Self-assembly of magnetically interacting cubes by a turbulent fluid flow

Abstract

Previous work (e.g. [1], [2]) has demonstrated that combining mechanical vibration with magnetic interactions can result in the self assembly of complex structures, albeit at low yield. Here we introduce a system where the yield of self assembled structures is quantitatively predicted by a theoretical analysis. Millimeter sized magnetic blocks, designed to form chains as their minimal energy state, are placed in a turbulent fluid flow. The distribution of chain lengths that form is quantitatively consistent with predictions, showing that the chain length distribution coincides with that of monomers/polymers in a thermal bath, with the turbulence strength parameterizing the effective temperature.

Communication: Effective temperature and glassy dynamics of active matter

“…Other forms of active matter range from assemblies of entire microorganisms 1 to collections of artificial microscopic swimmers which are self-propelled 2,3 and turbulently agitated active suspensions on the colloidal scale. 4 In this Communication, we show that the steady-state statistical mechanics of these diverse out-of-equilibrium forms of active matter as well as their low-frequency fluctuations and responses can be described using the concept of an effective temperature. The notion of effective temperature has been useful in describing passive glassy systems, 5 weakly driven systems such as gently sheared supercooled liquids and glasses 6,7 and vibrated granular matter, 8 driven vortex matter, 9,10 as well as in approximate theories and simulations of active biological matter.…”

Magnetic interactions in 2D and 3D arrays

“…Exciting ideas exist to let particles assemble by themselves [Whitesides and Grzybowski, 2002]. Magnetic interaction are excellently suited to investigate self-assembly of large scale prototypes of micro systems [Ilievski et al, 2011a;Shetye et al, 2008].…”

Observing magnetic objects in fluids

“…Stambaugh et al (2003) reported self-assembled 2D structures of centimetre-sized spherical particles with internal magnets that were shaken vertically, and observed different resulting structures that were based on particle concentration and magnet shape. Ilievski et al (2011b) demonstrated self-assembly of centimetre-sized magnetic cubes into chains in a turbulent flow by submerging them in a rotating reactor filled with water, this way introducing eddy flows as a disturbing energy. They also introduced the concept of effective temperature, describing the motion of particles as if Brownian by nature.…”

“…Smart particles have been successfully self-assembled on macroscopic scale, forming electrically functional networks (C) (Gracias et al, 2000). Self-assembly dynamics may be simulated on macroscopic scale (D) (Ilievski et al, 2011b).involved. Analogue simulations in the form of a macroscopic self-assembly reactor can act as an alternative, greatly increasing visibility.…”

“…We chose the particle density to balance these forces, causing them to appear weightless. Following Ilievski et al (2011b), we use a turbulent water flow as an agitating source, simulating the Brownian motion on a microscopic scale. We employ permanent magnets, resulting in attraction forces between the particles.…”