Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New metamaterial manipulates sound to improve acoustic imaging

17.12.2015

Researchers from North Carolina State University and Duke University have developed a metamaterial made of paper and aluminum that can manipulate acoustic waves to more than double the resolution of acoustic imaging, focus acoustic waves, and control the angles at which sound passes through the metamaterial. Acoustic imaging tools are used in both medical diagnostics and in testing the structural integrity of everything from airplanes to bridges.

"This metamaterial is something that we've known is theoretically possible, but no one had actually made it before," says Yun Jing, an assistant professor of mechanical and aerospace engineering at NC State and corresponding author of a paper describing the work.


The metamaterial, shown here, is made of paper and aluminum -- but its structure allows it to manipulate acoustic waves to more than double the resolution of acoustic imaging, focus acoustic waves, and control the angles at which sound passes through the metamaterial. Acoustic imaging tools are used in both medical diagnostics and in testing the structural integrity of everything from airplanes to bridges.

Credit: Chen Shen, North Carolina State University

Metamaterials are simply materials that have been engineered to exhibit properties that are not found in nature. In this case, the structural design of the metamaterial gives it qualities that make it a "hyperbolic" metamaterial. This means that it interacts with acoustic waves in two different ways.

From one direction, the metamaterial exhibits a positive density and interacts with acoustic waves normally - just like air. But from a perpendicular direction, the metamaterial exhibits a negative density in terms of how it interacts with sound. This effectively makes acoustic waves bend at angles that are the exact opposite of what basic physics would tell you to expect.

The practical effect of this is that the metamaterial has some very useful applications.

For one thing, the metamaterial can be used to improve acoustic imaging. Traditionally, acoustic imaging could not achieve image resolution that was smaller than half of a sound's wavelength. For example, an acoustic wave of 100 kilohertz (kHz), traveling through air, has a wavelength of 3.4 millimeters (mm) - so it couldn't achieve image resolution smaller than 1.7 mm.

"But our metamaterial improves on that," says Chen Shen, a Ph.D. student at NC State and lead author of the paper. "By placing the metamaterial between the imaging device and the object being imaged, we were able to more than double the resolution of the acoustic imaging - from one-half the sound's wavelength to greater than one-fifth."

The metamaterial can also focus acoustic waves, which makes it a flexible tool.

"Medical personnel and structural engineers sometimes need to focus sound for imaging or therapeutic purposes," Jing says. "Our metamaterial can do that, or it can be used to improve resolution. There are few tools out there that can do both."

Lastly, the metamaterial gives researchers more control over the angle at which acoustic waves can pass through it.

"For example, the metamaterial could be designed to block sound from most angles, leaving only a small opening for sound to pass through, which might be useful for microphones," Shen says. "Or you could leave it wide open - it's extremely flexible."

Right now, the prototype metamaterial is approximately 30 centimeters square, and is effective for sounds between 1 and 2.5 kHz.

"Our next steps are to make the structure much smaller, and to make it operate at higher frequencies," Jing says.

###

The paper, "Broadband Acoustic Hyperbolic Metamaterial," was published online Dec. 16 in the journal Physical Review Letters. The paper was co-authored by Ni Sui of NC State and Yangbo Xie, Wenqi Wang and Steven Cummer of Duke.

Media Contact

Matt Shipman
matt_shipman@ncsu.edu
919-515-6386

 @NCStateNews

http://www.ncsu.edu 

Matt Shipman | EurekAlert!

More articles from Materials Sciences:

nachricht Decoding cement's shape promises greener concrete
08.12.2016 | Rice University

nachricht Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D
08.12.2016 | DOE/Brookhaven National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

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

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>