Description: Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

This title appears in the Scientific Report : 2015

Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependen...

Personal Name(s):	Chen, La
	Offenhäusser, Andreas / Krause, Hans-Joachim (Corresponding Author)
Contributing Institute:	JARA-FIT; JARA-FIT Bioelektronik; ICS-8 Bioelektronik; PGI-8
Published in:	Review of scientific instruments, 86 (2015) 4, S. 044701 -
Imprint:	[S.l.] American Institute of Physics 2015
DOI:	10.1063/1.4916255
PubMed ID:	25933874
Document Type:	Journal Article
Research Program:	Controlling Configuration-Based Phenomena Physical Basis of Diseases Engineering Cell Function
Link:	OpenAccess OpenAccess
	Publikationsportal JuSER

Please use the identifier: http://dx.doi.org/10.1063/1.4916255 in citations.
Please use the identifier: http://hdl.handle.net/2128/16752 in citations.

As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm2, a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle’s position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.