It was a question that has kept physicists and chemists busy for more than twenty years. Why can tiny bubbles in a liquid supersaturated with gas remain stable for weeks, while according to theoretical expectation they should disappear in a fraction of a second? Prof. dr. ir. Detlef Lohse from the University of Twente's MESA+ research institute found the answer. The research was recently published in the scientific journal Physical Review E (Rapid Communication).
If a water repellent substrate is immersed in water containing dissolved gas, tiny bubbles can form on the immersed body. These so called surface nanobubbles emerge because the surrounding liquid wants to lose its gas, similar as bubbles emerge in a glass of soda.
In the case of the nanobubbles, however, the bubbles are only ten to twenty nanometres in height (one nanometre is one million times smaller than a millimetre), and therefore the (Laplace) pressure in the bubble is very high. According to all the current theories, the bubbles should disappear on their own accord in less than a millisecond, since the gas in the bubbles wants to dissolve in the water again.
According to Lohse, this idea is quite similar to a balloon, which - even if it is properly tied - always deflates over time. The reason for this is that a little bit of air constantly leaks through the rubber of the balloon due to diffusion and the high pressure in the balloon.
In practice, however, the nanobubbles can survive for weeks, as was already observed more than twenty years ago. Nevertheless, scientists failed to find a conclusive explanation for this long lifetime. With the publication of an article in the scientific journal Physical Review E (Rapid Communication), prof. dr. ir. Detlef Lohse and prof. dr. Xuehua Zhang (who besides the UT is also affiliated with the RMIT University in Melbourne) finally provide an explanation for the phenomenon. And they do this with a complete analytical method with relatively simple mathematical formulas.
Angle of curvature
The reason that the bubbles survive for such a long period of time lies in the pinning of the three phase contact line. Thanks to the pinning, bubble shrinkage implies an increase of the radius of curvature and thus a smaller Laplace pressure. For stable bubbles the outflux originating from the Laplace pressure and the influx due to oversaturation balance. The result is a stable equilibrium.
The research not only provides an answer to a fundamental physical and chemical question, but also has all sorts of practical applications. The knowledge can, for example, be used to make catalytic reactions more efficient and for flotation processes, a purification technique that is used a lot in the extraction of minerals.
Within his Physics of Fluids (POF) Department at the University of Twente, Lohse has already been working on this topic for more than ten years. In this research, he works closely with prof. dr. ir. Harold Zandvliet from the Physics of Interfaces and Nanomaterials (PIN) department. The research is part of the MCEC Gravity Programme, within which the University of Utrecht, the Eindhoven University of Technology and the University of Twente work together on the development of efficient catalytic processes for different energy and material resources, such as fossil fuels, biomass and solar energy. NWO is financing this programme with 31.9 million euros.
drs Joost Bruysters | idw - Informationsdienst Wissenschaft
Researchers identify a protein that keeps metastatic breast cancer cells dormant
23.01.2018 | Institute for Research in Biomedicine (IRB Barcelona)
Opening the cavity floodgates
23.01.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau
Physicists have developed a technique based on optical microscopy that can be used to create images of atoms on the nanoscale. In particular, the new method allows the imaging of quantum dots in a semiconductor chip. Together with colleagues from the University of Bochum, scientists from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute reported the findings in the journal Nature Photonics.
Microscopes allow us to see structures that are otherwise invisible to the human eye. However, conventional optical microscopes cannot be used to image...
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
23.01.2018 | Earth Sciences
23.01.2018 | Life Sciences
23.01.2018 | Materials Sciences