Tag Archives: vibrations

A Moebius strip of moving energy (vibrations)

This research extends a theorem which posits that waves will adapt to slowly changing conditions and return to their original vibration to note that the waves can be manipulated to a new state. A July 25, 2016 news item on ScienceDaily makes the announcement,

Yale physicists have created something similar to a Moebius strip of moving energy between two vibrating objects, opening the door to novel forms of control over waves in acoustics, laser optics, and quantum mechanics.

The discovery also demonstrates that a century-old physics theorem offers much greater freedom than had long been believed. …

A July 25, 2016 Yale University news release (also on EurekAlert) by Jim Shelton, which originated the news item, expands on the theme,

Yale’s experiment is deceptively simple in concept. The researchers set up a pair of connected, vibrating springs and studied the acoustic waves that traveled between them as they manipulated the shape of the springs. Vibrations — as well as other types of energy waves — are able to move, or oscillate, at different frequencies. In this instance, the springs vibrate at frequencies that merge, similar to a Moebius strip that folds in on itself.

The precise spot where the vibrations merge is called an “exceptional point.”

“It’s like a guitar string,” said Jack Harris, a Yale associate professor of physics and applied physics, and the study’s principal investigator. “When you pluck it, it may vibrate in the horizontal plane or the vertical plane. As it vibrates, we turn the tuning peg in a way that reliably converts the horizontal motion into vertical motion, regardless of the details of how the peg is turned.”

Unlike a guitar, however, the experiment required an intricate laser system to precisely control the vibrations, and a cryogenic refrigeration chamber in which the vibrations could be isolated from any unwanted disturbance.

The Yale experiment is significant for two reasons, the researchers said. First, it suggests a very dependable way to control wave signals. Second, it demonstrates an important — and surprising — extension to a long-established theorem of physics, the adiabatic theorem.

The adiabatic theorem says that waves will readily adapt to changing conditions if those changes take place slowly. As a result, if the conditions are gradually returned to their initial configuration, any waves in the system should likewise return to their initial state of vibration. In the Yale experiment, this does not happen; in fact, the waves can be manipulated into a new state.

“This is a very robust and general way to control waves and vibrations that was predicted theoretically in the last decade, but which had never been demonstrated before,” Harris said. “We’ve only scratched the surface here.”

In the same edition of Nature, a team from the Vienna University of Technology also presented research on a system for wave control via exceptional points.

Here’s a link to and a citation for the paper,

Topological energy transfer in an optomechanical system with exceptional points by H. Xu, D. Mason, Luyao Jiang, & J. G. E. Harris. Nature (2016) doi:10.1038/nature18604 Published online 25 July 2016

This paper is behind a paywall.

How vibrations affect nanoscale materials

A March 9, 2016 news item on ScienceDaily announces work concerning atomic vibrations,

All materials are made up of atoms, which vibrate. These vibrations, or ‘phonons’, are responsible, for example, for how electric charge and heat is transported in materials. Vibrations of metals, semiconductors, and insulators in are well studied; however, now materials are being nanosized to bring better performance to applications such as displays, sensors, batteries, and catalytic membranes. What happens to vibrations when a material is nanosized has until now not been understood.

A March 9, 2016 ETH Zurich press release (also on EurekAlert), which originated the news item, describes the world of vibration at the nanoscale and the potential impact this new information could have,

Soft Surfaces Vibrate Strongly

In a recent publication in Nature, ETH Professor Vanessa Wood and her colleagues explain what happens to atomic vibrations when materials are nanosized and how this knowledge can be used to systematically engineer nanomaterials for different applications.

The paper shows that when materials are made smaller than about 10 to 20 nanometers – that is, 5,000 times thinner than a human air – the vibrations of the outermost atomic layers on surface of the nanoparticle are large and play an important role in how this material behaves.

“For some applications, like catalysis, thermoelectrics, or superconductivity, these large vibrations may be good, but for other applications like LEDs or solar cells, these vibrations are undesirable,” explains Wood.

Indeed, the paper explains why nanoparticle-based solar cells have until now not met their full promise.  The researchers showed using both experiment and theory that surface vibrations interact with electrons to reduce the photocurrent in solar cells.

“Now that we have proven that surface vibrations are important, we can systematically design materials to suppress or enhance these vibrations,” say Wood.

Improving Solar Cells

Wood’s research group has worked for a long time on a particular type of nanomaterial – colloidal nanocrystals – semiconductors with a diameter of 2 to 10 nanometers.  These materials are interesting because their optical and electrical properties are dependent on their size, which can be easily changed during their synthesis.

These materials are now used commercially as red- and green-light emitters in LED-based TVs and are being explored as possible materials for low cost, solution-processed solar cells.  Researchers have noticed that placing certain atoms around the surface of the nanocrystal can improve the performance of solar cells. The reason why this worked had not been understood.  The work published in the Nature paper now gives the answer:  a hard shell of atoms can suppress the vibrations and their interaction with electrons.  This means a higher photocurrent and a higher efficiency solar cell.

Big Science to Study the Nanoscale

Experiments were conducted in Professor Wood’s labs at ETH Zurich and at the Swiss Spallation Neutron Source at the Paul Scherrer Institute. By observing how neutrons scatter off atoms in a material, it is possible to quantify how atoms in a material vibrate. To understand the neutron measurements, simulations of the atomic vibrations were run at the Swiss National Supercomputing Center (CSCS) in Lugano. Wood says, “without access to these large facilities, this work would not have been possible. We are incredibly fortunate here in Switzerland to have these world class facilities.”

The researchers have made available an image illustrating their work,

Vibrations of atoms in materials, the "phonons", are responsible for how electric charge and heat is transported in materials (Graphics: Deniz Bozyigit / ETH Zurich)

Vibrations of atoms in materials, the “phonons”, are responsible for how electric charge and heat is transported in materials (Graphics: Deniz Bozyigit / ETH Zurich)

Here’s a link to and a citation for the paper,

Soft surfaces of nanomaterials enable strong phonon interactions by Deniz Bozyigit, Nuri Yazdani, Maksym Yarema, Olesya Yarema, Weyde Matteo Mario Lin, Sebastian Volk, Kantawong Vuttivorakulchai, Mathieu Luisier, Fanni Juranyi, & Vanessa Wood. Nature (2016)  doi:10.1038/nature16977 Published online 09 March 2016

This paper is behind a paywall.

A watch that conducts sound through your body and into your ear

Apparently, you all you have to do is tap your ear to access your telephone calls. A Jan. 8, 2016 article by Mark Wilson for Fast Company describes the technology and the experience of using Samsung’s TipTalk device,

It’s not so helpful to see a call on your smartwatch when you have to pull our your phone to take it anyway. And therein lies the problem with products like the Apple Watch: They’re often not a replacement for your phone, but an intermediary to inevitably using it.

But at this year’s Consumer Electronics Show [held in Las Vegas (Nevada, US) annually (Jan. 6 – 9, 2016)], Samsung’s secret R&D lab … showed off a promising concept to fix one of the biggest problems with smartwatches. Called TipTalk, it’s technology that can send sound from your smartwatch through your arm so when you touch your finger to your ear, you can hear a call or a voicemail—no headphones required.

Engineering breakthroughs like these can be easy to dismiss as a gimmick rather than revolutionary UX [user experience], but I like TipTalk for a few reasons. First, it maps hearing UI [user interface] into a gesture that we already might use to hear to something better … . Second, it could be practical in real world use. You see a new voicemail on your watch, and without even a button press, you listen—but crucially, you still opt-in to hear the message rather than just have it play. And third, the gesture conveys to people around you that you’re occupied.

Ulrich Rozier in his Jan. 8, 2016 article for frandroid.com also raves albeit, in French,

Samsung a développé un bracelet que l’on peut utiliser sur n’importe quelle montre.

Ce bracelet vibre lorsque l’on reçoit un appel… il est ainsi possible de décrocher. Il faut ensuite positionner son doigt au niveau du pavillon de l’oreille. C’est là que la magie opère. On se retrouve à entendre des sons. Contrairement à ce que je pensais, le son ne se transmet pas par conduction osseuse, mais grâce à des vibrations envoyées à partir de votre poignet à travers votre corps. Vous pouvez l’utiliser pour prendre des appels ou pour lire vos SMS et autres messages. Et ça fonctionne.

Here’s my very rough translation,

Samsung has developed a bracelet that can worn under any watch’s band strap.

It’s the ‘bracelet’ that vibrates when you get a phone call. If you want to answer the call, reach up and tap your ear. That’s when the magic happens and sound is transmitted to your ear. Not through your bones as I thought but with vibrations transmitted by your wrist through your body. This way you can answer your calls or read SMS and other messages [?]. It works

I get sound vibration being transmitted to your ear but I don’t understand how you’d be able to read SMS or other messages.

Feel the vibe on Nanophonics Day

Officially, Nanophonics Day was held on May 26, 2014 but it’s never too late to appreciate good vibrations. Here’s more about the ‘day’ and nanophonics from a May 27, 2014 news item on Azonano (Note: A link has been removed),

The Nanophononics Day, collocated with the European Materials Research Society Spring Meeting (Lille, 26-30 May), aims to raise awareness about this emergent research area and the EUPHONON Project. ICREA Prof Dr Clivia Sotomayor, Group Leader at ICN2, coordinates this initiative.

A phonon is a collective excitation of atoms or molecules, a vibration of matter which plays a major role in physical properties of solids and liquids. Nanophononics is the science and engineering of these vibrations at the nanometre scale. Applications of the knowledge generated in the field might include novel devices aiming to decrease the power consumption for a low-power information society. It also includes phonon lasers and phenomena involving ultra-fast acoustic processes, or exceeding the limits of mass and pressure detections in membranes which might have an impact in safety and technology standards. Nanophononics links classical and quantum physics and translates this knowledge into everyday applications.

A May 26, 2014 Institut Català de Nanociència i Nanotecnologia (ICN2) news release, which originated the news item, provides more details about European research into nanophonics,

The EUPHONON project aims to amalgamate the activities on phonon science and technology in Europe to establish a strong community in this emerging research field. It started in November 2013, coordinated by Prof. Sebastian Volz from CNRS – École Central Paris. ICREA Prof Dr Clivia M Sotomayor Torres, Phononic and Photonic Nanostructures (P2N) Group Leader at the Institut Català de Nanociència i Nanotecnologia (ICN2), is among the 7 members of the consortium. She is the coordinator of the Nanophononics Day, intended to raise awareness about this emergent research area and the EUPHONON Project.

The Nanophononics Day is celebrated in May 26th 2014, collocated with Symposium D of the European Materials Research Society (E-MRS) Spring Meeting 2014 in Lille, entitled “Phonons and Fluctuation in Low Dimensional Structures” and with ICREA Prof Dr Clivia M Sotomayor Torres again among its organizers. It is probably the largest nanophononic event in Europe and a perfect context for a lively discussion about the most recent theoretical and experimental findings.

The Nanophononics Day includes conferences by leading scientists about recent breakthroughs in nano-scale thermal transport and how the recent achievements constitute solid base for nanophononics. Prof Gang Chen (MIT, USA) and Prof Olivier Bourgeois (CNRS Inst. Neel) will cover phonons in solid materials while phonons in biological matter will be addressed by Prof Thomas Dehoux (University of Bordeaux). Experimental methods using scanning probes will be illustrated by Prof Oleg Kolosov (Lancaster University) and Prof Severine Gomez (University of Lyon).

I wish you a belated Happy Nanophonics Day!