Motion of Magnetic Chains in a Vibrating Field

Y-H Li, S-T Sheu, J-M Pai, C-Y Chen
National Chiao Tung University, TW

Keywords: magnetic particles, micro chains, vibrating field

Summary:

In this work, we have carried out an intensive experimental study on the manipulations of micro magnetic particle chains under vibrating magnetic fields. The chain is firstly formed by a uniform directional field, and then manipulated by an additional vibrating field. The present methodology represents a simple reversible chaining process, whose particles can be re-dispersed after removal of the field. This particular configuration possesses potential applications in MEMS systems, including micro mixers, actuators and swimmers. By investigating the phase lag between the external field and chain, we are able to evaluate the effects of control parameters, such as the perpendicular field strength, directional field strength and length of chain. We demonstrate the chains appear different behaviors, from rigid body vibrations, bending distortions to breaking failures, under different conditions. In addition, an interesting reverse vibration is induced if the phase lag is greater than 90 degrees. It is known that dynamics of micro-chains are dominated by the dimensionless Mason number (Mn), which determines the ratio between magnetic forces and hydrodynamic drags. Based on the experimental results, a critical global Mason number, i.e. Mn>0.02, is proposed that is able to predict the behaviors of chain ruptures.