Sound waves power new advances in drug delivery and smart materials

Sound waves power new advances in drug delivery and smart materials
The patented ‘Respite’ nebuliser uses high-frequency sound waves to precisely deliver drugs to the lungs. Credit: RMIT University

Researchers have revealed how high-frequency sound waves can be used to build new materials, make smart nanoparticles and even deliver drugs to the lungs for painless, needle-free vaccinations.

While sound waves have been part of science and medicine for decades—ultrasound was first used for clinical imaging in 1942 and for driving chemical reactions in the 1980s—the technologies have always relied on low frequencies.

Now researchers at RMIT University in Melbourne, Australia, have shown how high frequency sound waves could revolutionize the field of ultrasound-driven chemistry.

A new review published in Advanced Science reveals the bizarre effects of these sound waves on materials and cells, such as molecules that seem to spontaneously order themselves after being hit with the sonic equivalent of a semi-trailer.

The researchers also detail various exciting applications of their pioneering work, including:

  • Drug delivery to the lungs—patented nebulisation technology that could deliver life-saving drugs and vaccines by inhalation, rather than through injections
  • Drug-protecting nanoparticles—encapsulating drugs in special nano-coatings to protect them from deterioration, control their release over time and ensure they precisely target the right places in the body like tumors or infections
  • Breakthrough smart materials—sustainable production of super-porous nanomaterials that can be used to store, separate, release, protect almost anything
  • Nano-manufacturing 2-D materials—precise, cost-effective and fast exfoliation of atomically-thin quantum dots and nanosheets

Lead researcher Distinguished Professor Leslie Yeo and his team have spent over a decade researching the interaction of sound waves at frequencies above 10 MHz with different materials.

But Yeo says they are only now starting to understand the range of strange phenomena they often observe in the lab.

“When we couple high-frequency sound waves into fluids, materials and cells, the effects are extraordinary,” he says.

“We’ve harnessed the power of these sound waves to develop innovative biomedical technologies and to synthesize advanced materials.

“But our discoveries have also changed our fundamental understanding of ultrasound-driven chemistry—and revealed how little we really know.

“Trying to explain the science of what we see and then applying that to solve practical problems is a big and exciting challenge.”

Sonic waves: How to power chemistry with sound

The RMIT research team, which includes Dr. Amgad Rezk, Dr. Heba Ahmed and Dr. Shwathy Ramesan, generates high-frequency sound waves on a microchip to precisely manipulate fluids or materials.

Sound waves power new advances in drug delivery and smart materials
An acoustically-created MOF, with the microchip that produced the high-frequency sound waves used in the process. Credit: RMIT University

Ultrasound has long been used at low frequencies—around 10 kHz to 3 MHz—to drive chemical reactions, a field known as “sonochemistry”.

At these low frequencies, sonochemical reactions are driven by the violent implosion of air bubbles.

This process, known as cavitation, results in huge pressures and ultra-high temperatures—like a tiny and extremely localized pressure cooker.

But it turns out that if you up the frequency, these reactions change completely.

When high frequency sound waves were transmitted into various materials and

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LIGO and Virgo reveal a huge collection of gravitational waves

Earth is awash in gravitational waves.

Over a six-month period, scientists captured a bounty of 39 sets of gravitational waves. The waves, which stretch and squeeze the fabric of spacetime, were caused by violent events such as the melding of two black holes into one.

The haul was reported by scientists with the LIGO and Virgo experiments in several studies posted October 28 on a collaboration website and at The addition brings the tally of known gravitational wave events to 50.

The bevy of data, which includes sightings from April to October 2019, suggests that scientists’ gravitational wave–spotting skills have leveled up. Before this round of searching, only 11 events had been detected in the years since the effort began in 2015. Improvements to the detectors — two that make up the Advanced Laser Interferometer Gravitational-Wave Observatory, or LIGO, in the United States, and another, Virgo, in Italy — have dramatically boosted the rate of gravitational wave sightings.

While colliding black holes produced most of the ripples, a few collisions seem to have involved neutron stars, ultradense nuggets of matter left behind when stars explode.

Some of the events added to the gravitational wave register had been previously reported individually, including the biggest black hole collision spotted so far (SN: 9/2/20) and a collision between a black hole and an object that couldn’t be identified as either a neutron star or black hole (SN: 6/23/20).

Gravitational waves are produced when two massive objects, such as black holes, spiral around one another and merge. These visualizations, which are based on computer simulations, show these merging objects for 38 of the 50 known gravitational wave events.

What’s more, some of the coalescing black holes seem to be very large and spinning rapidly, says astrophysicist Richard O’Shaughnessy of the Rochester Institute of Technology in New York, a member of the LIGO collaboration. That’s something “really compelling in the data now that we hadn’t seen before,” he says. Such information might help reveal the processes by which black holes get partnered up before they collide (SN: 6/19/16).

Scientists also used the smorgasbord of smashups to further check Albert Einstein’s theory of gravity, general relativity, which predicts the existence of gravitational waves. When tested with the new data — surprise, surprise — Einstein came up a winner.

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Weak equivalence principle violated in gravitational waves

Credit: Pixabay/CC0 Public Domain

The Weak equivalence principle (WEP) is a key aspect of classical physics. It states that when particles are in freefall, the trajectories they follow are entirely independent of their masses. However, it is not yet clear whether this property also applies within the more complex field of quantum mechanics. In new research published in EPJ C, James Quach at the University of Adelaide, Australia, proves theoretically that the WEP can be violated by quantum particles in gravitational waves—the ripples in spacetime caused by colossal events such as merging black holes.

As well as resolving a long-standing debate in quantum theory, Quach’s findings could lead to the development of advanced new materials, including fluids with infinite conductivity and zero viscosity. These could be used as advanced gravitational wave detectors and may even lead to devices which can mirror gravitational waves and harvest their energy. Quach based his approach around a principle named ‘Fisher information’—a way of measuring how much information an observable random variable carries about a particular unknown parameter. Here, the random variable describes the position of a quantum particle in a gravitational field, while the unknown parameter is its mass. If the WEP were obeyed, the Fisher information should be zero in this case.

Through his calculations, Quach rewrote an equation describing the WEP for freely falling quantum particles, to incorporate their Fisher information. He showed that while these particles obey the WEP in static gravitational fields, their trajectories can indeed give away information about their mass when they pass through gravitational waves. For the first time, the calculation precisely characterizes how the WEP can be violated by quantum particles, and provides key insights for future studies searching for the violation through real experiments.

How Einstein’s equivalence principle extends to the quantum world

More information:
James Q. Quach, Fisher information and the weak equivalence principle of a quantum particle in a gravitational wave, The European Physical Journal C (2020). DOI: 10.1140/epjc/s10052-020-08530-6

Weak equivalence principle violated in gravitational waves (2020, October 28)
retrieved 28 October 2020

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Two new tropical waves forecast to emerge

Tropical activity is expected to kick up in the Atlantic basin over the weekend and into next week, forecasters said.

The National Hurricane Center is watching for two disturbances to form. Each has been given a 20% chance of development in the next five days.

The first is expected to form this weekend several hundred miles southeast of Bermuda and is likely to travel west next week, on a path midway between Bermuda and the Lesser Antilles.

It is forecast to move over warm water creating favorable conditions for development, but it is likely to encounter wind shear by midweek, AccuWeather hurricane expert Dan Kottlowski said.

Also under observation is a broad area of low pressure that is forecast to move over the southwestern Caribbean early next week.

Its path is uncertain, but “there is a chance it could affect Cuba, the Bahamas and perhaps the Florida Peninsula either directly or indirectly during the fourth week of October,” Kottlowski said.

Because 2020 is a La Niña year, forecasters expect late-season storm activity to increase in October and possibly even carry into November.

Meanwhile, a third disturbance located near the far eastern boundary of the Caribbean Sea on Thursday is forecast to bring heavy rain to parts of the region in the next few days.

Rain is forecast for the southeastern Caribbean as the system passes over the Virgin Islands and Puerto Rico on Thursday and Haiti and the Dominican Republic on Friday. But, its odds of developing into a tropical system stood at 0% Thursday due to the presence of storm-shredding wind shear.

The busy 2020 hurricane season, which has had 25 named storms, is rivaling the 2005 season, which had a record 27 named storms.

Remarkably, none of the storms that have made landfall in the continental U.S. this year have hit Florida. October storms often threaten Florida as they move north and then northeastward.

The next storm to form would be called Epsilon.

Hurricane season officially ends Nov. 30.

South Florida Sun Sentinel staff writer Chris Perkins contributed to this report.


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