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- Title
Magnet polepiece design for uniform magnetic force on superparamagnetic beads.
- Authors
Fallesen, Todd; Hill, David B; Steen, Matthew; Macosko, Jed C; Bonin, Keith; Holzwarth, George
- Abstract
Here we report construction of a simple electromagnet with novel polepieces which apply a spatially uniform force to superparamagnetic beads in an optical microscope. The wedge-shaped gap was designed to keep partial differential B(x)/ partial differential y constant and B large enough to saturate the bead. We achieved fields of 300-600 mT and constant gradients of 67 T/m over a sample space of 0.5x4 mm(2) in the focal plane of the microscope and 0.05 mm along the microscope optic axis. Within this space the maximum force on a 2.8 microm diameter Dynabead was 12 pN with a spatial variation of approximately 10%. Use of the magnet in a biophysical experiment is illustrated by showing that gliding microtubules propelled by the molecular motor kinesin can be stopped by the force of an attached magnetic bead.
- Publication
The Review of scientific instruments, 2010, Vol 81, Issue 7, p074303
- ISSN
1089-7623
- Publication type
Journal Article
- DOI
10.1063/1.3469792