Slip of Newtonian Fluid in the Polymer Hydrogel Tube Wall

Poly(vinyl alcohol) (PVA) hydrogel tube was prepared from PVA-dimethylsulfoxide/water solution by repetitive cooling method. The inner surface of the PVA hydrogel tube was chemically modified with poly(acrylic acid) (PAA). Slip of Newtonian fluid in intact and modified PVA hydrogel tubes (sub-millimeter inner diameter) was studied. The slip was inferred by observing the motion of micron-sized spherical monodispersed polystyrene particles suspended in the flowing water by using an optical microscope from very low to medium flow rate. The particle velocity was estimated by both particle tracking (PT) and particle image deformation (PID) method and the slip velocity were measured by extrapolating the experimental data of the velocity profiles on the gel surfaces. Microscopic measurements reveal that the slip velocities on the hydrogel surfaces depended on the chemical nature and the surface roughness of the hydrogel surfaces and it was proportional to Reynolds number. Slip velocity of modified PVA hydrogel tube was higher than intact PVA hydrogel tube.