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.
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