One stabilizer, many emulsions
Scientists Michele Zanini, Claudia Marschelke, Svetoslav E. Anachkov, Emanuele Marini, Alla Synytska, and Lucio Isa published their work earlier this year in the online open access journal Nature Communications. The article, titled, ‘Universal emulsion stabilization from the arrested adsorption of rough particles at liquid-liquid interfaces’ describes how they went about developing a roughly surfaced particle that will stabilize both oil-in-water emulsions and water-in-oil emulsions.
The research team, from universities in Switzerland, Germany, and Bulgaria, began with the premise that “surface heterogeneities, including roughness, significantly affect the adsorption, motion and interactions of particles at fluid interfaces,” according to the article abstract.
In an effort to compile data correlating surface textures to wettability, the researches went ahead and “[synthesized] a library of all-silica microparticles with uniform surface chemistry, but tuneable surface roughness and study their spontaneous adsorption at oil–water interfaces.”
The team found that rough particles, with a texture similar to that of a raspberry, can stabilize multiple types of emulsions because of how the particles contact the various droplets. “If the researchers add the particles to the oil phase, a water-in-oil emulsion is formed. Conversely, they are able to stabilise an oil-in-water emulsion (oil droplets finely dispersed in water), if they dissolve their new particles in water first,” explains a press release about the research from ETH Zurich.
Why the textured particles are able to do this, says Isa (who’s the lead researcher on this project), is that “although they push forward on the surface between the liquids, they cannot move as far across it as comparable silica particles with a smooth surface do - the rough particles get stuck before they can reach the energetically most favourable position at the interface.”
And it’s this getting stuck that “imparts tremendous contact angle hysteresis, which can practically invert the particle wettability for sufficient roughness, irrespective of their chemical nature,” explains the abstract.
Through this project, the researchers learned more about the connection between particle texture and wettability and this knowledge can be applied to future emulsifier design. “These particles can therefore be used as a universal tool for creating emulsions,” Isa says in the press release.
“Even though this research was focused on laboratory model systems,” notes the release, “the same principles can be extended to the use of naturally occurring rough particles as emulsion stabilisers, to find other potential uses in the food, cosmetics and pharma industry, even though further research is needed in this direction.”
Find the full-text article here.