Single-file diffusion, prevalent in many chemical and biological processes, refers to the one-dimensional motion of interacting particles in pores which are that narrow that the mutual passage of particles is excluded. Since the sequence of particles in such a situation remains unaffected over time, this leads to strong deviations from normal diffusion. Besides theoretical interest in this non-Fickian diffusion regime, single-file diffusion might be also of relevance for efficient separation mechanisms in polydisperse particle mixtures or DNA fragments. Although during recent years single-file diffusion was discussed in numerous theoretical publications, experimental evidence for the occurence of this mechanism, as provided by molecular diffusion studies in nanoporous mordenite crystallites, is rare. In addition, results obtained from different groups on the same systems were contradictory, which has been attributed to deviations from an ideal channel structure in such materials. The current project suggests the use of colloidal particles as a promising, alternative experimental approach for systematic studies of single-file diffusion. Artificial channel structures are provided by strong light fields which serve as optical traps for colloidal particles. Due to the high flexibility of such optical tweezers, the channel geometry can be easily changed and the conditions under which single-file diffusion occurs, can be studied. Since experiments with colloidal particles can be carried out under well-defined conditions, this allows direct comparison with theoretical predictions.Single-file diffusion, prevalent in many chemical and biological processes, refers to the one-dimensional motion of interacting particles in pores which are that narrow that the mutual passage of particles is excluded. Since the sequence of particles in such a situation remains unaffected over time, this leads to strong deviations from normal diffusion. Besides theoretical interest in this non-Fickian diffusion regime, single-file diffusion might be also of relevance for efficient separation mechanisms in polydisperse particle mixtures or DNA fragments. Although during recent years single-file diffusion was discussed in numerous theoretical publications, experimental evidence for the occurence of this mechanism, as provided by molecular diffusion studies in nanoporous mordenite crystallites, is rare. In addition, results obtained from different groups on the same systems were contradictory, which has been attributed to deviations from an ideal channel structure in such materials. The current project suggests the use of colloidal particles as a promising, alternative experimental approach for systematic studies of single-file diffusion. Artificial channel structures are provided by strong light fields which serve as optical traps for colloidal particles. Due to the high flexibility of such optical tweezers, the channel geometry can be easily changed and the conditions under which single-file diffusion occurs, can be studied. Since experiments with colloidal particles can be carried out under well-defined conditions, this allows direct comparison with theoretical predictions.
