共查询到20条相似文献,搜索用时 78 毫秒
1.
Xinghao Hu Sri Ramulu Torati Hyeonseol Kim Jonghwan Yoon Byeonghwa Lim Kunwoo Kim Metin Sitti CheolGi Kim 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(28)
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. 相似文献
2.
Julia M. McCoey Robert W. de Gille Babak Nasr Jean‐Philippe Tetienne Liam T. Hall David A. Simpson Lloyd C. L. Hollenberg 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(18)
Magnetic microparticles or “beads” are used in a variety of research applications from cell sorting through to optical force traction microscopy. The magnetic properties of such particles can be tailored for specific applications with the uniformity of individual beads critical to their function. However, the majority of magnetic characterization techniques quantify the magnetic properties from large bead ensembles. Developing new magnetic imaging techniques to evaluate and visualize the magnetic fields from single beads will allow detailed insight into the magnetic uniformity, anisotropy, and alignment of magnetic domains. Here, diamond‐based magnetic microscopy is applied to image and characterize individual magnetic beads with varying magnetic and structural properties: ferromagnetic and superparamagnetic/paramagnetic, shell (coated with magnetic material), and solid (magnetic material dispersed in matrix). The single‐bead magnetic images identify irregularities in the magnetic profiles from individual bead populations. Magnetic simulations account for the varying magnetic profiles and allow to infer the magnetization of individual beads. Additionally, this work shows that the imaging technique can be adapted to achieve illumination‐free tracking of magnetic beads, opening the possibility of tracking cell movements and mechanics in photosensitive contexts. 相似文献
3.
The growth of the biopharmaceutical industry has created a demand for new technologies for the purification of genetically engineered proteins.The efficiency of large-scale, high-gradient magnetic fishing could be improved if magnetic particles offering higher binding capacity and magnetization were available. This article describes several strategies for synthesizing microbeads that are composed of a M13 bacteriophage layer assembled on a superparamagnetic core. Chemical cross-linking of the pVIII proteins to a carboxyl-functionalized bead produces highly responsive superparamagnetic particles (SPM) with a side-on oriented, adherent virus monolayer. Also, the genetic manipulation of the pIII proteins with a His(6) peptide sequence allows reversible assembly of the bacteriophage on a nitrilotriacetic-acid-functionalized core in an end-on configuration. These phage-magnetic particles are successfully used to separate antibodies from high-protein concentration solutions in a single step with a >90% purity. The dense magnetic core of these particles makes them five times more responsive to magnetic fields than commercial materials composed of polymer-(iron oxide) composites and a monolayer of phage could produce a 1000 fold higher antibody binding capacity. These new bionanomaterials appear to be well-suited to large-scale high-gradient magnetic fishing separation and promise to be cost effective as a result of the self-assembling and self-replicating properties of genetically engineered M13 bacteriophage. 相似文献
4.
Although strong magnetic fields cannot be conveniently “focused” like light, modern microfabrication techniques enable preparation of microstructures with which the field gradients – and resulting magnetic forces – can be localized to very small dimensions. This ability provides the foundation for magnetic tweezers which in their classical variant can address magnetic targets. More recently, the so‐called negative magnetophoretic tweezers have also been developed which enable trapping and manipulations of completely nonmagnetic particles provided that they are suspended in a high‐magnetic‐susceptibility liquid. These two modes of magnetic tweezing are complimentary techniques tailorable for different types of applications. This Progress Report provides the theoretical basis for both modalities and illustrates their specific uses ranging from the manipulation of colloids in 2D and 3D, to trapping of living cells, control of cell function, experiments with single molecules, and more. 相似文献
5.
Yalan Zhang Yu Wang Huan Wang Ying Yu Qifeng Zhong Yuanjin Zhao 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(35)
Structural color hydrogels are promising candidates as scaffold materials for tissue engineering and for matrix cell culture and manipulation, while their super‐elastic features are still lacking due to the irreconcilable interfere of the precursor and the self‐assembly unit. This hinders many of their practical biomedical applications where elasticity is required. Herein, hydrophilic and size‐controllable Fe3O4@poly(4‐styrenesulfonic acid‐co‐maleic acid) (PSSMA)@SiO2 magnetic response photonic crystals are fabricated as the assembly units of the structural color hydrogels by orderly packing of core–shell colloidal nanocrystal clusters via a two‐step facile synthesis approach. These units are capable of responding instantaneously to an external magnetic field with resistance to interference of ions, thus, by integrating super‐elastic hydrogels, super‐elastic magnetic structural color hydrogels can be achieved. The structural color arises from the dynamic ordering of the magnetic nanoparticles through the contactless control of external magnetic field, allowing regional polymerization of hydrogels via changing orientation and strength of external magnetic field. These regionally polymerized super‐elastic magnetic structural color hydrogels can work as anti‐counterfeiting labels with super‐elastic identification, which may be widely used in the future. 相似文献
6.
We have investigated and modeled the effect of interaction among magnetic particles and the magnitude and duration of external applied magnetic field on Brownian relaxation in a colloidal suspension. In the case of interacting magnetic particles, Brownian relaxation depends on the interparticle dipole-dipole interaction, which slows down the overall Brownian relaxation process of magnetic particles in the colloidal suspension. The individual magnetic particle experiences torque when a pulsatile magnetic field is applied. The torque due to the external field randomizes the particle rotation similar to that of the thermal energy. A faster Brownian relaxation is observed when individual magnetic particles are magnetized for a short duration. Magnetizing the magnetic particle for a longer duration suppress the rotational motion hence the effect of torque on Brownian relaxation. 相似文献
7.
Frederik W. Østerberg Giovanni Rizzi Marco Donolato Rebecca S. Bejhed Anja Mezger Mattias Strömberg Mats Nilsson Maria Strømme Peter Svedlindh Mikkel F. Hansen 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(14):2877-2882
For the first time DNA coils formed by rolling circle amplification are quantified on‐chip by Brownian relaxation measurements on magnetic nanobeads using a magnetoresistive sensor. No external magnetic fields are required besides the magnetic field arising from the current through the sensor, which makes the setup very compact. Limits of detection down to 500 Bacillus globigii spores and 2 pM of Vibrio cholerae are demonstrated, which are on the same order of magnitude or lower than those achieved previously using a commercial macro‐scale AC susceptometer. The chip‐based readout is an important step towards the realization of field tests based on rolling circle amplification molecular analyses. 相似文献
8.
Michael K. Hausmann Alina Hauser Gilberto Siqueira Rafael Libanori Signe Lin Vehusheia Simone Schuerle Tanja Zimmermann Andr R. Studart 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(1)
Responsive materials with birefringent optical properties have been exploited for the manipulation of light in several modern electronic devices. While electrical fields are often utilized to achieve optical modulation, magnetic stimuli may offer an enticing complementary approach for controlling and manipulating light remotely. Here, the synthesis and characterization of magnetically responsive birefringent microparticles with unusual magneto‐optical properties are reported. These functional microparticles are prepared via a microfluidic emulsification process, in which water‐based droplets are generated in a flow‐focusing device and stretched into anisotropic shapes before conversion into particles via photopolymerization. Birefringence properties are achieved by aligning cellulose nanocrystals within the microparticles during droplet stretching, whereas magnetic responsiveness results from the addition of superparamagnetic nanoparticles to the initial droplet template. When suspended in a fluid, the microparticles can be controllably manipulated via an external magnetic field to result in unique magneto‐optical coupling effects. Using a remotely actuated magnetic field coupled to a polarized optical microscope, these microparticles can be employed to convert magnetic into optical signals or to estimate the viscosity of the suspending fluid through magnetically driven microrheology. 相似文献
9.
Zengguang Cheng Carlos Ríos Nathan Youngblood C. David Wright Wolfram H. P. Pernice Harish Bhaskaran 《Advanced materials (Deerfield Beach, Fla.)》2018,30(32)
Inspired by the great success of fiber optics in ultrafast data transmission, photonic computing is being extensively studied as an alternative to replace or hybridize electronic computers, which are reaching speed and bandwidth limitations. Mimicking and implementing basic computing elements on photonic devices is a first and essential step toward all‐optical computers. Here, an optical pulse‐width modulation (PWM) switching of phase‐change materials on an integrated waveguide is developed, which allows practical implementation of photonic memories and logic devices. It is established that PWM with low peak power is very effective for recrystallization of phase‐change materials, in terms of both energy efficiency and process control. Using this understanding, multilevel photonic memories with complete random accessibility are then implemented. Finally, programmable optical logic devices are demonstrated conceptually and experimentally, with logic “OR” and “NAND” achieved on just a single integrated photonic phase‐change cell. This study provides a practical and elegant technique to optically program photonic phase‐change devices for computing applications. 相似文献
10.
Magnetic Susceptibility Study of Sub‐Pico‐emu Sample Using a Micromagnetometer: An Investigation through Bistable Spin‐Crossover Materials 下载免费PDF全文
Souleymane Kamara Quang‐Hung Tran Vincent Davesne Gautier Félix Lionel Salmon Kunwoo Kim CheolGi Kim Azzedine Bousseksou Ferial Terki 《Advanced materials (Deerfield Beach, Fla.)》2017,29(46)
A promising and original method to study the spin‐transition in bistable spin‐crossover (SCO) materials using a magnetoresistive multiring sensor and its self‐generated magnetic field is reported. Qualitative and quantitative studies are carried out combining theoretical and experimental approaches. The results show that only a small part of matter dropped on the sensor surface is probed by the device. At a low bias‐current range, the number of detected nanoparticles depends on the amplitude of the current. However, in agreement with the theoretical model, the stray voltage from the particles is proportional to the current squared. By changing both the bias current and the concentration of particle droplet, the thermal hysteresis of an ultrasmall volume, 1 × 10?4 mm3, of SCO particles is measured. The local probe of the experimental setup allows a highest resolution of 4 × 10?14 emu to be reached, which is never achieved by experimental methods at room temperature. 相似文献
11.
12.
Sangwoo Shin Jesse T. Ault Jie Feng Patrick B. Warren Howard A. Stone 《Advanced materials (Deerfield Beach, Fla.)》2017,29(30)
The zeta potential is an electric potential in the Debye screening layer of an electrolyte, which represents a key physicochemical surface property in various fields ranging from electrochemistry to pharmaceuticals. Thus, characterizing the zeta potential is essential for many applications, but available measurement techniques are limited. Electrophoretic light scattering is typically used to measure the zeta potential of particles in suspension, whereas zeta potential measurements of a solid wall in solution rely on either streaming potential or electroosmotic mobility measurement techniques, both of which are expensive and sophisticated. Here, a simple, robust method to simultaneously measure the zeta potential of particles in suspension and solid walls is presented. The method uses solute gradients to induce particle and fluid motions via diffusiophoresis and diffusioosmosis, respectively, which are both sensitive to the zeta potential of the particle and the wall. By visualizing the particle dynamics, both zeta potentials can be determined independently. Finally, a compact microscope is used to demonstrate low‐cost zeta potentiometry that allows measurement of both particle and wall zeta potentials, which suggests a cost‐effective tool for pharmaceuticals as well as for educational purposes. 相似文献
13.
Yongsok Seo 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(43):2300320
A magnetorheological (MR) fluid is generally called a suspension in which magnetic particles are dispersed in a non-magnetic medium. When an external magnetic field is applied, a pseudo-phase transition occurs within a short time to generate yield stress, and when the magnetic field is released, it returns to the suspended state. Due to these unique characteristics, it is classified as a smart material to be widely applied in various industries. High performance MR fluids require high yield stress and stability for long-term use. However, it is very difficult to improve performance and stability simultaneously due to the limited amount of magnetic particles in the suspension and particle sedimentation caused by the density mismatch between the suspending particles and the liquid phase. In this study, an MR slurry is developed that is completely different from the MR suspension, starting from the opposite concept. An innovative non-settling (i.e., permanently stable) magnetorheological slurry is successfully created that exhibits unprecedented ultra-high yield stress. This result is expected to be a turning point for applying MR fluids to more diverse industries. In addition, a simple fitting equation expressing the yield stress as a function of the particle volume fraction is proposed. 相似文献
14.
Satya N. Guin Praveen Vir Yang Zhang Nitesh Kumar Sarah J. Watzman Chenguang Fu Enke Liu Kaustuv Manna Walter Schnelle Johannes Gooth Chandra Shekhar Yan Sun Claudia Felser 《Advanced materials (Deerfield Beach, Fla.)》2019,31(25)
The discovery of magnetic topological semimetals has recently attracted significant attention in the field of topology and thermoelectrics. In a thermoelectric device based on the Nernst geometry, an external magnet is required as an integral part. Reported is a zero‐field Nernst effect in a newly discovered hard‐ferromagnetic kagome‐lattice Weyl‐semimetal Co3Sn2S2. A maximum Nernst thermopower of ≈3 µV K?1 at 80 K in zero field is achieved in this magnetic Weyl‐semimetal. The results demonstrate the possibility of application of topological hard magnetic semimetals for low‐power thermoelectric devices based on the Nernst effect and are thus valuable for the comprehensive understanding of transport properties in this class of materials. 相似文献
15.
K. Han Y. T. Feng D. R. J. Owen 《International journal for numerical methods in engineering》2010,84(11):1273-1302
A magnetorheological fluid (MR fluid) is a type of smart fluid composed of micrometer‐sized magnetizable particles suspended in a carrier fluid. The rheological properties of an MR fluid can be greatly altered upon application of an external magnetic field. This paper presents a computational framework for the numerical study of MR fluids, in which a two‐stage modelling and simulation strategy is proposed to achieve reasonable accuracy and computational efficiency. At the first stage for simulating the particle chain formation, the particle dynamics plays a major role whereas the hydrodynamics of the fluid flow is of secondary importance. Thus an MR fluid is modelled in the context of the discrete element method and the simple Stokes formula is adopted for the hydrodynamic interaction. At the second stage, the formulated particle chains are applied as the initial configuration for simulating the rheological properties of the fluid under different shear loading conditions. A combined lattice Boltzmann and discrete element approach is employed to fully resolve the fluid field and the hydrodynamic interactions between the fluid and the particles. Some relevant magnetic models are comprehensively reviewed and the mutual dipole model is employed in this work to account for the magnetic interactions between the particles. The proposed solution procedure is illustrated via a set of numerical simulations for a representative volume element of an MR fluid. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
16.
Roland Fuhrer Evagelos Kimon Athanassiou Norman Albert Luechinger Wendelin Jan Stark 《Small (Weinheim an der Bergstrasse, Germany)》2009,5(3):383-388
The combination of force and flexibility is at the core of biomechanics and enables virtually all body movements in living organisms. In sharp contrast, presently used machines are based on rigid, linear (cylinders) or circular (rotator in an electrical engine) geometries. As a potential bioinspired alternative, magnetic elastomers can be realized through dispersion of micro‐ or nanoparticles in polymer matrices and have attracted significant interest as soft actuators in artificial organs, implants, and devices for controlled drug delivery. At present, magnetic particle loss and limited actuator strength have restricted the use of such materials to niche applications. We describe the direct incorporation of metal nanoparticles into the backbone of a hydrogel and application as an ultra‐flexible, yet strong magnetic actuator. Covalent bonding of the particles prevents metal loss or leaching. Since metals have a far higher saturation magnetization and higher density than oxides, the resulting increased force/volume ratio afforded significantly stronger magnetic actuators with high mechanical stability, elasticity, and shape memory effect. 相似文献
17.
Advection Flows‐Enhanced Magnetic Separation for High‐Throughput Bacteria Separation from Undiluted Whole Blood 下载免费PDF全文
Su Hyun Jung Young Ki Hahn Sein Oh Seyong Kwon Eujin Um Sungyoung Choi Joo H. Kang 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(34)
A major challenge to scale up a microfluidic magnetic separator for extracorporeal blood cleansing applications is to overcome low magnetic drag velocity caused by viscous blood components interfering with magnetophoresis. Therefore, there is an unmet need to develop an effective method to position magnetic particles to the area of augmented magnetic flux density gradients while retaining clinically applicable throughput. Here, a magnetophoretic cell separation device, integrated with slanted ridge‐arrays in a microfluidic channel, is reported. The slanted ridges patterned in the microfluidic channels generate spiral flows along the microfluidic channel. The cells bound with magnetic particles follow trajectories of the spiral streamlines and are repeatedly transferred in a transverse direction toward the area adjacent to a ferromagnetic nickel structure, where they are exposed to a highly augmented magnetic force of 7.68 µN that is much greater than the force (0.35 pN) at the side of the channel furthest from the nickel structure. With this approach, 91.68% ± 2.18% of Escherichia coli (E. coli) bound with magnetic nanoparticles are successfully separated from undiluted whole blood at a flow rate of 0.6 mL h?1 in a single microfluidic channel, whereas only 23.98% ± 6.59% of E. coli are depleted in the conventional microfluidic device. 相似文献
18.
Current‐Induced Nucleation and Annihilation of Magnetic Skyrmions at Room Temperature in a Chiral Magnet 下载免费PDF全文
Xiuzhen Yu Daisuke Morikawa Yusuke Tokunaga Takashi Kurumaji Hiroshi Oike Masao Nakamura Fumitaka Kagawa Yasujiro Taguchi Taka‐hisa Arima Masashi Kawasaki Yoshinori Tokura 《Advanced materials (Deerfield Beach, Fla.)》2017,29(21)
A magnetic skyrmion is a nanometer‐scale magnetic vortex carrying an integer topological charge. Skyrmions show a promise for potential application in low‐power‐consumption and high‐density memory devices. To promote their use in applications, it is attempted to control the existence of skyrmions using low electric currents at room temperature (RT). This study presents real‐space observations for the current‐induced formation and annihilation of a skyrmion lattice (SkL) as well as isolated skyrmions in a microdevice composed of a thin chiral magnet Co8Zn9Mn3 with a Curie temperature, T C ≈ 325 K, above RT. It is found that the critical current for the manipulation of Bloch‐type skyrmions is on the order of 108 A m?2, approximately three orders of magnitude lower than that needed for the creation and drive of ferromagnetic (FM) domain walls in thin FM films. The in situ real‐space imaging also demonstrates the dynamical topological transition from a helical or conical structure to a SkL induced by the flow of DC current, thus paving the way for the electrical control of magnetic skyrmions. 相似文献
19.
Cheng Chi Bowen Shi Cong Liu Yimin Kang Li Lin Meiling Jiang Jing Lu Bo Shen Feng Lin Hailin Peng Zheyu Fang 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(2)
Graphene has attracted great interests in various areas including optoelectronics, spintronics, and nanomechanics due to its unique electronic structure, a linear dispersion with a zero bandgap around the Dirac point. Shifts of Dirac cones in graphene creates pseudo‐magnetic field, which generates an energy gap and brings a zero‐magnetic‐field analogue of the quantum Hall effect. Recent studies have demonstrated that graphene pseudo‐magnetic effects can be generated by vacancy defects, atom adsorption, zigzag or armchair edges, and external strain. Here, a larger than 100 T pseudo‐magnetic field is reported that generated on the step area of graphene; and with the ultrahigh vacuum scanning tunneling microscopy, the observed Landau levels can be effectively tailored by graphene phonons. The zero pseudo‐Landau level is suppressed due to the phonon‐mediated inelastic tunneling, and this is observed by the scanning tunneling spectroscopy spectrum and confirmed by the Vienna ab initio simulation package calculation, where graphene phonons modulate the flow of tunneling electrons and further mediate pseudo‐Landau levels. These observations demonstrate a viable approach for the control of pseudo‐Landau levels, which tailors the electronic structure of graphene, and further ignites applications in graphene valley electronics. 相似文献
20.
Peng Zhai Yuechen Wang Chang Liu Xun Wang Shien‐Ping Feng 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(39)
This study demonstrates that the application of an external electrical potential to a phenyl‐sulfonic functionalized graphene (SG)/water suspension distinctly enhances its electrical conductivity via the structural transition from isolated clusters to a 3D SG network. Microstructural and alternating current impedance spectroscopy studies indicate that the surface charge plays an important role in the state of dispersion and connectivity of the SG in the suspension due to the potential‐dependent interactions with functional groups on the SG surface in the presence of an external electrical potential. In addition, the conductive SG/ice can be produced via liquid–solid phase transition of the SG/water suspension in the presence of an external electrical potential, which shows a one‐order magnitude improvement in electrical conductivity compared with pure ice. The electric‐field‐tunable property advances the understanding of nanofluid systems and has many potential applications. 相似文献