Entropic release of a big sphere from a cylindrical vessel

Insertion and release of a solute into and from a cylindrical vessel comprising biopolymers is a fundamental function in biological systems. In earlier works, we reported that the solvent-entropy (SE) effect plays imperative roles for insertion. Here we show that release is also achievable by the SE effect: the solute can be moved from an entrance at one end of the vessel to an exit at the other end using a continuous variation of the vessel geometry. Since the SE effect is rather insensitive to the solute–solvent affinity, our result may provide a clue to the ‘multidrug efflux’ of TolC.