The power of sound

It is a peculiarity of research that the popularity or success of a particular field over time is somewhat unpredictable. It is rarely just hard work and determination that lead to breakthroughs, but often a flexible approach and the ability to recognise new opportunities. This appears to be the case for sonochemistry, the application of ultrasound to chemical processes and reactions. After years of taking a backseat in the UK, the range of possibilities this technique can offer are now being realised.

The RSC's Sonochemistry interest group began over 20 years ago. Tim Mason, from Coventry University, has been involved with the group from the beginning and is currently the group's chairman. A successful seminar at the RSC's Annual Congress in 1986 led to its formation. For the first decade of the group's existence, Mason says, growth and interest were good.

There were residential courses to teach the theoretical and practical aspects of sonochemistry to researchers and joint meetings in such areas as medicinal chemistry. International collaboration was strong, especially after the formation of the European Society of Sonochemistry in 1990. However, over the last decade, the group experienced a downturn.

Although there was much activity in Europe and the USA, interest waned in the UK. "For some reason, that I really can't explain," says Mason, "things went a bit flat in the UK. I think the field was seen as a bit odd by researchers."

Resurgence

In the last couple of years however, activity has started to take off again for sonochemistry in the UK.  Researchers and industry have begun to employ the wider applications of ultrasound beyond synthesis.

Ultrasound can be used to deliver chemotherapeutic drugs to targeted tumours, create nanoparticles, sterilise food and purify water.

"Initially our group started with an emphasis on synthesis, as that is where our original members' interests lay," says Mason, "but we are now putting ourselves on a far broader footing. Perhaps the term sonoprocessing is a better one than sonochemistry. It emphasises the wide variety of applications and multi-disciplinary approach of the subject."

Christian Jones, secretary of the Sonochemistry group, has first-hand experience of developing ultrasound-based technologies for industry. He is Business Development Manager at Prosonix Limited, an Oxford-based company that has devised a range of ultrasonic processes that demonstrate the range of problems it can help tackle.

Prosonix has developed a method of using ultrasound to nucleate crystals from solution. This sonocrystallisation allows for better control of crystal growth, producing high quality, pure crystals. More control means that crystals can also be grown with more desirable shapes, improving their flow and filtration properties.

Last year, Prosonix won the RSC Teamwork in Innovation award for their development of SAX (Solution Atomisation and Crystallization by Sonication) technology. This process produces micro and nano-crystalline pharmaceutical ingredients and drug formulation with improved properties, especially for drugs that will be inhaled.

Before Prosonix's work, Jones says, sonochemistry was seen as an obscure range of phenomena that could be investigated in the laboratory but not scaled up to industrial use. With proven new applications, both industry and academia are becoming more interested in the topic.

Gearing up

In January of this year, the Sonochemistry group held a joint meeting with the Formulation Science and Technology group. Molecules to Particles showcased three areas where ultrasound technology can contribute to the production of pharmaceutical products: synthesis, processing of particles and analysis. The meeting was a great success with both academic and industrial involvement and international attendance.

Spurred on by the success of the meeting, the group is keen to push on with its strategy of emphasising the multi-disciplinary nature of ultrasound technologies. Mason believes they need to get disciplines beyond chemistry involved, including maths, engineering, physics and materials. He hopes to arrange meetings that will bring together experts to discuss sonochemistry applications in medicine and nanotechnology. He also suggests tagging symposia onto other meetings, showcasing how sonoprocessing can be a useful aid in a wide variety of fields.

Both Mason and Jones agree that industry in the USA is an important constituency to reach and they are hoping to run a joint meeting with American colleagues.

Mason is optimistic on the group's development. "By focusing on process enhancement, we can get kicking away in many more areas. The future is sono."