Microscale Motion Control through Ferromagnetic Films

Abstract

Actuation and control of motion in micromechanical systems are technological challenges, since they are accompanied by friction and wear, principal and well-known sources of lifetime reduction. In this theoretical work we propose a non-contact motion control technique based on the introduction of a magnetic interaction, i.e., non-contact magnetic friction. The latter is realized by coating two non-touching sliding bodies with ferromagnetic films. The resulting dynamics is determined by shape, size and ordering of magnetic domains arising in the films below the Curie temperature. We demonstrate that the domain behavior can be tailored by acting on handles like ferromagnetic coating preparation, external magnetic fields and the finite distance between the plates. In this way, motion control can be achieved without mechanical contact. Moreover, we discuss how such handles can disclose a variety of sliding regimes. Finally, we propose how to practically implement the proposed model sliding system.

Moving magnets in a micromagnetic finite-difference framework

“…Section III elaborates on the technical details of the movement and eddy current implementations. In Section IV, we test our implementation with example simulations, comparing the obtained results to those of previous works on magnetic friction [9] and eddy currents [16,17]. Finally, in Section V we summarize the main points of the article and conclude with thoughts on possible future work.…”

“…The films were initialized to a stripe pattern similar to Ref. [9], with approximately 80 nm wide stripes and let relax (Resulting in a system similar to what was shown in Fig. 1), after which the upper film was driven in the +x-direction by a spring moving at a constant velocity v d = 2 m/s for 300 ns.…”

“…To see whether the film distance would affect the friction behavior in our tests as it did in Ref. [9], we ran simulations for various film distances, ranging from 20 nm to 80 nm. We started the simulation with the spring already ahead of the slider by 80 nm so that the beginning part of the simulation, where the spring slowly elongates increasing the force, is shorter.…”

“…An area currently lacking in micromagnetics is the capability of simulating mechanical motion of magnets and the interplay of motion and the domain dynamics of magnets moving relative to each other. The relative motion of small-scale magnets is relevant in studying phenomena such as magnetic friction [7][8][9][10][11], and for applications such as magnetic force microscopy [12], and micro-and nanomanipulation [13,14]. Despite the scientific interest in these areas, simulation frameworks capable of general micromagnetic simulations coupled with the motion dynamics of the magnets, to the authors' knowledge, do not exist.…”

Does rotational melting make molecular crystal surfaces more slippery?

“…The application of external fields (electric, magnetic, etc.) to the sliding contact was also exploited to tune effectively the frictional response in different kind of tribological systems [5][6][7][8] . Another, subtler route worth exploring is the possible change of adhesion and friction experienced by a nanoslider when a collective property of the substrate, for example some pre-existing ordering is altered under the action of an external field, or of temperature.…”