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Conventional micro-particle manipulation technologies have been used for various biomedical applications using dynamics on a plane without vertical movement. In this case, irregular topographic structures on surfaces could be a factor that causes the failure of the intended control. Here, we demonstrated a novel colloidal particle manipulation mediated by the topographic effect generated by the "micro hill" and "surface gradient" around a micro-magnet. The magnetic landscape, matter orbital, created by periodically arranged circular micro-magnets, induces a symmetric orbit of magnetic particle flow under a rotating magnetic field. The topographic effect can break this symmetry of the energy distribution by controlling the distance between the source of the driving force and target particles by several nanometers on the surface morphology. The origin symmetric orbit of colloidal flow can be distorted by modifying the symmetry in the energy landscape at the switching point without changing the driving force. The enhancement of the magnetic effect of the micro-magnet array can lead to the recovery of the symmetry of the orbit. Also, this effect on the surfaces of on-chip-based devices configured by symmetry control was demonstrated for selective manipulation, trapping, recovery, and altering the direction using a time-dependent magnetic field. Hence, the developed technique could be used in various precise lab-on-a-chip applications, including where the topographic effect is required as an additional variable without affecting the existing control method.

Recently, miniaturized electrochemical biosensors have the advantage of real-time monitoring and label-free detection of biomarkers. However, controlled manipulation of reagent samples for specific immobilization of biomarkers remains a challenge to attend high-resolution microfluidic biosensor. Here, we designed a microfluidic channel and valves integrated electrochemical biosensor for the detection of β-amyloid (1–42) biomarker, one of the most neurotoxic peptides present in the cerebrospinal fluid, and a possible marker for the detection of Alzheimer's disease. The formation of the antibody-antigen complexes on gold microelectrode integrated inside the fluidic chambers was presented in the developed biosensor, and all the measurements are carefully controlled using pneumatic valves integrated with the device. The demonstrated microfluidic electrochemical biosensor exhibits a linear response towards various β-amyloid antigen concentrations from 2.2 pM to 22 μM, with an enhanced detection limit of 1.62 pM. The developed technology offers an advantage of minimal reagent sample and suitable environment for miniaturized and sensitive detection of biomarkers, could also be used for the detection of other biomarkers with high efficiency.

Mission-critical embedded systems simultaneously run multiple graphics-processing-unit (GPU) computing tasks with different criticality and timeliness requirements. Considerable research effort has been dedicated to supporting the preemptive priority scheduling of GPU kernels. However, hardware-supported preemption leads to lengthy scheduling delays and complicated designs, and most software approaches depend on the voluntary yielding of GPU resources from restructured kernels. We propose a preemptive GPU kernel scheduling scheme that harnesses the idempotence property of kernels. The proposed scheme distinguishes idempotent kernels through static source code analysis. If a kernel is not idempotent, then GPU kernels are transactionized at the operating system (OS) level. Both idempotent and transactionized kernels can be aborted at any point during their execution and rolled back to their initial state for reexecution. Therefore, low-priority kernel instances can be preempted for high-priority kernel instances and reexecuted after the GPU becomes available again. Our evaluation using the Rodinia benchmark suite showed that the proposed approach limits the preemption delay to 18 $\mu$ μ s in the 99.9th percentile, with an average delay in execution time of less than 10 percent for high-priority tasks under a heavy load in most cases.

Herein, we have developed a novel high-resolution electrochemical biosensor for the detection of the microRNA-122 (miRNA-122) using gold nanoparticles dotted reduced graphene oxide (rGO/Au) nanocomposite. The natural soapnut solution was used as a reducing agent for the synthesis of the nanocomposite. The naturally reduced rGO/Au nanocomposite was confirmed through various characterization techniques. When rGO/Au nanocomposite was coated on to the gold electrode and checked the electrochemical performance, the nanocomposite shows superior analytical performance. The probe DNA was anchored onto the binding sites of rGO/Au nanocomposite through thiol linker and recognized the target miRNA-122. The developed rGO/Au based electrochemical biosensor demonstrated a linear response for various target miRNA-122 concentrations with a range from 10 μM to 10 pM and, with a detection limit of 1.73 pM. The developed biosensor also shows good stability and reproducibility, could be used for the detection of miRNA-122 and, also can be used for the basic research and clinical studies. Besides, the demonstrated rGO/Au nanocomposite-based sensing strategy could be used to detect various miRNA and protein biomarkers. Furthermore, the green synthesis approach could also be useful for the synthesis of various nanomaterials and nanocomposites for various biomedical applications.

Controllable synthesis of graphene-coated metal nanoparticles (NPs) presents a major challenge when considering the practical application of these catalysts. Herein, we use silica as a radical sieve to grow graphene over cobalt NPs via chemical vapor deposition. As-prepared single-layer graphene-coated cobalt NPs with and without N doping (Co@N-SG and Co@SG) exhibit noticeable oxygen evolution reaction (OER) activity. Furthermore, a magnet-assisted binder-free Co@N-SG electrode illustrates much improved OER activity and stability over conventional binder-assisted counterparts, suggesting this as an effective way to overcome the recognized issues of high electron transfer resistance and poor adhesion of binder-based electrodes in practical applications. Interestingly, the graphene shell possesses varying defects and major OER benefitting active sites are found around said defects in the shell, while separately isolated Co@SG with a defect-free shell, despite exhibiting a slightly lower initial activity, illustrates a much-improved durable OER performance. The underlying Co affects the electron density of the graphene shell through dipole interaction and the electron density is optimized for adsorption of reaction intermediates, hence accelerating OER performance. This work will provide new clues to design efficient and durable electrocatalysts with further enhanced OER performance.

We demonstrated a simple one-pot synthesis approach for the controlled composition of homogeneous FePt and phase-controlled heterostructured FePt/Fe3O4 nanocubes (NCs) utilizing 1,2-hexadecanediol and 1-octadecene as the reducing agents, respectively. When the Fe : Pt precursor ratio was varied from 1 : 1 to 4 : 1 and 1,2-hexadecanediol was utilized as the reducing agent, homogeneous FePt NCs were formed, whereas the heterostructures of FePt/Fe3O4 NCs were obtained when utilizing 1-octadecene as the reducing agent at Fe : Pt ratio of 4 : 1. The initial domination of nucleation of Pt-rich species and the subsequent deposition of Fe atoms leads to the formation of homogeneous FePt NCs. Heterostructured FePt/Fe3O4 NCs were obtained by the initial FePt seed formation, which was then followed by the heterogeneous growth of Fe3O4. The heterostructured FePt/Fe3O4 NCs exhibited two phases, i.e., FePt phase with a (111) facet of the fcc and Fe3O4 phase with an inverse cubic spinel structure. Moreover, both the FePt and the FePt/Fe3O4 NCs demonstrated almost negligible coercivity, which confirmed a typical superparamagnetic behavior. Furthermore, the cell viability tests of the FePt and FePt/Fe3O4 NCs demonstrated excellent biocompatibilities. Hence, the NCs could be useful for various biomedical applications, including MRI contrast agents, hyperthermia, and as a label in magnetic biochips.

Herein, we have reported the real-time photodegradation of methylene blue (MB), an organic pollutant, in the presence of sunlight at an ambient temperature using a platinum-decorated reduced graphene oxide (rGO/Pt) nanocomposite. The photocatalyst was prepared via a simple, one-pot and green approach with the simultaneous reduction of GO and Pt using aqueous honey as a reducing agent. Moreover, the honey not only simultaneously reduced Pt ions and GO but also played a key role in the growth and dispersion of Pt nanoparticles on the surface of rGO. Various rGO/Pt nanocomposites with different percentages of Pt nanoparticles loaded on rGO were obtained by tuning the concentration of the Pt source. The high percentage of Pt nanoparticles with an average size of 2.5 nm dispersed on rGO has shown excellent electrochemical performance. The photocatalytic activity of the rGO/Pt composite was enhanced by increasing the weight percent of the Pt particles on rGO, which led to the formation of a highly efficient photocatalyst. The optimized photocatalyst exhibited remarkable photocatalytic activity and degraded 98% MB in 180 minutes; thus, it can be used for industrial and environmental applications.

A set of planar Hall resistance (PHR) sensors was fabricated on rigid and flexible substrates. High signal-to-noise ratio, low offset voltage, nearly zero hysteresis of signal, and excellent linearity were demonstrated for sensors, based on Ta (5 nm)/NiFe (10 nm)/IrMn (10 nm)/Ta (5 nm) thin films, grown on polydimethylsiloxane (PDMS) and parylene C polymeric substrates. The effect of bending on the performance of the PHR sensors was studied. The effect of bending deformation on the performance characteristics of the fabricated PHR sensors is reversible until the bending angle reaches a critical one. The critical bending angle is shown to depend on the substrate composition. An irreversible deformation of a sensor's film, accompanied by the formation of wrinkles and cracks, occurs when the bending angle exceeds the critical one. This deformation originates from the difference between the values of Young's modulus of the substrate and the film. The bending stability of a PHR sensor, grown on PDMS substrate, was improved by deposition of 1 µm of parylene C as a buffer and as a capping layer. The performance characteristics of the designed bendable PHR sensors are compatible with requirements for applications in wearable electronics and medical diagnostic devices.

High thermal stability of the planar Hall resistance (PHR) signal in magnetic sensors, configured as a cross-junction and as a Wheatstone bridge, has been demonstrated. The thermal drift of the PHR signal, which is proportional to the PHR offset at zero field, is few orders of magnitude less than the thermal drift of the anisotropic magnetoresistance signal. The thermal drift of the PHR originates from two independent components: baseline drift and signal amplitude drift. The temperature coefficient of baseline drift, normalized by zero-field offset, is similar to the temperature coefficient of resistance. This makes it possible to characterize drift in any temperature range by a single measurement of PHR under ambient conditions. Signal amplitude drift is shown to be dependent on a sensor's geometry, and becomes higher with a reduction of the width of the current path. The temperature coefficients of baseline drift and signal amplitude drift are of opposite sign. The possibility of mutual compensation of signal amplitude drift and baseline drift by a slight imbalance in a bridge-type sensor is demonstrated.

Advances in micro- and nanotechnology have led to rapid employment of spintronic sensors in both recording and non-recording applications. These state-of-the-art magnetoresistive spintronic sensors exhibit high sensitivities and ultra-low field detectivities that meet requirements of smart sensing applications in the fields of internet of things, mobile devices, space technology, aeronautics, magnetic flux leakage, domotics, the environment, and healthcare. Moreover, their ability to be customized and miniaturized, ease of integration, and cost-effective nature make these sensors uniquely competitive with regard to mass production. In this study, we discuss magnetoresistive field sensors based on the planar-Hall effect, which are very promising for their high sensitivity and sensing ultra-low magnetic fields. We provide a detailed historical overview and discuss recent dramatic developments in several application fields. In addition, we discuss sensor material property requirements, design architectures, noise-reduction techniques, and sensing capabilities, along with the high repeatabilities and good flexibility characteristics of such devices. All of these high-performance characteristics apply across a wide temperature range and make the sensor robust when used in various novel applications. The sensor also appears promising because it is cost-effective and can be used in micro-sensing applications. Recently, a noteworthy study that combined integrated planar-Hall magnetoresistive sensors with microfluidic channels revealed their potential for highly localized magnetic field sensing. This characteristic makes them suitable for point-of-care-technologies that require resolutions of a few pT at room temperature.

We demonstrated a simple one-pot synthesis approach for the controlled composition of homogeneous FePt and phase-controlled heterostructured FePt/Fe

Manipulating and separating single label-free cells without biomarker conjugation have attracted significant interest in the field of single-cell research, but digital circuitry control and multiplexed individual storage of single label-free cells remain a challenge. Herein, by analogy with the electrical circuitry elements and electronical holes, we develop a pseudo-diamagnetophoresis (PsD) mattertronic approach in the presence of biocompatible ferrofluids for programmable manipulation and local storage of single PsD holes and label-free cells. The PsD holes conduct along linear negative micro-magnetic patterns. Further, eclipse diode patterns similar to the electrical diode can implement directional and selective switching of different PsD holes and label-free cells based on the diode geometry. Different eclipse heights and junction gaps influence the switching efficiency of PsD holes for mattertronic circuitry manipulation and separation. Moreover, single PsD holes are stored at each potential well as in an electrical storage capacitor, preventing multiple occupancies of PsD holes in the array of individual compartments due to magnetic Coulomb-like interaction. This approach may enable the development of large programmable arrays of label-free matters with high throughput, efficiency, and reliability as multiplex cell research platforms., Here, the authors present a pseudo-diamagnetophoresis mattertronic approach for programmable manipulation of label-free cells. Immersed in biocompatible ferrofluids, single cells are moved along linear negative micromagnetic patterns, switched at eclipse diode patterns and stored in potential wells.

Herein, we have reported the real-time photodegradation of methylene blue (MB), an organic pollutant, in the presence of sunlight at an ambient temperature using a platinum-decorated reduced graphene oxide (rGO/Pt) nanocomposite. The photocatalyst was prepared

Barkhausen noise, driven by thermal fluctuations in stationary magnetic field, and Barkhausen jumps, driven by sweeping magnetic field, are demonstrated to be effects of different orders of magnitude. The critical magnetic field for domain walls depinning, followed by avalanched and irreversible magnetization jumps, is determined. Magnetoresistive response of NiFe/M/NiFe (M = Au, Ta, Ag) trilayers to stationary and sweeping magnetic field is studied by means of anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) measurements. Thermal fluctuations result in local and reversible changes of magnetization of the layers in thin film magnetic junctions, while the sweeping magnetic field results in reversible and irreversible avalanched domain motion, dependently on the ratio between the values of sweeping magnetic field and domain wall depinning field. The correlation between AMR and PHE responses to Barkhausen jumps is studied. The value of this correlation is found to be dependent on the α angle between the directions of magnetic field and current path.

The development of environmentally benign, low-processing and low-cost approaches to the large-scale preparation of advanced nanomaterials based on the use of biological materials is currently attracting great interest. Here, we report the discovery that aqueous honey solutions reduce graphene oxide in a low-cost and an eco-friendly manner, yielding highly water dispersive functionalized reduced graphene sheets. The roles of honey in the reduction of graphene oxide of as-prepared graphene are demonstrated. The possible mechanism for the de-epoxidation of graphene oxide is elucidated. The fabricated a honey-reduced graphene oxide-based field-effect transistor exhibited ambipolar transfer characteristics, thereby demonstrating that the developed material may therefore have applications in electronic devices and sensors.

We fabricate on-chip micromagnets using Ni80Fe20 and Co70Fe30 materials for the characterization of mobility of superparamagnetic particles. The maximum velocity of the particles around the periphery of the micromagnets is determined by the critical frequency, which indicates that the particle enters the phase-slipping regime from the phase-locked regime. The maximum velocity of NiFe micromagnets is approximately 3 times larger than that of CoFe micromagnets measured at the low field regions. Moreover, the maximum velocity of the particles is decreasing with increasing the thickness of Teflon coating on the micromagnets, which is in a good agreement with the variation of the magnetostatic potential energy evaluated numerically from micromagnetic simulations.

Magnetic flux leakage (MFL) detection is frequently used for oil and gas pipeline inspection, especially for evaluation of the integrity of pipelines. The success of the MFL technique depends on many parameters. However, a sensitive magnetic sensor is an important requirement. Therefore, magnetic field sensors based on different mechanisms have been developed and applied to the MFL technique. In this paper, we evidence for the first time the capability of an innovative device based on a planar Hall magnetoresistance sensor devoted to MFL detection. This promising prototype combines all the required qualifications such as high sensitivity, low thermal drift, and bipolar and linear responses to the magnetic field. New achievements are carried out on embedded sensors in a testing platform reflecting pipeline environments. The ultrasensitive magnetic mapping concludes to a convincing technical approach with a high potential application toward MFL inspection, especially for the detection of shallow defects appearing at near side, far side, and sub-surface of a pipe wall.

A sensitive and selective microfluidic immunochip was fabricated for detection of Salmonella typhimurium ( S. typhimurium ) bacterial cells. In this sensor, graphene oxide (GO) nano sheets wrapped carboxylated multiwalled carbon nanotubes (cMWCNTs) composite acted as a transducer material. The colloidal solution of GO-cMWCNTs composite was selectively deposited onto patterned indium tin oxide (ITO) electrode and sealed with polydimethylsiloxane (PDMS) micro channels. The S. typhimurium antibodies (StAb) were in situ biofunctionalized followed by EDC-NHS covalent chemistry via amidation reaction. The presence of abundant functional groups at the GO-cMWCNTs composite improved the loading of antibodies (StAb) against S . typhimurium leading to improved biosensing characteristics. Wrapping of cMWCNTs with GO resulted in superior electron transfer behavior enhancing the sensitivity (162.47 μA/CFU −1 /mLcm −2 ) almost two folds as compared to that based on GO (89.16 μA/CFU −1 /mLcm −2 ) sheets for bacterial cells detection. Besides this, GO wrapped cMWCNTs integrated microfluidics biosensor offered low detection limit as 0.376 CFU/mL and negligible interference due to presence of Escherichia coli ( E. coli (O157:H7).

Cell clustering techniques are important to produce artificial cell clusters for in vitro models of intercellular mechanisms at the single-cell level. The analyses considering physical variables such as the shape and size of cells have been very limited. In addition, the precise manipulation of cells and control of the physical variables are still challenging. In this paper, a magnetophoretic device consisting of a trampoline micromagnet and active elements that enable the control of individual selective jumping motion and positioning of a micro-object is proposed. Based on a numerical simulation under various conditions, automatic separation or selective clustering of micro-objects according to their sizes is performed by parallel control and programmable manipulation. This method provides efficient control of the physical variables of cells and grouping of cells with the desired size and number, which can be a milestone for a better understanding of the intercellular dynamics between clustered cells at the single-cell level for future cell-on-chip applications.

The resolution of planar-Hall magnetoresistive (PHMR) sensors was investigated in the frequency range from 0.5 Hz to 200 Hz in terms of its sensitivity, average noise level, and detectivity. Analysis of the sensor sensitivity and voltage noise response was performed by varying operational parameters such as sensor geometrical architectures, sensor configurations, sensing currents, and temperature. All the measurements of PHMR sensors were carried out under both constant current (CC) and constant voltage (CV) modes. In the present study, Barkhausen noise was revealed in 1/f noise and found less significant in the PHMR sensor configuration. under measured noise spectral density at optimized conditions, the best magnetic field detectivity was achieved better than 550 pT/√ Hz at 100 Hz and close to 1.1 nT/√ Hz at 10 Hz for a tri-layer multi-ring PHMR sensor in an unshielded environment. Furthermore, the promising feasibility and possible routes for further improvement of the sensor resolution are discussed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Data Availability Statement: All data generated or analyzed during this work are included in funded by the MSIT (No. NRF-2018R11025511) and R&D program of MOTIE (No. 20011264). funded by the MSIT (No. NRF-2018R11025511) and R&D program of MOTIE (No. 20011264).

Mesoscopic-scale effects of ferro-antiferromagnetic (F/AF) interface texture are simulated by an atomistic model, considering an exchange bias to be proportional to interfacial density of microscopic F-AF atomic coupled pairs. The model reveals a mediating role of crystalline growth direction on the exchange bias variability by other modifications of interface texture. By adjusting the number of the nearest neighboring atoms belonging to the interface plane, the growth direction defines topological possibility for exchange bias enhancement by roughness, as well as the range, within which the exchange bias can be tailored by substitutional defects. The model has been experimentally approved by investigation of exchange bias and texture modifications in a set of (0 0 1) and (1 1 1) textured NiFe/IrMn bilayers grown on Ta/Cu and Ta/Au hybrid seed layer stacks, respectively. The revealed variations of exchange bias with Au and Cu seed layer thicknesses are gradual, but have opposite signs. The result is well agreed with the simulated variability of coupling pair density for (0 0 1) and (1 1 1) interfaces. This confirms that crystallographic orientation of the F/AF interface plane sets topological possibility for tailoring the exchange bias by microscopic F-AF coupled pair density through mesoscopic modifications of the interface texture.

A facile and cost effective chemical reduction method is employed for the preparation of reduced graphene oxide/hydroxyapatite (rGO/HAp) nanocomposites. The transmission electron microscopy images revealed that the HAp flakes are well decorated on the surface of rGO. The morphological structure of the as-synthesized rGO/HAp nanocomposites was confirmed through X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy, while the composition and thermal stability were analyzed by energy dispersive spectra and thermogravimetric analysis, respectively. Furthermore, the effect of rGO/HAp nanocomposites for the proliferation of Human Mesenchymal Stem Cell (hMSC) was performed to confirm the biocompatibility. A selective chemical sensor based on rGO/HAp modified glassy carbon electrode (GCE) for sensitive detection of Bis-phenol A (BPA) has been developed. Several important parameters controlling the performance of the BPA chemi-sensor were investigated and optimized at room conditions. The rGO/HAp/Nafion/GCE sensor offers a fast response and highly sensitive BPA detection. Under the optimal conditions, a linear range from 0.2 nmol L−1 to 2.0 mmol L−1 for the detection of BPA was observed with the detection limit of 60.0 pmol L−1 (signal-to-noise ratio, at an SNR of 3) and sensitivity of 18.98 × 104 μA.L/μmol.m2. Meanwhile, the fabricated chemi-sensor showed an excellent, specific and selective recognition to target BPA molecules among coexistence of other analytes in the buffer system. This novel effort initiated a well-organized way of efficient rGO/HAp/Nafion/GCE sensor development and practically analyzed the real hazardous environmental pollutants at room conditions.

Gold nanostructures (GNs) modified electrode, which was fabricated by simple, cost–effective one–step electrochemical technique, was used for the development of an electrochemical immunosensor for the detection of CA125 antigen. The morphology of the GNs modified electrodes was easily controlled by changing the pH of the source gold electrolyte and the electrodeposition time. The GNs electrode has shown excellent electrochemical performance compared with flat bare Au electrode. Hence, the GNs electrode was used for the fabrication electrochemical immunosensor. The immobilization and sensing properties of the GNs modified bioelectrode is characterized by cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry with Fe(CN)63−/4− as an electrochemical redox indicator. The developed GNs based electrochemical immunosensor offers good response for the detection of CA125 antigen with a linear range (10–100 U mL−1), low detection limit (5.5 U mL−1). Thus, the fabricated immunosensor have potential applications as an enhance biosensing platform for biomolecules immobilization and detection.

Polyethylene glycol mediated reduced graphene oxide/zinc oxide (r-GO/ZnO) nanocomposites were synthesized by simple and cost-effective chemical reduction method using graphene oxide and zinc acetate as the precursors. The crystalline structure, morphology and thermal decomposition of the as-prepared r-GO/ZnO nanocomposites were characterized by X-ray diffraction, transmission electron microscopy and thermogravimetric analysis, respectively. Elemental composition was analyzed by energy dispersive spectra and mapping. A selective 2-nitrophenol (2-NP) sensor onto glassy carbon electrode (GCE) was fabricated with a thin-layer of synthesized r-GO/ZnO composites. Improved electrochemical responses with high sensitivity including large dynamic range and long-term stability towards the selective 2-NP were acquired using the fabricated r-GO/ZnO/GCE sensor. The calibration curve was found linear ( r 2 : 0.9916) over a wide range of 2-NP concentrations (10.0 nM–10.0 mM). The detection limit and the sensitivity were calculated as 0.27 nM and 5.8 μA·mM − 1 cm − 2 respectively based on 3 N/S (Signal-to-Noise ratio). In this approach, 2-NP was detected by I-V method using r-GO/ZnO composites modified GCE electrode with very high sensitivity compared to various nanocomposites reported earlier. The synthesis of r-GO/ZnO composites using chemical reduction process is a good way of establishing sensor based r-GO/ZnO composites for toxic and carcinogenic chemicals.

We synthesized three types of magnetic nanowires (Co-Ni-P, Co-Pt-P, and Co-Fe-P) by electrochemical deposition in polycarbonate membranes for use in magnetic barcodes. The nanowires were about 50 nm in diameter and 6 μm in length. The Co-Pt-P nanowires had the highest coercivity and remanence. We used finite elements to calculate the spatial distribution of the stray magnetic fields produced by the barcodes. The Co-Pt-P had the greatest spatial variation which makes it the best composition for the hard magnetic segment of barcode nanowires. These barcode nanowires may be used for magnetic multiplexing detection.

Core/shell nanostructures of MNPs/inorganic materials have attracted enormous research interest due to their promising applications in bio-medicine, energy, electronics, the environment, etc. Although several approaches are available for the synthesis of these core/shell nanostructures, the use of large quantities of surfactants, multi-step synthesis procedures and long reaction times still remain as challenges to be overcome for industrial applications. In this study, a novel one-pot sonochemical approach was developed for the synthesis of core/shell iron oxide/silica and iron oxide/carbon nanostructures in aqueous medium. Interestingly, the total reaction time for the synthesis of the core/shell nanostructures is found to be shorter than for other reported methods. Moreover, transmission electron microscopy indicated that the sonochemical technique produces a uniform core/shell with a highly crystalline cubic structure. However, rod-like shaped nanostructures were obtained in the absence of ultrasound. The biocompatibility of the Fe3O4/SiO2 and Fe3O4/C nanocubes and nanorods was investigated and compared with iron oxide nanostructures in in vitro quantification of TK-6 and THP-1 cell viability using a CCK-8 assay.

Programmable delivery of biological matter is indispensable for the massive arrays of individual objects in biochemical and biomedical applications. Although a digital manipulation of single cells has been implemented by the integrated circuits of micromagnetophoretic patterns with current wires, the complex fabrication process and multiple current operation steps restrict its practical application for biomolecule arrays. Here, a convenient approach using multifarious transit gates is proposed, for digital manipulation of biofunctionalized microrobotic particles that can pass through the local energy barriers by a time-dependent pulsed magnetic field instead of multiple current wires. The multifarious transit gates including return, delay, and resistance linear gates, as well as dividing, reversed, and rectifying T-junction gates, are investigated theoretically and experimentally for the programmable manipulation of microrobotic particles. The results demonstrate that, a suitable angle of the gating field at a suitable time zone is crucial to implement digital operations at integrated multifarious transit gates along bifurcation paths to trap microrobotic particles in specific apartments, paving the way for flexible on-chip arrays of biomolecules and cells.

The manipulation of superparamagnetic beads has attracted various lab on a chip and magnetic tweezer platforms for separating, sorting, and labeling cells and bioentities, but the irreversible aggregation of beads owing to magnetic interactions has limited its actual functionality. Here, an efficient solution is developed for the disaggregation of magnetic beads and interparticle distance control with a magnetophoretic decoupler using an external rotating magnetic field. A unique magnetic potential energy distribution in the form of an asymmetric magnetic thin film around the gap is created and tuned in a controlled manner, regulated by the size ratio of the bead with a magnetic pattern. Hence, the aggregated beads are detached into single beads and transported in one direction in an array pattern. Furthermore, the simultaneous and accurate spacing control of multiple magnetic bead pairs is performed by adjusting the angle of the rotating magnetic field, which continuously changes the energy well associated with a specific shape of the magnetic patterns. This technique offers an advanced solution for the disaggregation and controlled manipulation of beads, can allow new possibilities for the enhanced functioning of lab on a chip and magnetic tweezers platforms for biological assays, intercellular interactions, and magnetic biochip systems., This study reports the real‐time disaggregation and interdistance control of the magnetic beads using magnetophoretic decoupler fabricated with permalloy thin film pattern. The application of a rotating magnetic field creates a unique magnetic potential energy distribution around the decoupler at multiple points, and thus, separates the aggregated beads and transported them on the pattern to the desired direction.

CoFe2O4 and Fe3O4 nanoparticles with controllable morphology were synthesized using a convenient and facile one-pot thermal decomposition method. Iron(III) acetylacetonate and cobalt(II) acetylacetonate were used as precursors instead of the toxic and expensive pentacarbonyl, and oleic acid and oleylamine employed as solvents, stabilizers, and reducing agents. The nanoparticles exhibit well-defined shapes of varying size and their morphology can be tuned by modifying the reaction time, solvent, and temperature. Transmission electron microscopy, energy dispersive spectroscopy and X-ray diffraction were utilized to confirm the unique morphology, high crystallinity, composition and pure phase structure. Magnetic characterization of the nanoparticles further revealed the highest saturation magnetization value of 80.93 and 92.94 emu per g obtained for the cubic shape in the case of both CoFe2O4 and Fe3O4, respectively.

We demonstrate a separation method for complex mixture of superparamagnetic beads using half-disk pathways, under an in-plane rotating magnetic field, which is highly sensitive to the bead size and magnetic susceptibility. The non-linear dynamics of the beads moving along the half-disk pathways at multiple frequencies can be divided into three regimes: a phase-locked regime at low driving frequencies, a phase-slipping regime above the first critical frequency f c1 , and a phase-insulated regime above the second critical frequency f c2 in which the beads just hop at the gaps between two half-disks. Hence, based on the dynamical motions, the beads with varied sizes or heterogenic magnetic properties can be separated efficiently. Furthermore, a bio-selective separation of bead plus human monocytic leukemia (THP-1) cell complexes from bare beads has been achieved due to the increased drag force on the complexes, resulting in a decreased critical frequency.

Herein, a novel temperature sensor is proposed employing a planar Hall resistance (PHR) magnetic sensor, a magnet sheet, and an expanding polymer. It features a tunable temperature range, high linear sensitivity, accuracy, and cycling stability through 1000 cycles, and no thermal hysteresis. This new sensor is promising as a body temperature sensor.

Monodisperse Mn x Zn 1− x Fe 2 O 4 ( x = 0.2, 0.5 and 0.8) nanoparticles have been synthesized using two different routes namely sonochemical and polyol methods, and the shape and size along with physiochemical properties of the nanoparticles were compared in detail. In both the routes, the synthesis was performed in a single reaction without the use of any surfactant and deoxygenated conditions. The reaction kinetics and surface adsorption characteristics of nanoparticles were observed by thermogravimetric analysis and Fourier transform infrared spectroscopy measurements. X-ray diffraction patterns confirmed the formation of a pure ferrite phase with cubic spinel structure, and the patterns further clearly indicate that the sonochemical method produces highly crystalline particles without any post calcination reaction, comparing with the polyol process. Transmission electron microscopy results reveal that the nanoparticles synthesized by polyol method are mostly aggregated and spherical in nature whereas the nanoparticles produced by sonochemical method are monodisperse large particles with cubic like shapes. The overall studies demonstrated that the sonochemical method is facile, reliable, rapid and very attractive for the aqueous synthesis of highly crystalline and high magnetic moment (84.5 emu/g) monodisperse superparamagnetic Mn–Zn ferrite nanoparticles which considered as potential materials for various applications.

In the present study, we developed a facile approach for synthesis of high magnetic moment monodisperse Fe/ferrite and FeCo/ferrite core/shell nanoparticles. Fe 3 O 4 and CoFe 2 O 4 nanoparticles were at first synthesized through sonochemical process, followed by thermal annealing in presence of hydrogen (H 2 ) gas for 2 h for reduction into Fe and FeCo nanoparticles, respectively. Then, oxidation of Fe and FeCo nanoparticles up to 48 h in air atmosphere resulted in complete formation of Fe/ferrite and FeCo/ferrite core/shell nanostructures. Different analytical techniques such as X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy and vibrating sample magnetometer were used to characterize and confirm the successful formation of the core/shell nanostructures. In view of the obtained high magnetic Fe or FeCo core and biocompatible ferrite shell, these core–shell Fe/ferrite and FeCo/ferrite nanoparticles are expected to be promising materials for various bio-sensing applications.

A novel and efficient chemical approach for the synthesis of Fe

We developed a new one-pot synthesis method for realizing silver coated magnetite nanocomposite by way of a modified polyol process. In this reaction, polyethylene glycol was used as a solvent media and it was observed to play a key role to act as a reducing agent, stabilizer as well as a linker for silver coating simultaneously. Further, we could successfully transfer the phase from Fe3O4/Ag to α-Fe/Ag by using the annealing system at 600 °C in presence of hydrogen gas. X-ray diffraction data was independently used to confirm the formation of both the phases of Fe3O4/Ag and α-Fe/Ag. These Fe3O4/Ag and α-Fe/Ag samples were also characterized using transmission electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy techniques and compared the results with those of seed Fe3O4 nanoparticles. The magnetic properties of the composites, Fe3O4/Ag and α-Fe/Ag with different Ag concentrations, along with the seed Fe3O4 nanoparticles were measured using vibrating sample magnetometer (VSM) at room temperature. Maximum magnetization values of 61.3 emu/g and 175.1 emu/g were observed for the samples with 1 mL Ag concentrations of Fe3O4/Ag and α-Fe/Ag, respectively. This new synthesis method looks to be a promising route for facile synthesis of different magnetic nanocomposites suitable for bioapplications.