2026-09-19T19:46:58Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/837802022-01-13T07:54:07Zcom_1721.1_7582com_1721.1_7581col_1721.1_131024
Alfredo Alexander-Katz and Mehran Kardar.
Su, Yi-Han, S.B. Massachusetts Institute of Technology
Massachusetts Institute of Technology. Department of Physics.
Massachusetts Institute of Technology. Department of Physics
2014-01-09T19:54:13Z
2014-01-09T19:54:13Z
2013
http://hdl.handle.net/1721.1/83780
864909439
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 24).
In this research, the manipulation of colloidal systems composed of superparamagnetic particles in water is studied by a simulation method. In response to an external magnetic field, the dipoles drive the beads to self-assemble into chains, which rotate and consequently move across a nearby surface. Under strong surface-interaction, the dynamic and equilibrium structures are modeled using a Bell model and measured using Monte Carlo-type update steps. It is shown that the walking motion can be characterized as two different regimes corresponding to an increase of the rotating arm from half to all of the chain-length as the activation barrier of binding interaction increases with a constant overall increase in energy. When operating at rotational frequencies from 1 Hz to 9 Hz and applied field from I mT to 9 mT, the corresponding translational velocities of chain-like rotors can be approximated with a two-state model until the fragmentation transition of chain-like rotors takes place. The translational velocities of chain-like rotors scale linearly with respect to number of beads.
by Yi-Han Su.
S.B.
24 pages
eng
Massachusetts Institute of Technology
M.I.T. theses are protected by
copyright. They may be viewed from this source for any purpose, but
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http://dspace.mit.edu/handle/1721.1/7582
Physics.
Motion-reversal in colloidal walkers
Thesis
application/pdf
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Publication
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<Abstract>In this research, the manipulation of colloidal systems composed of superparamagnetic particles in water is studied by a simulation method. In response to an external magnetic field, the dipoles drive the beads to self-assemble into chains, which rotate and consequently move across a nearby surface. Under strong surface-interaction, the dynamic and equilibrium structures are modeled using a Bell model and measured using Monte Carlo-type update steps. It is shown that the walking motion can be characterized as two different regimes corresponding to an increase of the rotating arm from half to all of the chain-length as the activation barrier of binding interaction increases with a constant overall increase in energy. When operating at rotational frequencies from 1 Hz to 9 Hz and applied field from I mT to 9 mT, the corresponding translational velocities of chain-like rotors can be approximated with a two-state model until the fragmentation transition of chain-like rotors takes place. The translational velocities of chain-like rotors scale linearly with respect to number of beads.</Abstract>
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