Cooperative Behavior and Pattern Formation in Mixtures of Driven and   Nondriven Colloidal Assemblies
  We simulate a disordered assembly of particles interacting through a repulsive Yukawa potential with a small fraction of the particles coupled to an external drive. Distortions in the arrangement of the nondriven particles produce a dynamically induced effective attraction between the driven particles, giving rise to intermittent one-dimensional stringlike structures. The velocity of a moving string increases with the number of driven particles in the string. We identify the average stable string length as a function of driving force, background particle density, and particle charge. This model represents a new type of collective transport system composed of interacting particles moving through deformable disorder. 
C. Reichhardt and C.J. Olson Reichhardt