Dynamic Assembly of Small Parts in Vortex–Vortex Traps Established within a Rotating Fluid

• Published in: Advanced materials (Weinheim) 2019-08, Vol.31 (32), p.e1902298-n/a
• Main Authors: Lee, Taehoon, Sobolev, Yaroslav I., Cybulski, Olgierd, Grzybowski, Bartosz A.
• Format: Article
• Language: English
• Subjects: 3D confinement; Angular velocity; Assembling; Circular orbits; dynamic self‐assembly; Fluid dynamics; Hopf bifurcation; particle trapping; Rotating fluids; Rotation; Trapping; vortex flows; Vortices
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.201902298

Stable, purely fluidic particle traps established by vortex flows induced within a rotating fluid are described. The traps can manipulate various types of small parts, dynamically assembling them into high‐symmetry clusters, cages, interlocked architectures, jammed colloidal monoliths, or colloidal formations on gas bubbles. The strength and the shape of the trapping region can be controlled by the strengths of one or both vortices and/or by the system's global angular velocity. The system exhibits a range of interesting dynamical behaviors including a Hopf‐bifurcation transition between equilibrium‐point trapping and the so‐called limit cycle in which the particles are confined to circular orbits. Theoretical considerations indicate that these vortex–vortex traps can be further miniaturized to manipulate objects with sizes down to ≈10 µm. Coaxial vortices created within a rotating fluid establish a region in which small particles, lighter than the fluid, can be trapped and dynamically assembled into various clusters, cages, interlocked architectures, or jammed colloidal monoliths. The trapping is due to an interplay between centripetal forces acting in the radial direction and vortex‐imparted forces acting along the system's axis of rotation.