title: Swimming in a crystal.
abstract: We study catalytic Janus particles and Escherichia coli bacteria swimming in a two-dimensional colloidal crystal. The Janus particles orbit individual colloids and hop between colloids stochastically, with a hopping rate that varies inversely with fuel (hydrogen peroxide) concentration. At high fuel concentration, these orbits are stable for 100s of revolutions, and the orbital speed oscillates periodically as a result of hydrodynamic, and possibly also phoretic, interactions between the swimmer and the six neighbouring colloids. Motile E. coli bacteria behave very differently in the same colloidal crystal: their circular orbits on plain glass are rectified into long, straight runs, because the bacteria are unable to turn corners inside the crystal.
authors.affiliation: SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK. abrown20@staffmail.ed.ac.uk.
authors.forename: Aidan T
authors.initials: AT
authors.lastname: Brown
authors.affiliation: SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK. abrown20@staffmail.ed.ac.uk.
authors.forename: Ioana D
authors.initials: ID
authors.lastname: Vladescu
authors.affiliation: SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK. abrown20@staffmail.ed.ac.uk.
authors.forename: Angela
authors.initials: A
authors.lastname: Dawson
authors.affiliation: SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK. abrown20@staffmail.ed.ac.uk.
authors.forename: Teun
authors.initials: T
authors.lastname: Vissers
authors.affiliation: SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK. abrown20@staffmail.ed.ac.uk.
authors.forename: Jana
authors.initials: J
authors.lastname: Schwarz-Linek
authors.affiliation: SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK. abrown20@staffmail.ed.ac.uk and Laboratoire de Physique des Solides, Université Paris-Sud, UMR 8502-91405 Orsay, France.
authors.forename: Juho S
authors.initials: JS
authors.lastname: Lintuvuori
authors.affiliation: SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK. abrown20@staffmail.ed.ac.uk.
authors.forename: Wilson C K
authors.initials: WC
authors.lastname: Poon