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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.

Simple Summary The development of new approaches in the field of drug delivery systems is primarily based on increasing the accuracy and precision of the targeted site and improving the stability of the drug by preventing the phagocytosis process inside the body. Among many other methods used to fulfill the above-mentioned requirements, the use of magnetotactic bacteria (MTB) is proven to be a promising solution, as it is self-propelling in nature, and can also be controlled by an external magnetic field. For the present work, we developed an MTB/PEG–biotin complex by exploiting the process of covalent bond formation between bacteria and a biotin–PEG–NHS polymer. In addition to this, attachment efficacy and stability were also determined. In biological applications, cytotoxicity assay of THP-1 cells was performed, showing the MTB/PEG–biotin complex to be less harmful to the cells; meanwhile, to explore the stealth properties of the complex, we performed a cell association assay. With these results, we provide a significant contribution to the field of potential drug delivery system development. Abstract The early removal of drug delivery agents before reaching the affected target remains an area of interest to researchers. Several magnetotactic bacteria (MTB) have been used as self-propelled drug delivery agents, and they can also be controlled by an external magnetic field. By attaching the PEG–biotin polymer, the bacteria are turned into a stealth material that can escape from the phagocytosis process and reach the area of interest with the drug load. In the study, we developed a potential drug carrier by attaching the PEG–biotin to the MTB-through-NHS crosslinker to form a MTB/PEG–biotin complex. The attachment stability, efficacy, and bacterial viability upon attachment of the PEG–biotin polymer were investigated. Biological applications were carried out using a cytotoxicity assay of THP-1 cells, and the results indicate that the MTB/PEG–biotin complex is less harmful to cell viability compared to MTB alone. Along with cytotoxicity, an assay for cell association was also evaluated to assess the complex as a potential stealth material. The development of these complexes focuses on an easy, time-saving, and stable technique of polymer attachment with the bacteria, without damaging the cell’s surface, so as to make it a strong and reliable delivery agent.

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.

The limited memory capacity of mobile devices leads to the popular use of compressed swap schemes, which reduce the I/O operations involving the swapping in and out of infrequently accessed pages. However, most of the current compressed swap schemes indiscriminately compress and store all swap-out pages. Considering that both energy and computing power are scarce resources in mobile devices, and modern applications frequently deal with already-compressed multimedia data, this blind approach may cause adverse impacts. In addition, they focus only on anonymous pages and not on file-mapped pages, because the latter are backed by on-disk files. However, our observations revealed that, in mobile devices, file-mapped pages consume significantly more memory than anonymous pages. Last but not least, most of the current compressed swap schemes blindly follow the least-recently-used (LRU) discipline when choosing the victim pages for replacement, not considering the compression ratio or data density of the cached pages. To overcome the aforementioned problems and maximize the memory efficiency, we propose a compressed swap scheme, called enhanced zswap (ezswap), for mobile devices. ezswap accommodates not only anonymous pages, but also clean file-mapped pages. It estimates the compression ratio of incoming pages with their information entropy, and selectively compresses and caches the pages only with beneficial compression ratios. In addition, its admission control and cache replacement algorithms are based on a cost-benefit model that considers not only the access recency of cached pages but also their information density and expected eviction cost. The proposed scheme was implemented in the Linux kernel for Android. Our evaluation with a series of commercial applications demonstrated that it reduced the amount of flash memory read by up to 55%, thereby improving the application launch time by up to 22% in comparison to the original zswap.

In article number 2100532, Sri Ramulu Torati, CheolGi Kim, and co‐workers develop the magnetophoretic decoupler for the disaggregation and inter‐particle distance control of magnetic bead cluster for higher efficiency of bio‐carrier role. This magnetophoretic decoupler can split the multiple bead pairs in different directions using single driving force, and linearly control the inter‐particle distance between them through the angle of the external field. [Image: see text]

Advanced microelectromechanical system (MEMS) magnetic field sensor applications demand ultra-high detectivity down to the low magnetic fields. To enhance the detection limit of the magnetic sensor, a resistance compensator integrated self-balanced bridge type sensor was devised for low-frequency noise reduction in the frequency range of 0.5 Hz to 200 Hz. The self-balanced bridge sensor was a NiFe (10 nm)/IrMn (10 nm) bilayer structure in the framework of planar Hall magnetoresistance (PHMR) technology. The proposed resistance compensator integrated with a self-bridge sensor architecture presented a compact and cheaper alternative to marketable MEMS MR sensors, adjusting the offset voltage compensation at the wafer level, and led to substantial improvement in the sensor noise level. Moreover, the sensor noise components of electronic and magnetic origin were identified by measuring the sensor noise spectral density as a function of temperature and operating power. The lowest achievable noise in this device architecture was estimated at ~3.34 nV/Hz at 100 Hz.

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).