The synchronization of superparamagnetic beads driven by a micro-magnetic ratchet.

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We present theoretical, numerical, and experimental analyses on the non-linear dynamic behavior of superparamagnetic beads exposed to a periodic array of micro-magnets and an external rotating field. The agreement between theoretical and experimental results revealed that non-linear magnetic forcing dynamics are responsible for transitions between phase-locked orbits, sub-harmonic orbits, and closed orbits, representing different mobility regimes of colloidal beads. These results suggest that the non-linear behavior can be exploited to construct a novel colloidal separation device that can achieve effectively infinite separation resolution for different types of beads, by exploiting minor differences in their bead's properties. We also identify a unique set of initial conditions, which we denote the "devil's gate" which can be used to expeditiously identify the full range of mobility for a given bead type.





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Gao, Lu, Norman J Gottron, Lawrence N Virgin and Benjamin B Yellen (2010). The synchronization of superparamagnetic beads driven by a micro-magnetic ratchet. Lab Chip, 10(16). pp. 2108–2114. 10.1039/c003836a Retrieved from

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Lawrence N. Virgin

Professor in the Thomas Lord Department of Mechanical Engineering and Materials Science

Professor Virgin's research is centered on studying the behavior of nonlinear dynamical systems. This work may be broadly divided into two components. First, investigation of the fundamental nature of nonlinear systems based on a mathematical description of their underlying equations of motion. Both analytical and numerical techniques are used with special attention focused on the loss of stability of dynamical systems.

The second area of interest is to apply recent results from nonlinear dynamical systems theory to problems of practical engineering importance. These include the nonlinear rolling motion of ships leading to capsize; buckling of axially-loaded structural components; aeroelastic flutter of aircraft panels at high supersonic speeds; vibration isolation based on nonlinear springs; energy harvesting; damage detection and structural health monitoring; and the dynamics of very flexible structures including solar sails and marine risers. Professor Virgin conducts mechanical experiments to complement these studies.

More recently, he has developed an interest in 3D-printing, with applications in models for high-fidelity experiments, and for use in the teaching arena.

The flavor of much of this work is contained in the books:

Introduction to Experimental Nonlinear Dynamics, L.N. Virgin, Cambridge University Press, 2000.

Vibration of Axially Loaded Structures, L.N. Virgin, Cambridge University Press, 2007.

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