  The single-particle and collective dynamics of systems comprising Janus
motors, solvent and reactive solute species maintained in nonequilibrium states
are investigated. Reversible catalytic reactions with the solute species take
place on the catalytic faces of the motors, and the nonequilibrium states are
established by imposing either constant-concentration reservoirs that feed and
remove reactive species, or through out-of-equilibrium fluid phase reactions.
We consider general intermolecular interactions between the Janus motor
hemispheres and the reactive species. For single motors, we show that the
reaction rate depends nonlinearly on an applied external force when the system
is displaced far from equilibrium. We also show that a finite-time fluctuation
formula derived for fixed catalytic particles describes the nonequilibrium
reactive fluctuations of moving Janus motors. Simulation of the collective
dynamics of small ensembles of Janus motors with reversible kinetics under
nonequilibrium conditions are carried out and the spatial and orientational
correlations of dynamic cluster states are discussed. The conditions leading to
the instability of the homogeneous motor distribution and the onset of
nonequilibrium dynamical clustering are described.
