Magnetic Manipulation System Research Articles

Three-Dimensional Magnetic Manipulation of Micro- and Nanostructures for Applications in Life Sciences

We present a magnetic manipulation system capable of 5 degree-of-freedom (5-DOF) wireless control of micro- and nanostructures (3-DOF position, 2-DOF pointing orientation). The system has a spherical workspace with a diameter of approximately 10 mm, and is completely unrestrained in the rotational degrees-of-freedom. This is accomplished through the superposition of multiple magnetic fields, and capitalizes on a linear representation of the coupled field contributions of multiple soft-magnetic-core electromagnets acting in concert. The system consists of 8 stationary electromagnets with ferromagnetic cores, and is capable of producing arbitrary magnetic fields and field gradients up to 50 mT and 5 T/m at frequencies up to 2 kHz. The capabilities of the system are evaluated through the introduction of the reachable magnetic workspace of the system as well as frequency response and calibration results. Experimental results are presented which demonstrate different magnetic control strategies at sub-mm and sub-μm scale.

Graphite Coating of Iron Nanowires for Nanorobotic Applications: Synthesis, Characterization and Magnetic Wireless Manipulation

AbstractWireless‐manipulated graphite coated nanomagnets are promising candidates for minimally invasive targeted drug delivery platforms. Iron nanowires coated with graphitic shells are synthesized by template‐assisted deposition. The use of porous aluminum oxide templates enables both the batch production of nanowires by electrodeposition and their subsequent conformal encapsulation in graphite using chemical vapor deposition (CVD). High quality graphitic shells are obtained when CVD conditions are optimized using acetylene as carbon feedstock at 740 °C. Interestingly, the iron nanowires transform into iron carbide during the CVD process leading to changes in magnetic properties. The graphite coated iron nanowires are precisely manipulated against a water flow (0.1 mm/s) using a magnetic field of 350 Oe and a gradient of 50 kOe m−1 in a 5‐DOF magnetic manipulation system. Our approach opens new avenues for the design and synthesis of functional graphite coated nanowires that are promising for nanorobotics applications.

A Magnetic Manipulation System Using an Active Filter for Electronic Detection of Target Cells

Important advances in the development of magnetic manipulation devices have been recorded over the last few years and promising experimental results have been presented. In this article we first perform a detailed analysis on one of most widely used magnetic actuators, namely a planar microcoil. Key parameters that affect the performance of the actuator are identified and our results are in accordance with measured data. Making use of these findings, a lab-on-a-chip system is proposed, that also integrates a novel electronic sensing concept for live monitoring of its activity. Possible applications of this system include highly selective bioseparation or the possibility to manipulate and assemble marked particles with great precision.

A magnetic resonance (MR) compatible selective brain temperature manipulation system for preclinical study

There is overwhelming evidence that hypothermia can improve the outcome of an ischemic stroke. However, the most widely used systemic cooling method could lead to multiple side effects, while the incompatibility with magnetic resonance imaging of the present selective cooling methods highly limit their application in preclinical studies. In this study, we developed a magnetic resonance compatible selective brain temperature manipulation system for small animals, which can regulate brain temperature quickly and accurately for a desired period of time, while maintaining the normal body physiological conditions. This device was utilized to examine the relationship between T1 relaxation, cerebral blood flow, and temperature in brain tissue during magnetic resonance imaging of ischemic stroke. The results showed that this device can be an efficient brain temperature manipulation tool for preclinical studies needing local hypothermic or hyperthermic conditions.

On-chip antibody handling and colorimetric detection in a magnetic droplet manipulation system

Miniaturized system for bioanalysis have been constantly gaining importance and interest within the recent years. The reduction of sample consumption and reaction time are some of the major advantages of such lab-on-a-chip applications. One of the greatest challenges in these systems is the handling of small sample volumes. A possible way is to manipulate such volumes in the form of small droplets. This work demonstrates the potential of a modular magnetic droplet manipulation system for its application in bioanalysis. We studied the parameters of the droplet manipulation, and their application for the on-chip detection of an enzyme labeled antibody. By using sample volumes of μl size we are able to detect quantities in the pg-range of enzyme labeled antibodies, which is the first step to a miniaturized immunoassay on a chip.

Thin-foil magnetic force system for high-numerical-aperture microscopy.

Forces play a key role in a wide range of biological phenomena from single-protein conformational dynamics to transcription and cell division, to name a few. The majority of existing microbiological force application methods can be divided into two categories: those that can apply relatively high forces through the use of a physical connection to a probe and those that apply smaller forces with a detached probe. Existing magnetic manipulators utilizing high fields and high field gradients have been able to reduce this gap in maximum applicable force, but the size of such devices has limited their use in applications where high force and high-numerical-aperture (NA) microscopy must be combined. We have developed a magnetic manipulation system that is capable of applying forces in excess of 700 pN on a 1 mum paramagnetic particle and 13 nN on a 4.5 mum paramagnetic particle, forces over the full 4pi sr, and a bandwidth in excess of 3 kHz while remaining compatible with a commercially available high-NA microscope objective. Our system design separates the pole tips from the flux coils so that the magnetic-field geometry at the sample is determined by removable thin-foil pole plates, allowing easy change from experiment to experiment. In addition, we have combined the magnetic manipulator with a feedback-enhanced, high-resolution (2.4 nm), high-bandwidth (10 kHz), long-range (100 mum xyz range) laser tracking system. We demonstrate the usefulness of this system in a study of the role of forces in higher-order chromosome structure and function.

Three-dimensional force microscope: A nanometric optical tracking and magnetic manipulation system for the biomedical sciences

We report here the development of a three-dimensional (3D) magnetic force microscope for applying forces to and measuring responses of biological systems and materials. This instrument combines a conventional optical microscope with a free-floating or specifically bound magnetic bead used as a mechanical probe. Forces can be applied by the bead to microscopic structures of interest (specimens), while the reaction displacement of the bead is measured. This enables 3D mechanical manipulations and measurements to be performed on specimens in fluids. Force is generated by the magnetically permeable bead in reaction to fields produced by external electromagnets. The displacement is measured by interferometry using forward light scattered by the bead from a focused laser beam. The far-field interference pattern is imaged on a quadrant photodetector from which the 3D displacement can be computed over a limited range about the focal point. The bead and specimen are mounted on a 3D translation stage and feedback techniques are used to keep the bead within this limited range. We demonstrate the system with application to beads attached to cilia in human lung cell cultures.

Three-dimensional force microscope: A nanometric optical tracking and magnetic manipulation system for the biomedical sciences

Three-dimensional force microscope: A nanometric optical tracking and magnetic manipulation system for the biomedical sciences

Magnetic manipulation instrumentation for medical physics research

The noncontact magnetic manipulation of probe masses within the body is an area of research that has received substantial attention from the medical physics community, especially during the past three decades. The therapeutic and diagnostic possibilities arising from such technology include site-specific drug delivery within the central nervous system, advancement of techniques for navigation and selective catheterization of vessels within the cardiovascular and cerebrovascular systems, and the nonsurgical exploration of the alimentary and respiratory tracts. In this review, we examine the physical principles underlying in vivo magnetic manipulation systems, and catalog the various types of instrumentation used for such purposes to date. Thereafter, we evaluate the different methods of image-based localization used to identify the position of the probe within the body. Finally, we appraise an emerging technology known as nonlinear magnetic stereotaxis, a technique that permits minimally invasive access to difficult-to-approach parts of the brain. We close the review with a few comments on the directions for future work within this field.