Micro- and Nanostructure Motion with Magnetic Fields (original) (raw)

Rotational Maneuver of Ferromagnetic Nanowires for Cell Manipulation

IEEE Transactions on NanoBioscience, 2000

1-D magnetic nanowires provide a powerful tool for investigating biological systems because such nanomaterials possess unique magnetic properties, which allow effective manipulation of cellular and subcellular objects. In this study, we report the rotational maneuver of ferromagnetic nanowires and their applications in cell manipulation. The rotational maneuver is studied under two different suspension conditions. The rotation of nanowires in the fluid is analyzed using Stokes flow assumption. Experimental results show that when the nanowires develop contacts with the bottom surfaces, the rotational maneuver under a modest external magnetic field can generate rapid lateral motion. The floating nanowires, on the other hand, do not exhibit substantial lateral displacements. Cell manipulation using skeletal myoblasts C2C12 shows that living cells can be manipulated efficiently on the bottom surface by the rotational maneuver of the attached nanowires. We also demonstrate the use of rotational maneuver of nanowires for creating 3-D nanowire clusters and multicellular clusters. This study is expected to add to the knowledge of nanowire-based cell manipulation and contribute to a full spectrum of control strategies for efficient use of nanowires for micro-total-analysis. It may also facilitate mechanobiological studies at cellular level, and provide useful insights for development of 3-D in vivo-like multicellular models for various applications in tissue engineering.

1 Magneto-mechanical coupling of single domain particles in soft matter systems

Magnetic Hybrid-Materials

Combining inorganic magnetic particles with complex soft matrices such as liquid crystals, biological fluids, gels, or elastomers, allows access to a plethora of magnetoactive effects that are useful for sensing and actuation perspectives, allowing inter alia to explore and manipulate material properties on the nanoscale. The article provides a comprehensive summary of recent advancement on employing magnetic nanoparticles either as tracers for dynamic processes, or as nanoscopic actuating units. By variation of the particle characteristics in terms of size, shape, surface functionality, and magnetic behavior, the interaction between the probe or actuator particles and their environment can be systematically tailored in wide ranges, giving insight into the relevant structure-property relationships.

Paramagnetic microparticles sliding on a surface: Characterization and closed-loop motion control

2015 IEEE International Conference on Robotics and Automation (ICRA), 2015

In targeted therapy, clusters of drug carriers (nanoparticles and microparticles) could be in contact with a surface such as the lumen of blood vessels and the interior of the gastrointestinal tract. We study the motion characteristics of clusters of microparticles when they slide on a surface under the influence of weak oscillating magnetic fields (less than 11 mT). The oscillating magnetic fields exert a magnetic torque on the microparticles and allow them to oscillate, and hence overcome the static friction and slide on a surface. We characterize the frequency response of clusters of microparticles by applying oscillating magnetic fields with a frequency range of 0 Hz to 55 Hz, in the presence of a constant magnetic field gradient (0.9 T/m). Clusters of 3 to 4 and 5 to 9 microparticles achieve maximum sliding speeds of 1100 µm/s and 1150 µm/s, at oscillating magnetic fields of 30 Hz. In addition, we experimentally demonstrate closed-loop motion control of the clusters with maximum position error of 20 µm. Furthermore, we show that the magnetic field gradient required to drive a cluster of microparticles (with 3 to 4 microparticles) decreases by 75% in the presence of oscillating magnetic fields from 5 Hz to 50 Hz.

Magnetic micropillars as a tool to govern substrate deformations

Lab on a Chip, 2011

Magnetic actuated microdevices can be used to achieve several complex functions in microfluidics and microfabricated devices. For example, magnetic mixers and magnetic actuators have been proposed to help handling fluids at a small scale. Here, we present a strategy to create magnetically actuated micropillar arrays. We combined microfabrication techniques and the dispersion of magnetic aggregates embedded inside polymeric matrices to design micrometre scale magnetic features. By creating a magnetic field gradient in the vicinity of the substrate, well-defined forces were applied on these magnetic aggregates which in turn induced a deflection of the micropillars. By dispersing either spherical aggregates or magnetic nanowires into the gels, we can induce synchronized motions of a group of pillars or the movement of isolated pillars under a magnetic field gradient. When combined with microfabrication processes, this versatile tool leads to local as well as global substrate actuations within a range of dimensions that are relevant for microfluidics and biological applications.

Autonomously Moving Local Nanoprobes in Heterogeneous Magnetic Fields

Journal of Physical Chemistry C, 2007

Different strategies of navigation in heterogeneous magnetic fields are investigated using natural and synthetic autonomously moving micro-and nanonavigators on top of a magnetic garnet film with uniaxial anisotropy creating a dense stripe domain structure. The use of ferromagnetic navigators leads to dynamic frustration, but synergy is achieved between the autonomous motion and magnetic orientation of paramagnetic navigators. The use of differently magnetized ferromagnetic and paramagnetic nanonavigators enables one to change from a roving to a guided motion. These different modes of motion can be utilized for distinct processes, such as the delivery and distribution of molecular cargo attached to synthetic navigators.

Dynamics of paramagnetic nanostructured rods under rotating field

The dynamical rotational behavior of magnetic nanostructured rods based on the auto-association of maghemite nanoparticles and block-copolymers is probed by optical microscopy under rotating fields in a simple liquid. The re-orientation of the rods by a field rotated by 901 is first studied. The measured relaxation is characteristic of paramagnetic objects. Under a stationary rotating field, a synchronous rotational regime is observed at low field frequency. Above a frequency threshold which scales as H 2 , the dynamics becomes asynchronous with back-and-forth rotations. These behaviors are well predicted by the presented model.

Recent developments in magnetically driven micro- and nanorobots

Applied Materials Today

Micro-and nanorobots are promising devices for biomedical and environmental applications. The past few years have witnessed rapid developments in this field. This short review intends to address recent progress on magnetically driven micro-and nanorobots developed in our laboratory and by other research groups. Different designs such as helical swimmers, flexible swimmers, surface walkers, and others are categorized and discussed. Specific applications of these robots in the fields of biomedicine or environmental remediation are also reported. Finally, the use of magnetic fields for additional capabilities beyond manipulation is presented.