title: Rheological microscopy: local mechanical properties from microrheology.
abstract: We demonstrate how tracer microrheology methods can be extended to study submicron scale variations in the viscoelastic response of soft materials; in particular, a semidilute solution of lambda-DNA. The polymer concentration is depleted near the surfaces of the tracer particles, within a distance comparable to the polymer correlation length. The rheology of this microscopic layer alters the tracers' motion and can be precisely quantified using one- and two-point microrheology. Interestingly, we found this mechanically distinct layer to be twice as thick as the layer of depleted concentration, likely due to solvent drainage through the locally perturbed polymer structure.
authors.affiliation: Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Chen
authors.forename: E R
authors.initials: ER
authors.lastname: Weeks
authors.forename: J C
authors.initials: JC
authors.lastname: Crocker
authors.forename: M F
authors.initials: MF
authors.lastname: Islam
authors.forename: R
authors.initials: R
authors.lastname: Verma
authors.forename: J
authors.initials: J
authors.lastname: Gruber
authors.forename: A J
authors.initials: AJ
authors.lastname: Levine
authors.forename: T C
authors.initials: TC
authors.lastname: Lubensky
authors.forename: A G
authors.initials: AG
authors.lastname: Yodh
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics; D004279:DNA, Viral / Q000737:chemistry*; D004548:Elasticity; D005456:Fluorescent Dyes / Q000737:chemistry; D008853:Microscopy / Q000379:methods*; D008956:Models, Chemical; D011137:Polystyrenes / Q000737:chemistry*; D012212:Rheology / Q000379:methods*; D012235:Rhodamines / Q000737:chemistry; D014783:Viscosity
chemical_list: D004279:DNA, Viral; D005456:Fluorescent Dyes; D011137:Polystyrenes; D012235:Rhodamines