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

The sampling process of dried blood spot (DBS) is spreading of blood, which is Non-Newtonian fluid, over porous substrates. Spreading/imbibition behaviour of blood samples over Whatman 903 filter paper in complete wetting case has been investigated earlier (Tzu Chieh Chao et al., 2015). The spreading behaviour of DBS sampling has been investigated below in the case of partial wetting. Nitrocellulose membranes (NCM) with different pore size and silanized Whatman 903 blood saving card have been used as porous substrates. The spreading experiments have been applied to obtain the time evolution of spreading parameters, such as, radius of droplet base, dynamic contact angle and radius of the wetted region. The result of spreading on NCM showed that the spreading process was a partial wetting spreading. A separation of red blood cells (RBCs) and blood plasma has been found in the case of the blood drop spreading over 0.2 and 3.0 μm NCMs. Important that while the RBCs were not damaged in this process. This opens a completely new opportunity to (1) investigate RBCs and plasma separately; (2) to use this method for non-destructive separation of living cells from aqueous solution