title: Creep compliance rheology with a probe-like cylindrical geometry.
abstract: Rheology experiments have been performed on the vitreous humor, a soft gel that rests inside of the eye, to study its viscoelastic behavior and underlying macromolecular structure. A significant challenge for experimentalists is preserving the macromolecular structure when removing vitreous from in vivo conditions.
  
  
  
  We have developed a novel probe-like rheometer geometry that allows us to perform shear rheology experiments on the vitreous humor in situ. The aim of this study is to assess the feasibility of the probe geometry.
  
  
  
  Creep compliance responses of silicone oils, Xanthan gum solutions, and bovine and porcine vitreous humor were measured using the probe geometry and compared to measurements performed with standard geometries.
  
  
  
  Viscosities calculated from the creep responses of silicone oils closely match between the probe and standard geometry. Viscosities and creep compliance values of Xanthan gum measurements achieve order of magnitude agreement between the probe and standard geometry. Significant differences are detected with the probe between bovine and porcine vitreous (p<0.001).
  
  
  
  These results suggest the probe may feasibly measure viscosities of Newtonian fluids, and correctly detect differences in the creep response of complex fluids with varying viscoelastic behaviors.
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of California Los Angeles, CA, USA.
authors.forename: Kelly
authors.initials: K
authors.lastname: Connelly
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of California Los Angeles, CA, USA.
authors.forename: Pooria
authors.initials: P
authors.lastname: Sharif-Kashani
authors.affiliation: Stein Eye Institute, Department of Ophthalmology, University of California Los Angeles, CA, USA.
authors.forename: Matt
authors.initials: M
authors.lastname: Farajzadeh
authors.affiliation: Stein Eye Institute, Department of Ophthalmology, University of California Los Angeles, CA, USA.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Hubschman
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of California Los Angeles, CA, USA.
authors.forename: H Pirouz
authors.initials: HP
authors.lastname: Kavehpour
mesh_terms: D000818:Animals; D002417:Cattle; D004548:Elasticity; D006801:Humans; D012212:Rheology / Q000379:methods*; D014783:Viscosity; D014822:Vitreous Body / Q000254:growth & development* / Q000473:pathology
keywords: Eye; biorheology; viscoelasticity; vitreous gel