title: Transitional behavior in hydrodynamically coupled oscillators.
abstract: In this article we consider the complete set of synchronized and phase-locked states available to pairs of hydrodynamically coupled colloidal rotors, consisting of spherical beads driven about circular paths in the same, and in opposing senses. Oscillators such as these have previously been used as coarse grained, minimal models of beating cilia. Two mechanisms are known to be important in establishing synchrony. The first involves perturbation of the driving force, and the second involves deformation of the rotor trajectory. We demonstrate that these mechanisms are of similar strength, in the regime of interest, and interact to determine observed behavior. Combining analysis and simulation with experiments performed using holographic optical tweezers, we show how varying the amplitude of the driving force perturbation leads to a transition from synchronized to phase-locked states. Analogies with biological systems are discussed, as are implications for the design of biomimetic devices.
authors.affiliation: H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, U.K.
authors.forename: S
authors.initials: S
authors.lastname: Box
authors.affiliation: H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, U.K.
authors.forename: L
authors.initials: L
authors.lastname: Debono
authors.affiliation: Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
authors.forename: D B
authors.initials: DB
authors.lastname: Phillips
authors.affiliation: ASCR, Institute of Scientific Instruments, Kràlovopolskà 147, 612 64 Brno, Czech Republic.
authors.forename: S H
authors.initials: SH
authors.lastname: Simpson