Single-file diffusion (SFD) refers to the one-dimensional motion of particles in pores which are that narrow that mutual passage of particles is excluded. Since the sequence of particles remains the same, this leads to strong deviations from normal diffusion, e.g. an increase of the particle mean-square-displacement as t1/2. Besides theoretical interest, SFD is also relevant for efficient separation mechanisms of polydisperse particle mixtures or DNA fragments. Although during recent years SFD has been discussed in numerous theoretical publications, experimental evidence for the occurrence of this mechanism as provided by molecular diffusion studies in nanoporous mordenite crystallites remains still contradictory. In our experiments we use colloidal particles as a promising alternative experimental approach for systematic studies of SFD. Channels can be created by topographical structures or by strong light fields which serve as traps for the particles and allow to study the experimentall conditions under which SFD can be observed.
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