suggesting that this micro robot may play an important role in industrial and medical applications, such as blockage elimination and thrombus clearance.

Self-Assembly Magnetic Micro- and Nanospheres and the Effect of Applied Magnetic Fields.

The impact of in-plane and perpendicular magnetic fields on the spatial arrangement of superparamagnetic nanospheres is explored. We utilize nanosphere self-organization methods like Spin Coating and Drop-Casting in the presence of magnetic fields. In this way, the additional parameter of the long range magnetic dipolar interactions is introduced to the competing nanosphere–surface and nanosphere–nanosphere interactions, which control order and agglomeration. We present a comparative analysis of the self-assembly characteristics with respect to the different methods and the effect of the applied field in different directions. Under zero field perfect hexagonal arrays can be obtained by spin coating. Parallel applied fields tend to create directional patterns, while perpendicular favor 3D-accumulation.

Magnetic Microswarm Composed of Porous Nanocatalysts for Targeted Elimination of Biofilm Occlusion.

Biofilm is difficult to thoroughly cure with conventional antibiotics due to the high mechanical stability and antimicrobial barrier resulting from extracellular polymeric substances. Encouraged by the great potential of magnetic micro-/nanorobots in various fields and their enhanced action in swarm form, we designed a magnetic microswarm consisting of porous Fe3O4 mesoparticles (p-Fe3O4 MPs) and explored its application in biofilm disruption. Here, the p-Fe3O4 MPs microswarm (p-Fe3O4 swarm) was generated and actuated by a simple rotating magnetic field, which exhibited the capability of remote actuation, high cargo capacity, and strong localized convections. Notably, the p-Fe3O4 swarm could eliminate biofilms with high efficiency due to synergistic effects of chemical and physical processes: (i) generating bactericidal free radicals (•OH) for killing bacteria cells and degrading the biofilm by p-Fe3O4 MPs; (ii) physically disrupting the biofilm and promoting •OH penetration deep into biofilms by the swarm motion. As a demonstration of targeted treatment, the p-Fe3O4 swarm could be actuated to clear the biofilm along the geometrical route on a 2D surface and sweep away biofilm clogs in a 3D U-shaped tube. This designed microswarm platform holds great potential in treating biofilm occlusions particularly inside the tiny and tortuous cavities of medical and industrial settings.

Nanographene oxide modified phenyl methanethiol nanomagnetic composite for rapid separation of aluminum in wastewaters, foods, and vegetable samples by microwave dispersive magnetic micro solid-phase extraction

A new method based on graphene oxide modified (4-phenyl) methanethiol nanomagnetic composite (Fe3O4@4-PhMT-GO) was used for extraction and separation of aluminum from wastewater, food, and vegetable samples in aluminum cookware by microwave dispersive magnetic micro solid-phase extraction (MDM-μ-SPE). In optimized conditions, the working range (WR), the linear range (LR), the limit of detection (LOD), and enrichment factor (EF) were obtained 5–5200 μg L−1, 5–1600 μg L−1, 1.5 µg L−1, and 48.8, respectively (RSD% = 2.5). By MDM-μ-SPE procedure, the aluminum concentrations in baking rice and spinach with aluminum cookware were obtained 97.43 ± 2.57 mg g−1 and 131.64 ± 5.18 mg g−1, respectively which was analyzed by atom trap flame atomic absorption spectrometer (AT-FAAS). The results showed, the aluminum concentrations in cooked foods with Teflon cookware were less than aluminum cookware. The methodology was validated by standard reference materials (SRM) and inductively coupled plasma mass spectrometry analysis (ICP-MS).

Comparison of two polythiophene nanocomposites-based dispersive micro solid-phase extraction procedures coupled with salt-induced/magnetic separations for efficient preconcentration of toxic metal ions from food samples

For the first time, the polythiophene nanocomposite-based air-agitated dispersive micro solid-phase extraction coupled with salt-induced decantation is proposed for the preconcentration of the Pb(II) and Co(II) ions in the food samples. The nanoadsorbent was first synthesized via an in situ sonochemical oxidative polymerization method in the presence of FeCl3, as the oxidant, and other additives, including sodium dodecylbenzene sulfonate and ZnO nanoparticles (NPs). The use of an inorganic salt in the centrifugation step was influential on the separation of this highly soft nanocomposite. In the next step, the developed approach was statistically compared with the air-agitated magnetic micro solid-phase extraction method based on the same sorbent substrate but conjugated with magnetic NPs to retrieve the highly soft nanocomposite via magnetic forces. Under the optimal conditions, the two procedures provided comparable linear dynamic ranges with the correlation of determinations higher than 0.98. The detection limits obtained were satisfactory (8.0–10 ng mL−1 for the salt-induced dispersive solid-phase extraction and 0.7–1.5 ng mL−1 for magnetic assisted dispersive solid-phase extraction). The calculated enrichment factor values were approximately the same for the two procedures. In addition, the magnetic dispersive solid-phase extraction procedure enjoyed appropriate repeatability. These satisfactory validations satisfy the high efficiency of the salt-induced and magnetic procedures and the effectiveness of the used nanocomposites to establish versatile retention mechanisms without any crucial demand for the derivatization or complexing agents.

Mechanisms dominating thixotropy in limestone calcined clay cement (LC3)

Limestone calcined clay cement (LC3) is a green binder with great practical importance for the cement industry. Growing application has increased the need to understand the mechanisms governing its thixotropy for better control of workability. While formation of C-S-H bridges is understood to dominate the thixotropy of ordinary Portland cement, LC3 paste displayed unique thixotropy properties. In this study, focused beam reflectance measurement, zeta potential, 1H nuclear magnetic resonance relaxometry and micro X-ray computed tomography were used to track the colloidal interaction and hydration extent within LC3 paste. Results showed that flocculation due to the negative surface charge and water affinity of calcined clay appears to be the dominating factor. This leads to a reduction of water available to contribute to fluidity of the paste and, in turn, governing the development of thixotropy over time. In addition, the dilution effect due to high clinker substitution diminishes thixotropy growth with time.

A novel technology of recovering magnetic micro particles from spent lithium-ion batteries by ultrasonic dispersion and waterflow-magnetic separation

With the rapid growth of lithium ion batteries (LIBs) market, large Numbers of LIBs are nearing the end of their life cycle. At the same time, large number of magnetic energy metals (MEMs) demand is difficult to meet. It is an urgent demand to recover micro magnetic particles from spent LIBs. However, the aggregates formed by micro particles make it difficult to be separated by mechanical technologies. Existing mechanical separating technologies are limited by strict particle size of larger than 0.075 mm. Chemical technologies can recover micro metallic particles without considering particle size but take the risks of environmental pollution. We developed a technology of ultrasonic dispersion and waterflow-magnetic separation to recover micro magnetic particles from mixed micro particles aggregates. By analyzing the relationship between aggregation energy and size of aggregates, the key factors to destroy the aggregation of micro particles were determined. The optimal parameters of ultrasonic dispersion were obtained by experiments. Under the condition of 20 min ultrasonic time, 200 W ultrasonic power, the maximum recovery rate of cobalt particles was 99.63% ± 0.62% and the purity of cobalt particles was 93.15% ± 0.56%. Combining with the trajectory of particles in waterflow-magnetic separation, key parameters influencing recovery effect were determined. This study provided a new technology for the separation of micro MEMs particles and aggregates.

Development and Performance Evaluation of Solid-Free Drilling Fluid for CBM Reservoir Drilling in Central Hunan

Solid-free drilling fluid is a matter of cardinal significance in the course of Coal bed Methane (CBM) reservoir drilling. This study evaluated the performance of solid-free CBM drilling fluid in central Hunan. Three types of surfactants, namely TX-10 (nonionic), HSB1618 (zwitterionic) and penetrant T (anionic), were added in basic fluid at various concentrations of 0.05, 0.10 and 0.15% (m/m). This study comprised of drilling fluid rheology, sample mineral analysis, sample nuclear magnetic resonance (NMR) scanning, sample wettability, and sample surface micro characteristics tests. The results show that TX-10 and HSB1618 enhance the rheological properties of drilling fluid, such as yield point and gel strength. Penetrant T has opposite effect on it. It was found that the minimum American Petroleum Institute (API) filtration is only 0.3 mL. This study adopted a new method using laser particle size analyzer to evaluate suspension performance. Based on the surface micro characteristics of the sample and the NMR scanning tests, it is found that the residual amount of basic fluid + HSB1618 in the sample is the smallest. The wettability modification curve indicates that three surfactants decrease the sample’s hydrophobicity. With the increase of surfactant concentration, all above parameters change regularly. The basic fluid + 0.10% HSB1618 has the strongest hydrophobicity for sample at pH = 10. This study obtained a set of solid-free drilling fluid system, which provides better suspension capacity and large contact angle and reduces residue of drilling fluid in CBM reservoir. Ultimately, it can accelerate the desorption of coal gas and reduce damage to the reservoir.

Comparison of Biodiesel Production Using the Oil of Chlorella Vulgaris Micro-algae by Electrolysis and Reflux Methods Using CaO/KOH-Fe3O4 and KF/KOH-Fe3O4 as Magnetic Nano catalysts

Today, most of the biodiesel is made by using vegetative or animal oils as raw materials, so, the cost of biodiesel production is arising from raw materials. By considering problems raised from raw materials price and process time, cost of the catalysts and reducing food resources, in this study, it is attempted to reduce these costs by using magnetic nano catalysts (CaO/KOH-Fe3O4 and Fe3O4-KF/KOH) and nonedible oils (micro-algae strain, namely Chlorella Vulgaris) to compare two methods of producing biodiesel (Transesterification with reflux and electrolysis, magnetic nano catalysts were prepared using sedimentation and centrifugation methods and characterized by X-Ray Diffraction patterns. Different condition for reflux method were investigated, Due to the magnetic properties of these catalysts, they have a high interaction in the reaction medium and also have a high surface area which results in increased reaction efficiency and reducing the reaction time in order to achieve the highest efficiency, Furthermore, Magnetic nano catalysts are recoverable and can be recovered by using an external magnetic field and, at the same time, it maintains a high catalytically activity and this property reduces the reaction costs and ultimately the cost of biodiesel production. The results showed the optimum values were 1.5 wt% of the catalyst weight, molar ratio of alcohol to oil (6:1), and the reaction time of 360 min to achieve the maximum yield of 80% using KF/KOH-Fe3O4 nano catalyst along with saponification side reaction. In addition, using electrolysis method resulted in the maximum process yield of 98.1% with the same nano catalyst and non-saponification side reaction. Therefore, using electrolysis method with KF/KOH-Fe3O4 magnetic nano catalyst and micro algae as the feed, showed the higher mass yield in transesterification reaction. Furthermore, the prepared biodiesel was in accordance with the world standard of fuel.

Immunomagnetic Separation of Salmonella with Tailored Magnetic Micro- and Nanocarriers.

One of the main drawbacks in current methods for bacterium detection is their quantification at very low concentration level in complex specimens. Novel developments that are needed involve solid-phase preconcentration procedures which can be easily integrated with emerging technologies. Here, we describe the immunomagnetic separation (IMS) of Salmonella using magnetic carriers. Nano (300nm) and micro (2.8μm) sized magnetic particles are modified with anti-Salmonella antibody to preconcentrate the bacteria from the samples throughout an immunological reaction. The immunomagnetic separation can be easily coupled with downstream characterization and quantification methods, including classical culturing, molecular biology techniques such as PCR, immunoassays, confocal and scanning electron microscopy, and emerging technologies and rapid detection methods including biosensors, lateral flow, and microfluidic devices.