Understanding emulsions and foams

Confocal image of two oil drops immobilized in an atomic force microscope. (top right) Schematic of the measurement where a custom micro-fabricated cantilever is used to hold the top drop in position. 

Vertical slices of a confocal microscopy image showing the profile of the two drops when separated far apart and when deformed.

October 2011

This project, led by Professor Ray Dagastine from the University of Melbourne, looks at fabricating nano- and micro-sizes devices to integrate with atomic force microscopy with the aim of developing new tools to study the complexity of interfaces in soft materials. The collisions between drops or bubbles in soft materials such as emulsions and foams control macroscopic behavior in growing sectors of biotechnology and nanotechnology as well as in materials used in everyday items. Some examples include the production of salad dressing, milk and shampoo, industrial processes such as solvent extraction used for pharmaceutical and mineral purification, as well as development of micro-fluidic devices for new applications.

The fabrication of custom designed micro-cantilevers allows the manipulation of oil drops or bubbles during these collisions to better understand the fundamental behaviors in emulsions and foams. Currently, these types of devices can only be fabricated internationally. In combination with the device fabrication, the atomic force microscope has been integrated with a laser scanning confocal microscopy to give real-time images of the collisions between drops and bubbles in high resolution. The nanoscale forces between these soft objects are sensitive to the addition of surfactants, polymers and biological molecules at these interfaces. This imparts a multilevel complexity and lateral heterogeneity starting at the molecular scale and spanning to the macroscopic scale. This complexity often creates a gap in our understanding of how these molecular structures mediate dynamic interfacial forces on the nanoscale and the material behavior on a large scale.