Response of capillary suspensions to external deformations

When a small amount (less than 1%) of a second immiscible liquid is added to the continuous phase of a suspension, the rheological properties of the mixture are dramatically altered from a fluid-like to a gel-like state or from a weak to a strong gel and the strength can be tuned in a wide range covering orders of magnitude [1]. The present work uses a model system to investigate the complex flow behavior of a capillary state suspension (where the secondary fluid does not preferentially wet the particles) using linear and nonlinear rheology concentrating the aging of on the network structure. Power-law aging behavior is observed for very long times with a small, but positive exponent. These admixtures also show significant time varying behavior during forced aging, with an initial increase in the network strength and then a sudden decrease in the strength as the network is destroyed. Our results provide a possible route to fingerprint the material behavior of capillary state suspensions. [1] E. Koos and N. Willenbacher, Science 331 (2011) 897.status: publishe