A portable liquid-in-liquid extensional tester

A low-cost device designed to study filament thinning in the presence of a surrounding liquid is presented. Video analysis allows filament shape (diameter, curvature and reservoir behaviour) to be monitored. Results are reported for silicone oils with viscosities ranging from 0.5 to 5.0 Pa s in air, water, aqueous isopropanol mixtures and aqueous solutions of SDS, TX-100 (above and below the critical micelle concentration), human and bovine serum albumins. The evolution of filament diameter in these low Bond number tests exhibit viscous regime behaviour, with a transition between the Eggers (1993) and Papageorgiou (1995) results. In TX-100 and albumin solutions below the critical micelle concentration the thinning profiles suggest that mass transfer limitations affect the approach to filament breakup. At higher surfactant concentrations the reservoir shape deviates from that observed with clean solutions.