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Related Concept Videos

Magnetic Field due to Moving Charges01:23

Magnetic Field due to Moving Charges

A stationary charge creates and interacts with the electric field, while a moving charge creates a magnetic field.
Consider a point charge moving with a constant velocity. Like the electric field, the magnetic field at any point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the source point and the field point. However, unlike the electric field, the magnetic field is always perpendicular to the plane containing the line...
Energy In A Magnetic Field01:24

Energy In A Magnetic Field

If a magnetic field is sustained, there must be a current in a closed circuit or loop, implying some energy has been spent in creating the field. If this energy is not dissipated via the circuit's resistance, it is stored in the field.
Take an ideal inductor with zero resistance. Although it's practically impossible, assume that the coil's resistance is so small that it is practically negligible. The loss of the field's energy to dissipate thermal energy (or heat) is thus negligible.
The energy...
Torque On A Current Loop In A Magnetic Field01:13

Torque On A Current Loop In A Magnetic Field

The most common application of magnetic force on current-carrying wires is in electric motors. These consist of loops of wire, which are placed between the magnets with a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate, thus converting electrical energy to mechanical energy.
Consider a rectangular current-carrying loop containing N turns of wire, placed in a uniform magnetic field. The net force on a current-carrying loop...
Diamagnetic Shielding of Nuclei: Local Diamagnetic Current01:14

Diamagnetic Shielding of Nuclei: Local Diamagnetic Current

An applied magnetic field causes the electrons present in the molecule to circulate, setting up a local diamagnetic current within the molecule. The local diamagnetic current arising from circulating sigma-bonding electrons induces a magnetic field, Blocal that opposes the applied magnetic field, B0. The effective magnetic field experienced by these nuclei is given by the difference between the applied and local magnetic fields in a phenomenon called local diamagnetic shielding. Essentially,...
Magnetism01:30

Magnetism

Magnets are commonly found in everyday objects, such as toys, hangers, elevators, doorbells, and computer devices. Experimentation on these magnets shows that all magnets have two poles: one is labeled north (N) and the other south (S). Magnetic poles repel if they are alike and attract if unlike. Moreover, both poles of a magnet attract unmagnetized pieces of iron.
An individual magnetic pole cannot be isolated. No matter how small, every piece of a magnet contains a north pole and a south...
Force On A Current Loop In A Magnetic Field01:17

Force On A Current Loop In A Magnetic Field

Magnetic forces on wires carrying current are most frequently applied in motors. A DC motor is a device that converts electrical energy into mechanical work. In motors, wire loops are enclosed in a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate. The direction of the current is reversed once the loop's surface area is lined up with the magnetic field, causing a constant torque on the loop. During the process, commutators...

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Related Experiment Video

Updated: Jun 5, 2026

Computer Numerical Control Micromilling of a Microfluidic Acrylic Device with a Staggered Restriction for Magnetic Nanoparticle-Based Immunoassays
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Computer Numerical Control Micromilling of a Microfluidic Acrylic Device with a Staggered Restriction for Magnetic Nanoparticle-Based Immunoassays

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Magnetic core shell nanoparticles trapping in a microdevice generating high magnetic gradient.

Bruno Teste1, Florent Malloggi, Anne-Laure Gassner

  • 1Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques (PECSA), UMR 7195 CNRS-ESPCI-ENSCP, France.

Lab on a Chip
|January 22, 2011
PubMed
Summary

A novel microchip effectively traps tiny magnetic core shell nanoparticles (MCSNPs) using iron beads. This breakthrough enables efficient nanoparticle concentration and release in microfluidic systems.

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Fabrication of Magnetic Platforms for Micron-Scale Organization of Interconnected Neurons
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Fabrication of Magnetic Platforms for Micron-Scale Organization of Interconnected Neurons

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Last Updated: Jun 5, 2026

Computer Numerical Control Micromilling of a Microfluidic Acrylic Device with a Staggered Restriction for Magnetic Nanoparticle-Based Immunoassays
09:58

Computer Numerical Control Micromilling of a Microfluidic Acrylic Device with a Staggered Restriction for Magnetic Nanoparticle-Based Immunoassays

Published on: June 23, 2022

Fabrication of Magnetic Platforms for Micron-Scale Organization of Interconnected Neurons
09:54

Fabrication of Magnetic Platforms for Micron-Scale Organization of Interconnected Neurons

Published on: July 14, 2021

Area of Science:

  • Microfluidics
  • Nanotechnology
  • Biomedical Engineering

Background:

  • Traditional magnetic trapping methods struggle with small nanoparticles (30 nm) in microfluidic systems.
  • External magnets alone lack sufficient field gradients to capture these minute magnetic core shell nanoparticles (MCSNPs).

Purpose of the Study:

  • To develop a simple yet efficient microchip for trapping and releasing MCSNPs within microfluidic channels.
  • To enhance magnetic field gradients locally for improved nanoparticle capture.

Main Methods:

  • A microchip design incorporating a packed bed of micrometric iron beads (6-8 μm) against a microchannel restriction.
  • Utilizing high magnetic permeability iron beads to concentrate magnetic field lines from an external permanent magnet.
  • Characterization through numerical simulations (magnetic flux density, force mapping) and fluorescent imaging of MCSNPs.

Main Results:

  • Numerical simulations revealed MCSNPs preferentially trap at iron bead magnetic poles, with forces amplified by three orders of magnitude.
  • Experimental trapping efficiency was validated using fluorescent MCSNPs across various flow rates and magnet positions.
  • Achieved efficient trapping and release within 20 seconds at 100 μL/h flow rate.

Conclusions:

  • The developed microchip design significantly enhances magnetic trapping of small nanoparticles in microfluidics.
  • The iron bead-based system provides a preconcentration factor of 4000, demonstrating high efficiency.
  • This method offers a practical solution for manipulating and concentrating MCSNPs for various applications.