title: Shedding light on the mechanism of asymmetric track etching: an interplay between latent track structure, etchant diffusion and osmotic flow.
abstract: The method of producing single track-etched conical nanopores has received considerable attention and found many applications in diverse fields such as biosensing, nanofluidics, information processing and others. The performance of an asymmetric nanopore is largely determined by its geometry, especially by the size and shape of its tip. In this paper we reconstruct the profiles of so-called conical pores fabricated by asymmetric chemical etching of ion tracks in polymer foil. Conductometric measurements during etching and field emission scanning electron microscopy examinations of the resulting pores were employed in order to determine the pore geometry. We demonstrate that the pore constriction geometry evolves through a variety of configurations with advancing time after breakthrough. While immediately after breakthrough the pore tips are trumpet-shaped, further etching is strongly affected by osmotic effects which eventually lead to bullet-shaped pore tips. We evidence that the osmotic flow appearing during asymmetric track etching has a determinative effect on pore formation. A convection-diffusion model is presented that semi-quantitatively explains the effect of osmotic processes under asymmetric track etching conditions. In addition, a phenomenon of reagent contaminant precipitation in nanopores is reported and discussed.
authors.affiliation: Joint Institute for Nuclear Research, Joliot-Curie Street 6, 141980 Dubna, Russian Federation. apel@jinr.ru and Dubna State University, Universitetskaya Street 19, 141980 Dubna, Russian Federation.
authors.forename: Pavel Y
authors.identifier: http://orcid.org/0000-0003-1259-163X
authors.initials: PY
authors.lastname: Apel
authors.affiliation: Joint Institute for Nuclear Research, Joliot-Curie Street 6, 141980 Dubna, Russian Federation. apel@jinr.ru.
authors.forename: Valery V
authors.initials: VV
authors.lastname: Bashevoy
authors.affiliation: Joint Institute for Nuclear Research, Joliot-Curie Street 6, 141980 Dubna, Russian Federation. apel@jinr.ru.
authors.forename: Irina V
authors.initials: IV
authors.lastname: Blonskaya
authors.affiliation: Joint Institute for Nuclear Research, Joliot-Curie Street 6, 141980 Dubna, Russian Federation. apel@jinr.ru.
authors.forename: Nikolay E
authors.initials: NE
authors.lastname: Lizunov
authors.affiliation: Joint Institute for Nuclear Research, Joliot-Curie Street 6, 141980 Dubna, Russian Federation. apel@jinr.ru.
authors.forename: Oleg L
authors.initials: OL
authors.lastname: Orelovitch
authors.affiliation: GSI Helmholtzzentrum für Schwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany and Materialwissenschaft, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Trautmann