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Maneuvering Micro Robot for Swimming in the MRI Bore

Proceedings article published in 2012 by N. Krakover, G. Kósa
This paper is available in a repository.
This paper is available in a repository.

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Preprint: policy unknown
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Postprint: policy unknown
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Abstract

Magnetic micro robots are usually implement a permanent magnet to swim in the body [1]. Our swimming method differs from those micro robots because we utilize non ferromagnetic coils in order disturb minimally the image of the MRI. Instead of alternating the external magnetic field in order to achieve movement, we introduce sinusoidal signals (same frequency, different amplitude, phase and DC offset) into the coils that create an undulating motion to swim. This study reports on the experiments to test our swimming concept. The abilities of these swimmers were examined by us in the past [2] The swimmer is made from two 5X5 mm coils from 50 turns of Ø0.05 mm copper wire. Experiments that require more power, like swimming in liquid viscous, used a greater number of turns (up to 200). The coils are situated in elastic polymer such as scotch tape. The entire swimmer size is 2-6 cm 2 . The power source of the swimmer is external and is also used to hang the swimmer. In order to generate an effect of swimming, there is a need for making constant magnetic field. For this purpose an electromagnet is used wrapped around an iron core, with a gap, thus the magnetic field in the gap is approximately parallel. Direct current of 6 amp creates a magnetic field of 0.1 Tesla at the center with the size of 10X10X10 cm 3 (See Fig 1a). (a) (b) Figure 1: (a) Experimental System and (b) swimming along the constant magnetic field B 0 First we tested the swimmer's ability to move to the direction of the B 0 field. Frequency scan revealed that the swimmer's natural frequency is at the maximum 32-34 Hz (highest swimming speed). The maximal swimming velocity at the resonance was about 12 cm per second. Fig 1b shows the change in swimming velocity as a function of frequency. Coils for MRI emulator Micro Swimmer DC supply Signal Generator I Signal Generator II Water Vessel C arm B 0