Fantastic phonons: Blocking sound, channeling heat with 'unprecedented precision'

Nov 13, 2013
Martin Maldovan, of the Georgia Institute of Technology, has published a review article on phononics in Nature. Credit: Credit: Rob Felt.

Imagine living on a bustling city block, but free from the noise of car horns and people on the street. The emerging field of phononics could one day make this a reality.

The phonon, like the photon or electron, is a physical particle that travels like waves, representing mechanical vibration. Phonons transmit everyday sound and heat. Recent progress in phononics has led to the development of new ideas and devices that are using phononic properties to control sound and heat, according to a new review in Nature.

One application that has scientists buzzing is the possibility of controlling by designing and fabricating cloaking shells to guide around a certain object – an entire building, perhaps – so that whatever is inside the shell is invisible to the sound waves.

The future possibilities for phonons might also solve the biggest challenges in energy consumption and buildings today. Understanding and controlling the phononic properties of materials could lead to novel technologies to thermally insulate buildings, reduce environmental noise, transform into electricity and develop earthquake protection, all by developing new materials to manipulate sound and heat. These ideas are all possible in theory, but to make them a reality, phononics will have to inspire the same level of scientific innovation as electronics, and today that's not the case.

"People know about electrons because of computers, and because of cell phones, but not so much about phonons," said Martin Maldovan, a research scientist in the School of Chemical and Biomolecular Engineering at the Georgia Institute of Technology.

Maldovan's review article appeared online Nov. 13 in the journal Nature. In the article he blends eight different subjects in the field of phononics, describing advances in sonic and thermal diodes, optomechanical crystals, acoustic and thermal cloaking, hypersonic phononic crystals, thermoelectrics and thermocrystals.

These technologies "herald the next technological revolution in phononics," he said. All of these areas share a common theme: manipulating mechanical vibrations, but at different frequences.

The hottest fields in phononics, Maldovan said, is the development of acoustic and thermal metamaterials. These materials are capable of cloaking sound waves and thermal flows. The phononics approach to cloaking is based on electromagnetic cloaking materials that are already in use for light.

Maldovan, formerly a research scientist at the Massachusetts Institute of Technology, also conducts phononics research of his own. This past summer, Maldovan published an article in the journal Physical Review Letters, describing an invention for controlling the conduction of heat through solid objects.

Known as thermocrystals, this new area of phononics research seeks to manage in a similar manner as sound and , by channeling the flow of heat at certain frequencies. The technology could lead to devices that convert heat into energy, or the thermal equivalent of diodes, which could help data centers solve the problem of massive heat generated by their servers.

"The field of Phononics is relatively new, and when you have something new you don't know what you will find," Maldovan said. "You're always thinking 'what can I do with that?'"

Explore further: Designing an acoustic diode

More information: M Maldovan. "Sound and heat revolutions in phononics," Nature, 2013. DOI: 10.1038/nature12608

Related Stories

Designing an acoustic diode

Nov 01, 2013

Most people know about ultrasound through its role in prenatal imaging: those grainy, grey outlines of junior constructed from reflected sound waves. A new technology called an "acoustic diode," envisioned ...

Scientists Propose Thermal Memory to Store Data

Jan 07, 2009

Most computers today store memory electronically, by maintaining a certain voltage. In contrast, a new kind of memory that stores data thermally, by maintaining temperature, is being investigated by researchers Lei Wang of ...

Acoustic cloaking device echoes advances in optical cloaking

Aug 15, 2011

Optical cloaking devices that enable light to gracefully slip around a solid object were once strictly in the realm of science fiction. Today they have emerged as an exciting area of study, at least on microscopic scales. ...

Recommended for you

Uncovering the forbidden side of molecules

Sep 21, 2014

Researchers at the University of Basel in Switzerland have succeeded in observing the "forbidden" infrared spectrum of a charged molecule for the first time. These extremely weak spectra offer perspectives ...

How Paramecium protozoa claw their way to the top

Sep 19, 2014

The ability to swim upwards – towards the sun and food supplies – is vital for many aquatic microorganisms. Exactly how they are able to differentiate between above and below in often murky waters is ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

grondilu
not rated yet Nov 13, 2013
I wonder if phonics could be used to cool electronic chips, one day.
bearly
3 / 5 (1) Nov 14, 2013
Is it possible that by directing heat/sound around an object that this could become part of a "force field" ?