Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Droplets Levitate on a Cushion of Blue Light


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:

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.

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:  

Contact Information
Jason Socrates Bardi

Jason Socrates Bardi | newswise

More articles from Physics and Astronomy:

nachricht Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)

nachricht Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

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: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>