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Bubbling down: Discovery suggests surprising uses for common bubbles

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 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.

With the aim of contributing to the sustainability of society, Kao Corporation promotes research activities for forward-looking environmental technologies, centring on advanced use of biomass, at the Eco Technology Research Centre in the Wakayama Plant. In the research on algae, which is one of the major themes in this field, the company succeeded to find enzyme that can produce a large number of medium chain fatty acids-the main components of natural fats and oils (e.g. palm kernel oils and coconut oils), which are raw materials for surfactants in detergents, shampoos, and other related products. This finding presented a strong possibility that Kao, as a world pioneer, could acquire a non-edible raw material source of fats and oils that is natural and not consumed as food. The company will pursue the technological development for the production of fats and oils from algae with the aim of technical production. Reportedly, potential for algae to produce fats and oils is more than ten times that of such natural resources as palm. In recent years, many research cases are reported on production of fats and oils, containing C16 to 18 fatty acids as a main component, to acquire new raw materials for fuels (biofuels) in replacement of fossil fuels. However, surfactants in detergents and shampoos and the base substances of various raw materials are C12 to 14 medium chain fatty acids. Therefore, the conventional scope of research on algae could not have been sufficiently applied. The company found some strains that contained a large number of C12 medium chain fatty acids in C12 to 14 medium chain fatty acids through research activity on biotechnologies, which evolved from technologies involving enzymes for detergents. Additionally, as a first in the field of algae, the company identified a novel acyl-ACP thioesterase with high specificity to medium chain fatty acids from the genus Nannochloropsis. Kao expects that these findings will dramatically accelerate the breeding development of algae for large-scale production of medium chain fatty acids.

Skinvisible Pharmaceuticals, Inc. has announced the forming of Kintari, a new wholly-owned subsidiary to market a premium line of scientifically formulated skincare products powered by the company's patented Invisicare® technology. As part of the Company's strategic focus on revenue generation and creating shareholder value, Kintari will be a direct sales company that will launch products initially in the United States and Canada. The Kintari product portfolio consists of "Youth Renewed" (YR) anti-aging products to help fight the signs of aging. The Kintari YR product line will include a rejuvenating day cream and a renewing night cream. These products have been developed using proven anti-aging ingredients with scientific evidence of their effectiveness at reducing the look of fine lines and wrinkles resulting in youthful looking skin. These potent ingredients will be powered by our patented Invisicare technology, providing consumers with unique, effective products, which cannot be duplicated. Additional products will be added to enhance this product line as the company grows and expands. Skinvisible has selected the direct sales model for Kintari products as it enables the Company to reach consumers directly and effectively with superior products formulated with the benefits of Invisicare.

When people with sensitive skin come into contact with irritants, that often means that their skin burns or prickles and sometimes you can see redness or areas of flaking. Beiersdorf R&D has gotten to the bottom this phenomenon and discovered the active ingredient SymSitive to sooth very sensitive skin. It stops irritation before it’s felt and calms nerves in the skin and that’s why it’s in all the products of the Eucerin UltraSENSITIVE and AntiREDNESS care series. “My team studied sensitive skin very carefully in recent years and discovered notable differences from normal skin” says Dr. Gitta Neufang, Head of R&D Medical Management at Beiersdorf. “Sensitive skin reacts much stronger to irritants. We used capsaicin, the pungent component of black pepper to mimic skin irritation”. When capsaicin is applied to the skin surface it activates a protein on sensory nerve fibre endings, the TRPV1 channel. After bonding, the channel becomes permeable to calcium ions that then flow into the nerve fibres, transferring the irritation further along the fibres until it can be felt. “We have tested a series of ingredients to see if they can prevent this calcium stream caused by capsaicin and the irritation that results from it,” Neufang explains and adds: “SymSitive was clearly the best. When used nerve fibres hardly reacted at all and the irritation was not transferred further”. Studies on test subjects also confirm that SymSitive has a calming effect on very sensitive skin: the prickling or burning sensation of the skin from the irritant capsaicin is soothed just minutes after using SymSitive-containing products or doesn’t even occur when SysmSitive is used beforehand. Nerve fibres after being irritated by capsaicin with calcium ions flowing in (green). Nerve fibres after pre-treatment with SymSitive and subsequent irritation with capsaicin. This intensive skin research – the systematic search for ingredients in a lab and proving their effectiveness in test subject studies are the basis of the care series EUCERIN UltraSENSITIVE and AntiREDNESS. “The results are very positive and seem to speak for themselves. The products can noticeably and sustainably help people with hypersensitive skin” says Dr. Gitta Neufang head of R&D Medical Management at Beierdorf. This is good news for the up to 70 percent of women who describe their skin as very sensitive.