title: Two-particle microrheology of quasi-2D viscous systems.
abstract: We study the spatially correlated motions of colloidal particles in a quasi-2D system (human serum albumin protein molecules at an air-water interface) for different surface viscosities eta s. We observe a transition in the behavior of the correlated motion, from 2D interface dominated at high eta s to bulk fluid dependent at low eta s. The correlated motions can be scaled onto a master curve which captures the features of this transition. This master curve also characterizes the spatial dependence of the flow field of a viscous interface in response to a force. The scale factors used for the master curve allow for the calculation of the surface viscosity eta s that can be compared to one-particle measurements.
authors.affiliation: Department of Physics, Emory University, Atlanta, Georgia 30322, USA.
authors.forename: V
authors.initials: V
authors.lastname: Prasad
authors.forename: S A
authors.initials: SA
authors.lastname: Koehler
authors.forename: Eric R
authors.initials: ER
authors.lastname: Weeks
mesh_terms: D019840:2-Propanol / Q000737:chemistry; D000388:Air; D003102:Colloids / Q000737:chemistry*; D004058:Diffusion; D006801:Humans; D008956:Models, Chemical; D012212:Rheology / Q000379:methods*; D012709:Serum Albumin / Q000737:chemistry; D012996:Solutions; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D003102:Colloids; D012709:Serum Albumin; D012996:Solutions; D014867:Water; D019840:2-Propanol