Jamming modulates coalescence dynamics of shear-thickening colloidal droplets

Recent investigations into coalescence dynamics of complex fluid droplets revealed the existence of sub-Newtonian behaviour for polymeric fluids (elastic and shear thinning). We hypothesize that such delayed coalescence or sub-Newtonian coalescence dynamics may be extended to the general class of shear thickening fluids. To investigate this droplets of aqueous corn-starch suspensions were chosen and its coalescence in sessile pendant configuration was probed by high-speed real time imaging. Temporal evolution of the neck (growth) during coalescence was quantified as a function of suspended particle weight fraction φ_w. The necking behaviour was found to evolve as the power-law relation $R=a{t}^b$ where R is neck radius with exponent $\text{b}\le 0.5$ implying it is a subset of the generic sub-Newtonian coalescence. Second significant delay in the coalescence dynamics is observed for particle fractions beyond the jamming fraction {\ φ}_w>\ φ_J\geq0.35}. Our proposed theoretical model captures this delay implicitly through altered suspension viscosity stemming from increased particle content.