Optimization of force produced by electromagnet needles acting on superparamagnetic microparticles

Yu, Xingwen; Miller, J.W.; Sica, Vincent; LaVan, David A.

doi:10.1063/1.2896046

Cited by 11 publications

(6 citation statements)

References 29 publications

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“…Unidirectional force generation with single‐source far‐field tweezers (Figure a) is trivial, but does not allow easy 3D control over the target objects. To do that, two approaches have emerged: scanning magnetic micropens and magnetic multipole tweezers . The most straightforward approach is with magnetic microtips that are attached to a 3D micropositioner and the motions of the target particle are monitored with regular optical bright‐field or dark‐field techniques ( Figure a–e).…”

Section: Magnetic Tweezing Based On Positive Magnetophoresismentioning

confidence: 99%

Tweezing of Magnetic and Non‐Magnetic Objects with Magnetic Fields

Timonen

Grzybowski

2017

Advanced Materials

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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.

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Section: Magnetic Tweezing Based On Positive Magnetophoresismentioning

confidence: 99%

Tweezing of Magnetic and Non‐Magnetic Objects with Magnetic Fields

Timonen

Grzybowski

2017

Advanced Materials

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“…Since we are interested in applications of force spectroscopy in an array format, rather than micromanipulation, blunt tips and wide cores are more appropriate than sharp needles. 16 Figure 6 demonstrates that sharper tips result in a quick build up of a substantial lateral force component acting on the beads placed off-axis. Keeping the magnitude of the lateral component under ϳ5% of the total forces for the region of interest ͑50-100 m around the magnet axis͒ requires relatively blunt tips and tip curvatures of 1 to 1.5 mm tend to be the best for these purposes.…”

Section: A Effect Of Tip Length and Radiusmentioning

confidence: 99%

“…The magnetic field and forces generated by permanent magnets in various arrangements have been treated theoretically, 6,14,15 while rigorous theoretical modeling of electromagnetic tweezers has not received much attention. 16 Electromagnets are an attractive option for force generation in even the simplest of configurations ͑e.g., when force is applied in the direction normal to the plane of biomolecular attachment͒, since it is possible to control the magnetic field easily via changes in the current applied to the electromagnet coil. The ramp of the magnetic field to generate a force-extension curve using an electromagnet does not require mechanical motion ͑only variable current͒, thus, yielding better environmental noise characteristics for magnetic tweezers, while preserving a straightforward setup for force spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Quantitative modeling of forces in electromagnetic tweezers

Bijamov

Shubitidze

Oliver

et al. 2010

Journal of Applied Physics

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This paper discusses numerical simulations of the magnetic field produced by an electromagnet for generation of forces on superparamagnetic microspheres used in manipulation of single molecules or cells. Single molecule force spectroscopy based on magnetic tweezers can be used in applications that require parallel readout of biopolymer stretching or biomolecular binding. The magnetic tweezers exert forces on the surface-immobilized macromolecule by pulling a magnetic bead attached to the free end of the molecule in the direction of the field gradient. In a typical force spectroscopy experiment, the pulling forces can range between subpiconewton to tens of piconewtons. In order to effectively provide such forces, an understanding of the source of the magnetic field is required as the first step in the design of force spectroscopy systems. In this study, we use a numerical technique, the method of auxiliary sources, to investigate the influence of electromagnet geometry and material parameters of the magnetic core on the magnetic forces pulling the target beads in the area of interest. The close proximity of the area of interest to the magnet body results in deviations from intuitive relations between magnet size and pulling force, as well as in the force decay with distance. We discuss the benefits and drawbacks of various geometric modifications affecting the magnitude and spatial distribution of forces achievable with an electromagnet.

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“…On the other hand, longer tensioned microfibers can be supplied for coiling. However, because of the side leakage of magnetic flux in the entire iron core of the EMN [21], it is an arduous task to precisely control the magnetic microfibers at the tip of the EMN, but the tip control of the EMN is key to precisely positioning the microfiber all over the micropillar as desired.…”

Section: Introductionmentioning

confidence: 99%

Assembly of alginate microfibers to form a helical structure using micromanipulation with a magnetic field

Sun

Huang

Shi

et al. 2016

J. Micromech. Microeng.

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Helical structures assembled using alginate microfibers have a promising spatial architecture mimicking in vivo vessels for culturing vascular cells. However, the helical structure can only be assembled at the macroscale, since a microassembly-based approach has not yet been developed. In this paper, we propose a magnetic-field-based micromanipulation method to fabricate a helical microstructure. By microfluidic spinning, alginate microfibers encapsulating magnetic nanoparticles are synthesized to enable the control of an electromagnetic needle (EMN). We developed a microrobotic system to actuate a micropipette to fix a free end of the microfiber, and then move the EMN to reel the microfiber around a micropillar. The motion of the EMN is guided using an upright microscope and a side-view camera. Because of the limitation of operation space, a spacer sleeve was designed to keep the tip of the EMN attracted to the microfiber, and simultaneously to keep the other part of the EMN isolated from the microfiber. To ensure the availability of the microfiber for continuously coiling, we enable the EMN tip to slide on the surface of the microfiber without changing the tensioning of the microfiber for positioning control. Furthermore, stable and repeatable micromanipulation was achieved to form multi-turn microfiber coils based on the motion planning of the EMN. Finally, we successfully fabricated a helical microstructure that can be applied in vascular tissue engineering in the future.

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Optimization of force produced by electromagnet needles acting on superparamagnetic microparticles

Cited by 11 publications

References 29 publications

Tweezing of Magnetic and Non‐Magnetic Objects with Magnetic Fields

Tweezing of Magnetic and Non‐Magnetic Objects with Magnetic Fields

Quantitative modeling of forces in electromagnetic tweezers

Assembly of alginate microfibers to form a helical structure using micromanipulation with a magnetic field

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