Rheology of a soft jammed interfacial solid

Particles adsorbed at an oil-water interface form a soft jammed solid, due to their long-range electrostatic repulsion. We measure the rheology of this material with a sensitive custom-built interfacial shear rheometer. The device uses permanent magnets to trap and control a needle that is adsorbed at the interface [Tajuelo et al., J. Rheol. 2016], with simultaneous microscopy that tracks the motions of individual particles in the material. We describe the instrument and present preliminary results on the evolution of the system's rheological properties as we "train" a memory in the system through oscillatory shear.