Depending on the implementation, magnetic tweezers can be divided into several categories including translational or rotational, unipolar or multipolar.
The most simple setup is the unipolar translational magnetic tweezer. It consists of an electromagnet with a paramagnetic core material and a tip-shaped end. This results in a high field gradient around the tip. Any paramagnetic material within that gradient is magnetized and pulled towards the tip. The force magnitude depends on the magnitude and gradient of the magnetic field. While the magnitude can be controlled by the current that drives the electromagnet, the gradient depends on the distance to the tip of the core. Alternatively, the electromagnet can be replaced by a permanent magnetic needle.
Several electromagnets can be combined into a multipolar magnetic tweezer setup, allowing for three-dimensional translation, rotation and trapping of magnetic particles.
When permanently magnetized particles are subjected to a magnetic field, their internal magnetic moment will try to align with the external field, resulting in a rotational or twisting force. Magnetic twisting has been used to study the viscoelastic properties of living cells and biological materials.
While early experiments used magnetic powder as probes and measured the resulting change of the magnetic field, nowadays magnetic microbeads of varying sizes and well-known magnetic properties are commercially available, and microscope image processing can be used to detect the displacement of the probes.
Ingber Lab (Harvard Medical School)
Saleh Lab (Material science department UC Santa Barbara)
Mechanobiology Group (MIT, Roger Kamm)
Nanosystems Measurement & Controls Lab (Department of Mechanical Engineering & Material Science, University of Pittsburgh)
So Lab (MIT)
Forgacs Lab (Department of Physics & Astronomy, University of Missouri)
Wirtz Lab (Johns Hopkins University)
Bustamante Lab (University of California, Berkeley)
Marko Lab (Northwestern University)
Forde Lab (Simon Fraser University, British Columbia)
Kazuhiko Kinosita (Waseda University, Tokyo)
Molecular and Nanoscale Physics Group (University of Leeds, Leeds, England)
Erich Sackmann (Technical University of Munich, Germany)
Biophysical Engineering Group (University of Twente, The Netherlands)
Fabry Lab (University of Erlangen-Nuremberg, Germany)
Ralf Seidel - DNA Motors (BIOTEC, TU Dresden, Germany)
Joachim Spatz (University of Heidelberg, Germany)
Cécile Sykes (Curie Institute, Paris, France)
David Bensimon and Vincent Croquette (École Normale Supérieure, Paris, France)
Effects of magnetic needle acupuncture on blood pressure and plasma ET-1 level in the patient of hypertension.(Abstracts: The Journal of Traditional Chimese Medicine Abstracts December 2003)(Brief article)
Jun 01, 2004; Endothelin-1 (ET-1) is a bio-peptide with a strong vasoconstrictive action which plays an important role in the regulation of...