Spreading of blood drops over dry porous substrate: Complete wetting case

Abstract

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.

Simultaneous spreading and imbibition of blood droplets over porous substrates in the case of partial wetting

“…Earlier [16,17] the spreading behaviour of blood on commercial DBS filter paper has been investigated in the case of complete wetting. Below the spreading/imbibition in the case of partial wetting is investigated.…”

“…Porcine blood was collected in EDTA anti-coagulated tubes (International Scientific Supplies Ltd. Bradford, UK) from a local butcher and treated to have different haematocrit levels [16,17]. The blood samples of two different haematocrit levels, 30% and 50% were chosen and used in the spreading experiments.…”

“…The permeability of porous substrate and effective capillary pressure are considered as a single coefficient in our previous theoretical model for the complete wetting case [16]. This coefficient was obtained from the permeability experiments based on the modified Darcy's law.…”

“…However, there are some disadvantages in the DBS process, such as, unequal distribution, haematocrit effects and analytes extraction, which limited the application of DBS for high sensitive and quality analysis [1,2,4,6,[13][14][15]. Although, new developments and application of DBS have been intensively studied from both experimental and clinical points of view, hydrodynamics of spreading/imbibition of blood in the course of sampling was investigated only recently [16,17].…”

“…However, the spreading and wetting condition of a drop on a porous substrate are obviously different due to the presence of a porous layer. This process has been investigated recently in the case of spreading/imbibition of Newtonian liquids [20,21] and in the case of blood spreading/imbibition [16,17] in the case of complete wetting.…”