(Press-News.org) Anyone who has ever had a glass of fizzy soda knows that bubbles can throw tiny particles into the air. But in a finding with wide industrial applications, Princeton researchers have demonstrated that the bursting bubbles push some particles down into the liquid as well.
"It is well known that bursting bubbles produce aerosol droplets, so we were surprised, and fascinated, to discover that when we covered the water with oil, the same process injected tiny oil droplets into the water," said Howard Stone, the Donald R. Dixon '69 and Elizabeth W. Dixon Professor of Mechanical and Aerospace Engineering at Princeton and the lead researcher for the project.
The conclusions provide new insight into the mixture of non-soluble liquids — a process at the center of many fields from drug manufacturing to oil spill cleanups.
In an article published on July 13 in the scholarly journal Nature Physics, the researchers describe how they reached their conclusions after examining bubbles in containers holding water covered by a layer of oil. Using several experimental approaches, they presented a detailed physical description of how the bubbles burst and how that affected the oil and water mix.
"If you look at this system, which has a thin layer of oil over water, the bursting bubbles were dispersing the oil phase in the form of nano-droplets into the water," said Jie Feng, a graduate student in Stone's lab and the lead author of the paper. "Essentially, it is an unrealized form of mass transport related to bubble bursting."
In one observation, the researchers noted that the water in one container changed from clear to translucent after bubbles ran through the mixture for some time. The change in appearance "suggested that small objects had been dispersed in the lower water phase," the researchers wrote.
To get a better understanding of how this was happening, they used a high-speed camera to break down the steps involved in a bubble's final pop. They found that a bubble's collapse caused a pressure wave just below the bubble; this wave pushed a small amount of liquid out and down, away from the collapsing void.
The researchers also found that the addition of a surfactant, which decreases surface tension, was critical to the formation of the nano-droplets. In fact, they concluded that without a proper amount of surfactant, the droplets would not form.
The nano-droplets are so small they are impossible to see with the naked eye, so the researchers performed further experiments to test their analysis. In one, they spread an extremely thin layer of latex particles over the water and were able to observe the particles moving into the water. They also added a layer of material that is sensitive to ultraviolet light and then used the light to solidify the droplets for observation in the water mixture.
Bubbles' ability to mix liquids offers insights into a number of important systems. During oil spills, for example, it is important to understand how the oil moves from the surface of the water into deeper layers. This has generally been attributed to wave action, but the researchers' findings indicate that even in a flat calm the oil can gradually filter down into the water because of tiny bubbles.
"Bubbles are used to make foams and are part of common gas-liquid processes used in chemical processing," Stone said. "But bubbles also occur in lakes, rivers and oceans because of wave breaking and rain. As a consequence, bubbles can impact many systems."
The researchers said that bubbling also might play a role in a critical system in which organic matter circulates through the ocean. A thin film of material, called the sea surface microlayer, rests at the very top of ocean water. The microlayer contains lipids, proteins and hydrocarbon pollutants.
"Our work suggests that the sea surface microlayer may not only be transported into the atmosphere within aerosol droplets produced by bursting bubbles, but it might also be dispersed into the bulk of the oceans, thus redistributing organic matter into the ecosystem," they wrote.
Feng also said that applying this approach could play an important role in many industrial mixing systems. For one, this manner of bubbling to produce nanoemulsions uses much less energy than traditional mixers, so it is cheaper and more efficient. It also does not require extremely low surface tensions, which some types of industrial processes require. And it provides a good method to mix typically insoluble liquids, such as oil and water.
"This system offers an energy-efficient route to produce nanoparticles, with the potential to increase in scale, for applications in a variety of fields such as drug delivery, food production and materials science," he said.
INFORMATION:
Besides Stone and Feng, the project researchers included Matthieu Roche and Daniele Vigolo (now research associates in Paris and Zurich, respectively) who worked as postdoctoral researchers in Princeton's Department of Mechanical and Aerospace Engineering; Luben Arnaudov and Simeon Stoyanov, of Unilever Research and Development; and Theodor Gurkov and Gichka Tsutsumanova, of Sofia University, Bulgaria.
Support for the research was provided in part by grant from the Consortium for the Molecular Engineering of Dispersant Systems funded by the BP/Gulf of Mexico Research Initiative, and the European Union's Beyond Everest project.
Bubbling down: Discovery suggests surprising uses for common bubbles
2014-08-19
ELSE PRESS RELEASES FROM THIS DATE:
Perampanel for epilepsy: Still no proof of added benefit
2014-08-19
The drug perampanel (trade name Fycompa) has been approved since July 2012 as adjunctive ("add-on") therapy for adults and children aged 12 years and older with epileptic fits (seizures). In a new early benefit assessment according to the Act on the Reform of the Market for Medicinal Products (AMNOG), the German Institute for Quality and Efficiency in Health Care (IQWiG) examined whether perampanel offers an added benefit over the appropriate comparator therapy. However, such an added benefit cannot be derived from the new dossier either, as the drug manufacturer did not ...
Ruxolitinib for myelofibrosis: Indication of considerable added benefit
2014-08-19
Ruxolitinib (trade name: Jakavi) has been approved since August 2012 for the treatment of adults with myelofibrosis. In an early benefit assessment pursuant to the Act on the Reform of the Market for Medicinal Products (AMNOG), the German Institute for Quality and Efficiency in Health Care (IQWiG) examined whether this new drug offers an added benefit over the appropriate comparator therapy specified by the Federal Joint Committee (G-BA).
According to the results, there is an indication of considerable added benefit in comparison with "best supportive care" (BSC) because ...
College education not always about what you have, but how you use it
2014-08-19
Students who have books and computers at home, who take extramural cultural classes, and whose parents give advice and take part in school activities are most likely to enroll for a four-year college degree. Also, more American black students – irrespective of their class or background – will set off on this education path than their white counterparts. So says David Merolla of Wayne State University and Omari Jackson of Colby-Sawyer College in the US, in Springer's journal Race and Social Problems. Merolla and Jackson studied class and race differences in college enrollment, ...
Organic photovoltaic cells of the future
2014-08-19
WASHINGTON D.C., Aug. 19, 2014 – Organic photovoltaic cells -- a type of solar cell that uses polymeric materials to capture sunlight -- show tremendous promise as energy conversion devices, thanks to key attributes such as flexibility and low-cost production.
But one giant hurdle holding back organic photovoltaic technologies have been the complexity of their power conversion processes, which involve separate charge formation and transport processes.
To maneuver around this problem, a team of researchers in Japan has developed a method to determine the absolute value ...
Love makes sex better for most women
2014-08-19
Love and commitment can make sex physically more satisfying for many women, according to a Penn State Abington sociologist.
In a series of interviews, heterosexual women between the ages of 20 and 68 and from a range of backgrounds said that they believed love was necessary for maximum satisfaction in both sexual relationships and marriage. The benefits of being in love with a sexual partner are more than just emotional. Most of the women in the study said that love made sex physically more pleasurable.
"Women said that they connected love with sex and that love actually ...
Life on Mars? Implications of a newly discovered mineral-rich structure
2014-08-19
New Rochelle, August 19, 2014—A new ovoid structure discovered in the Nakhla Martian meteorite is made of nanocrystalline iron-rich clay, contains a variety of minerals, and shows evidence of undergoing a past shock event from impact, with resulting melting of the permafrost and mixing of surface and subsurface fluids. Based on the results of a broad range of analytical studies to determine the origin of this new structure, scientists present the competing hypotheses for how this ovoid formed, point to the most likely conclusion, and discuss how these findings impact the ...
Women will benefit from the Affordable Care Act's contraceptive coverage
2014-08-19
Women could benefit greatly from the Affordable Care Act's mandate for contraceptive coverage, according to Penn State College of Medicine researchers.
The Affordable Care Act requires private insurance plans -- except those grandfathered or exempted due to employers' religious beliefs -- to provide women with access to all FDA-approved contraceptive methods without cost-sharing. This first-dollar coverage "has the potential to dramatically shift contraceptive use patterns, to reduce the U.S. unintended pregnancy rate ... and to improve the health of women and families," ...
Evolution of marine crocodilians constrained by ocean temperatures
2014-08-19
The ancestors of today's crocodiles colonised the seas during warm phases and became extinct during cold phases, according to a new Anglo-French study which establishes a link between marine crocodilian diversity and the evolution of sea temperature over a period of more than 140 million years.
The research, led by Dr Jeremy Martin from the Université de Lyon, France and formerly from the University of Bristol, UK is published this week in Nature Communications.
Today, crocodiles are 'cold-blooded' animals that mainly live in fresh waters but two notable exceptions, ...
Electrical engineers take major step toward optical computing
2014-08-19
Edmonton—The invention of fibre optics revolutionized the way we share information, allowing us to transmit data at volumes and speeds we'd only previously dreamed of.
Now, electrical engineering researchers at the University of Alberta in Edmonton, Alberta, Canada are breaking another barrier, designing nano-optical cables small enough to replace the copper wiring on computer chips.
This could result in radical increases in computing speeds and reduced energy use by electronic devices.
"We're already transmitting data from continent to continent using fibre optics, ...
NASA sees Tropical Storm Karina losing its punch
2014-08-19
Tropical Storm Karina continues to weaken in the Eastern Pacific over open waters, and NASA data shows there's not much punch left in the storm.
NASA's Tropical Rainfall Measuring Mission or TRMM satellite can measure the rate of rainfall from its orbit in space and when it passed over Tropical Storm Karina in the Eastern Pacific it saw an isolated area of heavy rain remaining in the storm.
Tropical Storm Karina weakened during the overnight hours and by Tuesday, August 19, maximum sustained winds had decreased to near 60 mph (95 kph). When TRMM passed overhead at 03:04 ...