Related Experiment Video
Updated: Apr 10, 2026
08:50
High-Speed Magnetic Tweezers for Nanomechanical Measurements on Force-Sensitive Elements
Published on: May 12, 2023
3.0K
Biological magnetometry: torque on superparamagnetic beads in magnetic fields.
Maarten M van Oene1, Laura E Dickinson1, Francesco Pedaci1,2
1Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands.
Physical Review Letters
|June 13, 2015
Summary
Superparamagnetic beads
Area of Science:
- Biophysics
- Biochemistry
- Nanotechnology
Background:
- Superparamagnetic beads are essential tools in biophysics and biochemistry.
- The source of anisotropy enabling torque application in these beads is debated.
Purpose of the Study:
- To quantitatively investigate torques on superparamagnetic particles.
- To elucidate the origin of anisotropy in superparamagnetic beads.
Main Methods:
- Utilizing a biological motor to rotate superparamagnetic beads within a magnetic field.
- Tethering a bead to a single DNA molecule to measure angular trap stiffness.
Main Results:
- Demonstrated a π-periodic potential for rotating beads.
- Observed a nonlinear increase in angular trap stiffness with magnetic field strength.
- Identified nonuniform intrabead distribution of nanoparticles as the anisotropy source.
Conclusions:
- The study clarifies the anisotropy mechanism in superparamagnetic beads.
- Findings provide a deeper understanding for applications in biophysics and nanotechnology.
Related Concept Videos
01:13Torque On A Current Loop In A Magnetic Field
6.6K
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...
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...
6.6K
01:30Paramagnetism
3.3K
Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
3.3K
01:31Ferromagnetism
3.6K
Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
3.6K
01:27Magnetic Fields
8.0K
A moving charge or a current creates a magnetic field in the surrounding space, in addition to its electric field. The magnetic field exerts a force on any other moving charge or current that is present in the field. Like an electric field, the magnetic field is also a vector field. At any position, the direction of the magnetic field is defined as the direction in which the north pole of a compass needle points.
A magnetic field is defined by the force that a charged particle experiences...
A magnetic field is defined by the force that a charged particle experiences...
8.0K
01:17Force On A Current Loop In A Magnetic Field
4.7K
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...
4.7K
01:23Atomic Nuclei: Nuclear Relaxation Processes
1.4K
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
1.4K