A novel method for interfacial rheology using an indirect interfacial rheometer

We have developed a system for performing interfacial rheology without attaching a probe directly to the interface itself. This indirect rheology is motivated by the applications of Pickering type systems, where rather than shear being applied directly to an interface, one of the continuous phases is sheared. The behaviour of the system as a whole is then governed, in part, by the rheology of that interface.
We use this setup to measure flow curves in a system of poly(methyl methacrylate) particles at a water/dodecane interface. The lack of a direct probe ensures two things: 1) we avoid substantial pre-shearing and 2) the response measured is due to the interface itself and not the probe [1].
In this indirect setup a shear is applied to the upper oil phase using a standard stress controlled rheometer. The response of the interface is then measured by confocal microscopy. A range of rheological behaviour is observed dependent on surface coverage, shear rate and surface structure. The direct visualisation of the interface allows all of these input parameters to be measured and various flow curves can be produced to observe their effect on the rheology of the interface.
[1] R. Van Hooghten et al, Langmuir 33, 4107 (2017)