Tag Archives: acoustic waves

Using acoustic waves to move fluids at the nanoscale

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A Nov. 14, 2016 news item on ScienceDaily describes research that could lead to applications useful for ‘lab-on-a-chip’ operations,

A team of mechanical engineers at the University of California San Diego [UCSD] has successfully used acoustic waves to move fluids through small channels at the nanoscale. The breakthrough is a first step toward the manufacturing of small, portable devices that could be used for drug discovery and microrobotics applications. The devices could be integrated in a lab on a chip to sort cells, move liquids, manipulate particles and sense other biological components. For example, it could be used to filter a wide range of particles, such as bacteria, to conduct rapid diagnosis.

A Nov. 14, 2016 UCSD news release (also on EurrekAlert), which originated the news item, provides more information,

The researchers detail their findings in the Nov. 14 issue of Advanced Functional Materials. This is the first time that surface acoustic waves have been used at the nanoscale.

The field of nanofluidics has long struggled with moving fluids within channels that are 1000 times smaller than the width of a hair, said James Friend, a professor and materials science expert at the Jacobs School of Engineering at UC San Diego. Current methods require bulky and expensive equipment as well as high temperatures. Moving fluid out of a channel that’s just a few nanometers high requires pressures of 1 megaPascal, or the equivalent of 10 atmospheres.

Researchers led by Friend had tried to use acoustic waves to move the fluids along at the nano scale for several years. They also wanted to do this with a device that could be manufactured at room temperature.

After a year of experimenting, post-doctoral researcher Morteza Miansari, now at Stanford, was able to build a device made of lithium niobate with nanoscale channels where fluids can be moved by surface acoustic waves. This was made possible by a new method Miansari developed to bond the material to itself at room temperature.  The fabrication method can be easily scaled up, which would lower manufacturing costs. Building one device would cost $1000 but building 100,000 would drive the price down to $1 each.

The device is compatible with biological materials, cells and molecules.

Researchers used acoustic waves with a frequency of 20 megaHertz to manipulate fluids, droplets and particles in nanoslits that are 50 to 250 nanometers tall. To fill the channels, researchers applied the acoustic waves in the same direction as the fluid moving into the channels. To drain the channels, the sound waves were applied in the opposite direction.

By changing the height of the channels, the device could be used to filter a wide range of particles, down to large biomolecules such as siRNA, which would not fit in the slits. Essentially, the acoustic waves would drive fluids containing the particles into these channels. But while the fluid would go through, the particles would be left behind and form a dry mass. This could be used for rapid diagnosis in the field.

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

Acoustic Nanofluidics via Room-Temperature Lithium Niobate Bonding: A Platform for Actuation and Manipulation of Nanoconfined Fluids and Particles by Morteza Miansari and James R. Friend. Advanced Functional Materials DOI: 10.1002/adfm.201602425 Version of Record online: 20 SEP 2016
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

They do have an animation sequence illustrating the work but it could be considered suggestive and is, weirdly, silent,

 

 

Move objects by playing a melody

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At this point, moving objects by playing a melody is a laboratory experiment but who knows, perhaps one day you’ll be able to sing your front door open. A Sept. 9, 2016 news item on ScienceDaily announces the research on acoustic waves,

Researchers of Aalto University have made a breakthrough in controlling the motion of multiple objects on a vibrating plate with a single acoustic source. By playing carefully constructed melodies, the scientists can simultaneously and independently move multiple objects on the plate towards desired targets. This has enabled scientists, for instance, writing words consisting of separate letters with loose metal pieces on the plate by playing a melody.

A Sept. 9, 2016 Aalto University press release (also on EurekAlert), which originated the news item, describes the research in more detail,

Already in 1878, the first studies of sand moving on a vibrating plate were done by Ernst Chladni, known as the father of acoustics. Chladni discovered that when a plate is vibrating at a frequency, objects move towards a few positions, called the nodal lines, specific to that frequency. Since then, the prevailing view has been that the particle motion is random on the plate before they reached the nodal line. “We have shown that the motion is also predictable away from the nodal lines. Now that the object does not have to be at a nodal line, we have much more freedom in controlling its motion and have achieved independent control of up to six objects simultaneously using just one single actuator. We are very excited about the results, because this probably is a new world record of how many independent motions can be controlled by a single acoustic actuator,” says Professor Quan Zhou.

The objects to be controlled have been placed on top of a manipulation plate, and imaged by a tracking camera. Based on the detected positions, the computer goes through a list of music notes to find a note that is most likely to move the objects towards the desired directions. After playing the note, the new positions of the objects are detected, and the control cycle is restarted. This cycle is repeated until the objects have reached their desired target locations. The notes played during the control cycles form a sequence, a bit like music.

The new method has been applied to manipulate a wide range of miniature objects including electronic components, water droplets, plant seeds, candy balls and metal parts. “Some of the practical applications we foresee include conveying and sorting microelectronic chips, delivering drug-loaded particles for pharmaceutical applications or handling small liquid volumes for lab on chips,” says Zhou. “Also, the basic idea should be transferrable to other kinds of systems with vibration phenomena. For example, it should be possible to use waves and ripples to control floating objects in a pond using our technique.”

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

Controlling the motion of multiple objects on a Chladni plate by Quan Zhou, Veikko Sariola, Kourosh Latifi, Ville Liimatainen. Nature Communications 7, Article number: 12764 doi:10.1038/ncomms12764 Published 09 September 2016

This article is open access.

A Moebius strip of moving energy (vibrations)

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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.

Swallow your technology and wear it inside (wearable tech: 2 of 3)

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While there are a number of wearable and fashionable pieces of technology that monitor heart rate and breathing, they are all worn on the outside of your body. Researchers are working on an alternative that can be swallowed and will monitor vital signs from within the gastrointestinal tract. I believe this is a prototype of the device,

This ingestible electronic device invented at MIT can measure heart rate and respiratory rate from inside the gastrointestinal tract. Courtesy: MIT

This ingestible electronic device invented at MIT can measure heart rate and respiratory rate from inside the gastrointestinal tract. Image: Albert Swiston/MIT Lincoln Laboratory Courtesy: MIT

From a Nov. 18, 2015 news item on phys.org,

This type of sensor could make it easier to assess trauma patients, monitor soldiers in battle, perform long-term evaluation of patients with chronic illnesses, or improve training for professional and amateur athletes, the researchers say.

The new sensor calculates heart and breathing rates from the distinctive sound waves produced by the beating of the heart and the inhalation and exhalation of the lungs.

“Through characterization of the acoustic wave, recorded from different parts of the GI tract, we found that we could measure both heart rate and respiratory rate with good accuracy,” says Giovanni Traverso, a research affiliate at MIT’s Koch Institute for Integrative Cancer Research, a gastroenterologist at Massachusetts General Hospital, and one of the lead authors of a paper describing the device in the Nov. 18 issue of the journal PLOS One.

A Nov. 18, 2015 Massachusetts Institute of Technology (MIT) news release by Anne Trafton, which originated the news item, further explains the research,

Doctors currently measure vital signs such as heart and respiratory rate using techniques including electrocardiograms (ECG) and pulse oximetry, which require contact with the patient’s skin. These vital signs can also be measured with wearable monitors, but those are often uncomfortable to wear.

Inspired by existing ingestible devices that can measure body temperature, and others that take internal digestive-tract images, the researchers set out to design a sensor that would measure heart and respiratory rate, as well as temperature, from inside the digestive tract.

The simplest way to achieve this, they decided, would be to listen to the body using a small microphone. Listening to the sounds of the chest is one of the oldest medical diagnostic techniques, practiced by Hippocrates in ancient Greece. Since the 1800s, doctors have used stethoscopes to listen to these sounds.

The researchers essentially created “an extremely tiny stethoscope that you can swallow,” Swiston says. “Using the same sensor, we can collect both your heart sounds and your lung sounds. That’s one of the advantages of our approach — we can use one sensor to get two pieces of information.”

To translate these acoustic data into heart and breathing rates, the researchers had to devise signal processing systems that distinguish the sounds produced by the heart and lungs from each other, as well as from background noise produced by the digestive tract and other parts of the body.

The entire sensor is about the size of a multivitamin pill and consists of a tiny microphone packaged in a silicone capsule, along with electronics that process the sound and wirelessly send radio signals to an external receiver, with a range of about 3 meters.

In tests along the GI tract of pigs, the researchers found that the device could accurately pick up heart rate and respiratory rate, even when conditions such as the amount of food being digested were varied.

“The authors introduce some interesting and radically different approaches to wearable physiological status monitors, in which the devices are not worn on the skin or on clothing, but instead reside, in a transient fashion, inside the gastrointestinal tract. The resulting capabilities provide a powerful complement to those found in wearable technologies as traditionally conceived,” says John Rogers, a professor of materials science and engineering at the University of Illinois who was not part of the research team.

Better diagnosis

The researchers expect that the device would remain in the digestive tract for only a day or two, so for longer-term monitoring, patients would swallow new capsules as needed.

For the military, this kind of ingestible device could be useful for monitoring soldiers for fatigue, dehydration, tachycardia, or shock, the researchers say. When combined with a temperature sensor, it could also detect hypothermia, hyperthermia, or fever from infections.

In the future, the researchers plan to design sensors that could diagnose heart conditions such as abnormal heart rhythms (arrhythmias), or breathing problems including emphysema or asthma. Currently doctors require patients to wear a harness (Holter) monitor for up to a week to detect such problems, but these often fail to produce a diagnosis because patients are uncomfortable wearing them 24 hours a day.

“If you could ingest a device that would listen for those pathological sounds, rather than wearing an electrical monitor, that would improve patient compliance,” Swiston says.

The researchers also hope to create sensors that would not only diagnose a problem but also deliver a drug to treat it.

“We hope that one day we’re able to detect certain molecules or a pathogen and then deliver an antibiotic, for example,” Traverso says. “This development provides the foundation for that kind of system down the line.”

MIT has provided a video with two of the researchers describing their work and and plans for its future development,

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

Physiologic Status Monitoring via the Gastrointestinal Tract by G. Traverso, G. Ciccarelli, S. Schwartz, T. Hughes, T. Boettcher, R. Barman, R. Langer, & A. Swiston. PLOS DOI: 10.1371/journal.pone.0141666 Published: November 18, 2015

This paper is open access.

Note added Nov. 25, 2015 at 1625 hours PDT: US National Public Radio (NPR) has a story on this research. You can find Nov. 23, 2015 podcast (about six minutes) and a series of textual excerpts featuring Albert Swiston, biomaterials scientist at MIT, and Stephen Shankland, senior writer for CNET covering digital technology, from the podcast here.