(440c) Probing Adhesive Emulsions As a Function of Polymer and Surfactant Composition Via a Novel Microfluidic Platform

Attractive interactions between drops in which aggregation, rather than coalescence occurs, lead to the formation of aggregates, gels or microstructures that then control the phase behaviour, stability, rheology and most importantly function of formulated products (e.g., food, personal care products, pharmaceutical formulations). These forces are often highly system specific and are a function of a number of additive components. Previously, we developed a microfluidic platform to probe surface forces between drops with strong adhesive interactions. For a specific polymer-surfactant (PS) complex we correlated the adhesive interactions observed the microfluidic device with surface forces measured between micro-drop pairs using atomic force miscopy. The microfluidic device forms 1-dimensional structure, i.e. chains of drops, where the strength of the adhesion forces measured via AFM correlated to the length of the chains of drops in the microfluidic device.

In this talk, we discuss the application and development of these devices to correlate drop adhesion for a number of PS complexes. These devices are now capable of measuring thousands to tens of thousands of observations allowing for the development of drop chain length distributions to define a system specific adhesive fingerprint. We will discuss results that compare the adhesive behaviour for different polymers as a function of surfactant composition. The device also allows for step changes in solution conditions to observe the responsive nature of many PS complexes to changes in surfactant and electrolyte concentration. We will also touch on a series of benchmark studies including a novel small angle neutron scattering (SANS) study using these microfluidic devices and in-situ interfacial tension measurements.