Karine Guevorkian

Valles Lab

Biological Physics
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We investigate the swimming response of microorganisms to intense magnetic fields and magnetic forces. We have developed a method based on magneto-Archimedes principle that employs magnetic forces to simulate variable gravity environments for the study of gravi-sensitivity of cells. Paramecium picture The May 2006 issue of Scientific American has a short paragraph about our research (PDF).

My experiments are performed on single cell protozoan Paramecium caudatum. A rather large (200 micrometer long) and commonly used ciliate, which possesses gravi-sensing abilities. We carried out most of our experiments at the National High Magnetic Field Laboratory.


All our experiments are performed in solenoid magnet systems that produce non-homogenous magnetic fields. The field is at its maximum at the center of the magnet whereas the magnetic force, since it is proportional to the field-field gradient, has two maxima off the center as shown with the blue curve. When a diamagnetic object is placed in non-homogenous magnetic field, the induced magnetic moments are such that the object is repelled from the maximum field region (away from the center). Therefor the objects placed above the center of the magnet feel a decreased gravitation pull and vice versa. The total force profile is shown in red, the arrows show the relative magnitude of the force. Since biological matters are very weakly diamagnetic, we need strong forces of order of few thousand T2m-1 to manipulate them.

Schematic image of Diamagnetic Levitation

On the lefthand side of the above figure, (a), a schematic of a levitated object (movie) is illustrated. The righthand side, (b), shows the magnetic force (blue) and the total force (red) after taking into consideration the effect of gravity. The arrows show the direction and the magnitude of the total force.