Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Droplets Levitate on a Cushion of Blue Light

13.08.2015

Applying more than 50 volts across a droplet of weak hydrochloric acid causes the drop to rise into the air above a glowing plasma layer

Researchers in France have discovered a new way to levitate liquid droplets, which surprisingly also creates a mini light show, with the droplet sparking as it floats above a faint blue glowing gap.


Cedric Poulain, et al / CEA

A blue glow emanates from beneath a levitating droplet of weak hydrochloric acid. The glow comes from a plasma created when researchers applied above 50 volts of electricity across the droplet.

Described this week in the journal Applied Physics Letters, from AIP Publishing, the work may offer an inexpensive new way to generate a freely movable microplasma, as well as yield insights into fundamental physics questions.

The floating effect is similar to Leidenfrost levitation -- in which droplets dance on a hot vapor cushion. But by creating the vapor with a strong jolt of electricity instead of heat, the researchers found they could ionize the gas into a plasma that glowed a soft blue light.

"This method is probably an easy and original way to make a plasma," said Cedric Poulain, a physicist at the French Alternative Energies and Atomic Energy Commission. Poulain speculates that the deformability of a liquid drop would let the researchers rig up a device to move the plasma along a surface, but he admits that such applications were far from his and his colleagues' minds when they first conceived the experiment.

At first, the researchers wanted to explore the limits of the analogy between the boiling phenomenon and water electrolysis, which is the breakup of water into hydrogen and oxygen gases by an electric current.

As an example of boiling behavior, Poulain described the case of a liquid droplet at the surface of a hot pan. If the pan temperature is just above 100 degrees Celsius, the drop spreads and water vapor bubbles grow at the pan surface. However, if the pan is very hot (more than 280 degrees Celsius), a cushion of vapor is formed between the drop and the pan, levitating the drop and preventing contact between the liquid water and the pan, a phenomenon called the Leidenfrost effect. "This is a classical ‘grandmother’ trick to test the temperature of a pan," Poulain said.

The team wondered if a similar transition exists in the case of water electrolysis. The analogy interested the authors, because they study an event called "boiling crisis" in nuclear power plant steam generators. If the core of a nuclear reactor gets too hot, bubbles in the cooling water can suddenly coalesce to form a vapor film that limits further heat transfer and leads to a dangerous increase in temperature.

A Cushion of Vapor from a Jolt of Electricity

In their lab, Poulain and his colleagues devised a set-up to run electricity through conductive droplets and film the droplets' behavior at high speed. They suspended a small drop of weak hydrochloric acid, which conducts electricity, above a metal plate and applied a voltage across the drop. When the drop touched the plate, electricity began to flow, and the water in the hydrochloric acid solution started to break down into hydrogen and oxygen gas.

Above 50 volts, the bottom of the droplet started sparking. It levitated, rising over the surface of the plate, and a faint blue glow emanated from the gap.

At first the researchers believed that the drop might be resting on a cushion of hydrogen gas from the breakup of water, but further analysis revealed that the gaseous cushion was in fact mostly water vaporized by energy from the electric current.

The blue light emission was unexpected and probably the most exciting feature of the experiment, the team said. Although fifty volts is a relatively low voltage, Poulain explained that the tiny gap between the droplet and the metal plate is what gives rise to the very high electric field necessary to generate a long-term and dense plasma with little energy.

Exploring the Blue Light

The researchers next plan to analyze the composition of the plasma layer. They say it appears to be a superposition of two types of plasma that is not well understood. They will also study the fast dynamics at the bottom of the drop just as the sparks begin to fly, which should yield additional insights into the plasma.

Although plasma dynamics may seem far removed from the problem of film boiling in nuclear reactors, Poulain is happy about the path the curiosity-driven research has taken the team.

"It's very exciting," he said of the team's foray into plasma levitation.

###

The article, "The plasma levitation of droplets," is authored by Cedric Poulain, Antoine Dugue, Antoine Durieux, Nader Sadeghi, and Jerome Duplat. It will be published in the journal Applied Physics Letters on August 11, 2015 (DOI: 10.1063/1.4926964). After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/apl/107/6/10.1063/1.4926964

The authors of this paper are affiliated with the French Alternative Energies and Atomic Energy Commission (CEA), Ecole Polytechnique, and the University of Grenoble Alpes.

ABOUT THE JOURNAL
Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology. See: http://apl.aip.org  

Contact Information
Jason Socrates Bardi
jbardi@aip.org
240-535-4954
@jasonbardi

Jason Socrates Bardi | newswise

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Northern oceans pumped CO2 into the atmosphere

27.03.2017 | Earth Sciences

Fingerprint' technique spots frog populations at risk from pollution

27.03.2017 | Life Sciences

Big data approach to predict protein structure

27.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>