270403 Nano-Mechanical Properties of Clay Armoured Emulsion Drops As a Function of Solution Conditions
Solid-stabilized emulsions have received increasing attention over the last two decades due to their superior stability when compared to traditional surfactant stabilized emulsions. These emulsions can be found in a wide range of industries such as food, pharmaceutical, paint and petrochemical. Non-spherical particles such as plate-like or needle-like have had more recent attention and it has been shown that they can stabilize emulsions at a much lower solids volume fraction than spherical particles. Clay platelets, have been used as stabilizers in emulsions and bubbles and are common to many dispersions. Clay-stabilized bubbles, or armoured bubbles, have been shown to be very robust behaviour in water and other liquids, and show evidence of size selective permeability, i.e. they are semi-porous1.
Here, the mechanical properties of clay-armoured emulsion droplets were investigated using laser scanning confocal microscopy with an in situ atomic force microscopy measurement2. This combination allows the visualization of droplet shape as a function of applied force. The emulsion droplets were found to be mechanically robust, stable against coalescence during drop collisions and able to recover from large deformations without disintegration. A Hookean constitutive law was used to extract the surface Young’s modulus of the clay-armoured droplets as a function of a range of solution conditions. The clay-armoured droplets were relatively insensitive to changes in solution ionic strength, pH and the addition of surfactant. The elasticity measurements in this study should help illuminate the impact of the clay-armoured droplets on macroscopic properties of emulsions including rheological properties and emulsion stability.
- A. B. Subramanian, J. Wan, A. Gopinath and H. A. Stone, Soft Matter, 2011, 7, 2600-2612.
- S.-Y. Tan, R. F. Tabor,. L. Ong, G. W. Stevens, and R.R. Dagastine, Soft Matter, 2012, 8, 3112-3121.