Shear-induced effects in confined non-Newtonian fluids under tension

We study the influence of shear effects on the adhesive performance of a non-Newtonian fluid under tension, confined between two parallel flat plates. The upper plate is subjected to a pulling force, which is recorded during the separation process. We approach the problem analytically, and use a modified Darcy's law in the weak shear limit to derive the adhesive force and the separation energy. Our theoretical results demonstrate that, for relatively small separations, the adhesion strength is considerably reduced (enhanced) if the fluid is shear thinning (thickening). For larger plate separations, shear effects become negligible, and usual Newtonian behavior is observed. These findings are confirmed by a numerical solution of a more realistic version of the problem, which considers weak shear effects, plus the intrinsic elasticity of the lifting apparatus.