title: Single-File Escape of Colloidal Particles from Microfluidic Channels.
abstract: Single-file diffusion is a ubiquitous physical process exploited by living and synthetic systems to exchange molecules with their environment. It is paramount to quantify the escape time needed for single files of particles to exit from constraining synthetic channels and biological pores. This quantity depends on complex cooperative effects, whose predominance can only be established through a strict comparison between theory and experiments. By using colloidal particles, optical manipulation, microfluidics, digital microscopy, and theoretical analysis we uncover the self-similar character of the escape process and provide closed-formula evaluations of the escape time. We find that the escape time scales inversely with the diffusion coefficient of the last particle to leave the channel. Importantly, we find that at the investigated microscale, bias forces as tiny as 10^{-15}  N determine the magnitude of the escape time by drastically reducing interparticle collisions. Our findings provide crucial guidelines to optimize the design of micro- and nanodevices for a variety of applications including drug delivery, particle filtering, and transport in geometrical constrictions.
authors.affiliation: Dipartimento di Fisica e Astronomia "G. Galilei" (DFA) and Sezione CNISM, Università di Padova, Via Marzolo 8, 35131 Padova, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Locatelli
authors.affiliation: Dipartimento di Fisica e Astronomia "G. Galilei" (DFA) and Sezione CNISM, Università di Padova, Via Marzolo 8, 35131 Padova, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Pierno
authors.affiliation: Dipartimento di Fisica e Astronomia "G. Galilei" (DFA), Sezione INFN and Sezione CNISM, Università di Padova, Via Marzolo 8, 35131 Padova, Italy.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Baldovin
authors.affiliation: Dipartimento di Fisica e Astronomia "G. Galilei" (DFA), Sezione INFN and Sezione CNISM, Università di Padova, Via Marzolo 8, 35131 Padova, Italy.
authors.forename: Enzo
authors.initials: E
authors.lastname: Orlandini
authors.affiliation: Cavendish Laboratory, Cambridge CB30HE, United Kingdom.
authors.forename: Yizhou
authors.initials: Y
authors.lastname: Tan
authors.affiliation: Cavendish Laboratory, Cambridge CB30HE, United Kingdom.
authors.forename: Stefano
authors.initials: S
authors.lastname: Pagliara