title: Characterizing concentrated, multiply scattering, and actively driven fluorescent systems with confocal differential dynamic microscopy.
abstract: We introduce confocal differential dynamic microscopy (ConDDM), a new technique yielding information comparable to that given by light scattering but in dense, opaque, fluorescent samples of micron-sized objects that cannot be probed easily with other existing techniques. We measure the correct wave vector q-dependent structure and hydrodynamic factors of concentrated hard-sphere-like colloids. We characterize concentrated swimming bacteria, observing ballistic motion in the bulk and a new compressed-exponential scaling of dynamics, and determine the velocity distribution; by contrast, near the coverslip, dynamics scale differently, suggesting that bacterial motion near surfaces fundamentally differs from that of freely swimming organisms.
authors.affiliation: Department of Physics and SEAS, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Lu
authors.forename: Fabio
authors.initials: F
authors.lastname: Giavazzi
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Angelini
authors.forename: Emanuela
authors.initials: E
authors.lastname: Zaccarelli
authors.forename: Frank
authors.initials: F
authors.lastname: Jargstorff
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Schofield
authors.forename: James N
authors.initials: JN
authors.lastname: Wilking
authors.forename: Mark B
authors.initials: MB
authors.lastname: Romanowsky
authors.forename: David A
authors.initials: DA
authors.lastname: Weitz
authors.forename: Roberto
authors.initials: R
authors.lastname: Cerbino