title: Spreading of blood drops over dry porous substrate: complete wetting case.
abstract: OBJECTIVE
  The process of dried blood spot sampling involves simultaneous spreading and penetration of blood into a porous filter paper with subsequent evaporation and drying. Spreading of small drops of blood, which is a non-Newtonian liquid, over a dry porous layer is investigated from both theoretical and experimental points of view.
  A system of two differential equations is derived, which describes the time evolution of radii of both the drop base and the wetted region inside the porous medium. The system of equations does not include any fitting parameters. The predicted time evolutions of both radii are compared with experimental data published earlier.
  
  
  RESULTS
  For a given power law dependency of viscosity of blood with different hematocrit level, radii of both drop base and wetted region, and contact angle fell on three universal curves if appropriate scales are used with a plot of the dimensionless radii of the drop base and the wetted region inside the porous layer and dynamic contact angle on dimensionless time. The predicted theoretical relationships are three universal curves accounting satisfactorily for the experimental data.
authors: Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, UK. Electronic address: T.Chao@lboro.ac.uk.
authors: Tzu Chieh
authors: TC
authors: Chao
authors: Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, UK. Electronic address: O.Arjmandi-Tash@lboro.ac.uk.
authors: Omid
authors: O
authors: Arjmandi-Tash
authors: Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, UK. Electronic address: d.b.das@lboro.ac.uk.
authors: Diganta B
authors: DB
authors: Das
authors: Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, UK. Electronic address: v.m.starov@lboro.ac.uk.
authors: Victor M
authors: VM
authors: Starov
mesh_terms: D055592:Biophysical Phenomena; D001769:Blood; D006801:Humans; D057446:Hydrodynamics; D008962:Models, Theoretical; D010209:Paper; D016062:Porosity; D012212:Rheology; D017155:Wettability
keywords: Blood; Capillary spreading; Dry blood spot sampling; Dry porous layer; Imbibition