Navigation Links
Slow road to stability for emulsions
Date:12/9/2011

Cambridge, Mass. -- By studying the behavior of tiny particles at an interface between oil and water, researchers at Harvard have discovered that stabilized emulsions may take longer to reach equilibrium than previously thought.

Much longer, in fact.

"We were looking at what we thought would be a very simple phenomenon, and we found something very strange," says principal investigator Vinothan Manoharan, Associate Professor of Chemical Engineering and Physics at the Harvard School of Engineering and Applied Sciences (SEAS).

"We knew that the particle would stick to the interface, and other researchers had assumed this event happened instantaneously," he says. "We actually found that the timescale for this process was months to years."

The findings, published in Nature Materials (online) on December 4, have important implications for the manufacturing processes used in pharmaceuticals, cosmetics, and foods, among other chemical industries.

An emulsion is a mixture of two or more insoluble liquidsusually oil and water. A simple emulsion like vinaigrette takes energy to create (for example, by shaking it), and over time it will separate out, as the oil or water molecules cluster together again.

To give products like mayonnaise and sunscreen a reasonable shelf life, manufacturers typically add stabilizing particles to create Pickering emulsions. Ice cream, for example, is stabilized by tiny ice crystals that cling to the interfaces between the fat and water droplets, creating a rigid physical barrier between the two. In traditional mayonnaise, proteins from the egg yolk perform the same role.

When the oil and water in these types of emulsions are completely mixed and stable, the particles are said to be at equilibrium.

"There are certain rules for making different types of emulsions," explains Manoharan. "For example, do you get oil droplets in water, or water droplets in oil? The conventional rules are based on the properties of the materials, but our results suggest that it also has to do with time and the energy you put into the system."

To study Pickering emulsions, Manoharan and his colleagues used holography to gain a three-dimensional view of microscopic polystyrene balls while they approached an interface between oil and water. The researchers used light from a focused laser (optical tweezers) to gently push a particle toward the interface, hoping to watch it settle into its predicted equilibrium point, straddling the oil-water boundary.

To their surprise, none of the particles reached equilibrium during the experimental timeframe. Instead, they breached the interface quickly, but then slowed down more and more as they crossed into the oil. Mathematically extrapolating the logarithmic behavior they did observe, Manoharan's team discovered that the particles would stabilize on a time frame much longer than anyone had predicted.

"Our experiments only went on for a few minutes, but for the system to reach equilibrium would take at least weeks to months, and possibly years," explains lead author David Kaz, Ph.D. '11, who earned his degree in physics at Harvard's Graduate School of Arts and Sciences.

The finding is unlikely to affect any time-tested culinary recipes, but many other applications rely on very precise predictions of the particles' behavior.

In biomedical engineering, for example, Pickering emulsions are used to create colloidosomesmicroscale capsules that could deliver precise concentrations of drugs to specific targets in the human body. Understanding the behavior of particles at liquid interfaces is also relevant to many aspects of chemical engineering, water purification, mineral recovery techniques, and the manufacture of nanostructured materials.

The new research suggests that the models currently used to predict and optimize these systems may be too simplistic.

"It has always been assumed that the particles moved almost instantly to their equilibrium contact angle or height, and then Young's law would apply," says co-author Michael Brenner, Glover Professor of Applied Mathematics and Applied Physics at SEAS. "What we found, though, is that equilibrium might take much, much longer to achieve than the time scale at which you're using your product."

"If you're really stirring hard, maybe you can get the particles to reach equilibrium faster," Brenner adds, "But what we're saying is that the process matters."


'/>"/>
Contact: Caroline Perry
cperry@seas.harvard.edu
617-496-1351
Harvard University
Source:Eurekalert  

Related biology news :

1. Genomic architecture presages genomic instability
2. NYU Langone researchers reveal a new mechanism of genomic instability
3. Study shows stability and utility of floating wind turbines
4. Measuring the stability of organic waste
5. Indiana U. at APHA: Studies about health education for people with ID, stability balls at work
6. AAPS and PhRMA co-sponsor stability workshop
7. Scientists find universal rules for food-web stability
8. Corn yield stability varies with rotations, fertility
9. The downside of microtubule stability
10. Temporary infidelity may contribute to the stability of ancient relationships
11. Microtest Labs Adds Dissolution Testing to its Suite of Analytical and Stability Testing Services
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Slow road to stability for emulsions
(Date:2/8/2017)...  Aware, Inc. (NASDAQ: AWRE ), a leading ... for its quarter and year ended December 31, 2016. ... $3.9 million compared to $6.9 million in the same quarter ... was $0.6 million compared to $2.6 million in the fourth ... 2016 was $0.5 million, or $0.02 per diluted share, which ...
(Date:2/8/2017)... Report Highlights The global biosurgery ... billion in 2016 at a compound annual growth rate ... Includes - An overview of the global market for ... from 2015 and 2016, and projections of compound annual ... market on the basis of product type, source, application, ...
(Date:2/7/2017)... LONG BEACH, New York , February 7, 2017 ... formerly known as ID Global Solutions Corporation [OTC: IDGS], ... identification, identity management and electronic transaction processing services, is ... a reorganization of the Company. Effective January ... Chairman of the Board of Directors, CEO and President. ...
Breaking Biology News(10 mins):
(Date:2/24/2017)... ... 24, 2017 , ... Chef Jodi Abel has returned from her three-week ... cities, she gained a number of delicious recipes and new techniques to share with ... Africa’s Western Cape province. It is internationally renowned for its incredible wine farms, ...
(Date:2/24/2017)... DIEGO , Feb. 24, 2017  Aethlon Medical, ... following note authored by its Chairman and CEO, ... at the Munich Security Conference last Saturday, Bill ... virus could kill more people than nuclear weapons. Mr. ... U.S. and U.K. intelligence agencies, that scientific terrorists have ...
(Date:2/24/2017)... , Feb. 24, 2017  Driven by ... biotechnology are now the fastest growing categories, finds ... Specialty Actives in Personal Care: Multi-regional Market Analysis ... and management consulting firm Kline. "Biotechnology ... that make them more effective for skin and ...
(Date:2/24/2017)... ... ... FireflySci, Inc is an explosive small business that continues to grow at ... their powerful cuvette and spectrophotometer calibration to the spectroscopy world. Now ... as they add yet another mark on the global map. , With distributors in ...
Breaking Biology Technology: