Diffusion of colloids in one-dimensional light channels

Single-file diffusion (SFD), prevalent in many chemical and biological processes, refers to the one-dimensional motion of interacting particles in pores which are so narrow that the mutual passage of particles is excluded. Since the sequence of particles in such a situation remains unaffected over time t , this leads to strong deviations from normal diffusion, e.g. an increase of the particle mean-square-displacement as the square root of t . We present experimental results of the diffusive behaviour of colloidal particles in one-dimensional channels with varying particle density. The channels are realized by means of a scanning optical tweezers. Based on a new analytical approach (Kollmann 2003 Phys. Rev. Lett. 90 180602) for SFD, we can predict quantitatively the long-time, diffusive behaviour from the short time density fluctuations in our systems.