  We have developed an experimental method to perform interfacial rheology on
liquid/liquid interfaces with no tool attached directly to the interface. This
is achieved by shearing one of the liquid phases and measuring the interfacial
response via confocal microscopy. Using this method we have measured steady
shear material parameters such as the interfacial viscosity for fluid-like
interfaces, and the interfacial elastic modulus for interfaces with solid-like
behaviour. These measurements are in line with recent measurements made on
similar systems using a conventional probe. Moreover, using our method we are
able to measure lower interfacial viscosities than those that have previously
been reported. This indirect method lends itself to microscopic structural
analysis, as well as macroscopic rheological analysis, due to simultaneous
microscopy. Our analysis shows that the interfacial behaviour is strongly
dependent on the surface coverage and surface structure, and steady shear can
have an irreversible effect on the structure of an interface.
