Crystallization, an important process in industries such as medicine and food production, has reached a new milestone thanks to the latest research by a team led by Professor Duyang Zang and Professor Zhang Xiaoqiang of Northwestern Polytechnical University in Xi’an, China. They creatively used sound waves to influence the way brine droplets evaporate and form crystals, which was recently detailed in Ultrasonic Sonochemistry. The work shows how ultrasound can make crystals smaller and more consistent while speeding up the process, which has broad industrial applications.
Professor Zang and his team studied how two types of ultrasound waves (standing waves and traveling waves) affect the evaporation and crystallization of salt water droplets. Standing waves are stationary sound patterns produced by reflected waves, while traveling waves move continuously in one direction. Their findings highlight the exciting potential of ultrasound to improve crystal quality and create smaller, more uniform structures. “This technology not only accelerates evaporation, but also significantly reduces the crystal size, making it a valuable tool for precision needs,” Professor Zang shared.
One of the key findings of this study is the unique effect of different sound wave types. Traveling sound waves produce much finer crystals than standing waves. For example, crystals exposed to traveling waves were significantly smaller and more uniform than naturally occurring crystals, demonstrating the superior control afforded by ultrasound. At the same time, standing waves also reduce crystal size, albeit to a lesser extent. These differences relate to how ultrasonic energy promotes the formation and increases the number of tiny starting points for crystal growth, called nuclei.
The broader benefits of this research are impressive. Smaller, more refined crystals could enhance the way drugs are absorbed into the body, increase the strength of processed metals, and make chemical production more efficient. The research team also explains why ultrasound has this effect. When sound waves create tiny bubbles that expand and collapse (called cavitation), they help break up larger crystals and encourage the formation of smaller crystals.
“This research provides us with a new way to manage the crystallization process,” Zhang explains. “By using sound energy, we can create more precise and efficient processes that will be valuable to many industries.”
The findings highlight how to adjust sonic settings to achieve optimal results. For example, in a traveling wave setup, the position of the droplet relative to the sound source greatly affects the results. Droplets placed at specific distances produced finer crystals, demonstrating the fine-tuned control provided by this method.
The implications of this work are game-changing. By applying ultrasound to guide crystallization, industry can achieve better results with less effort. This innovation promises exciting applications in areas such as advanced materials and environmentally friendly manufacturing, where controlling the size and structure of particles is critical.
Journal reference
Zhang, X., Chen, H., Wang, Y., Gao, X., Wang, Z., and Zang, D. “Ultrasound-induced grain refinement of crystallization in evaporated brine droplets.” Ultrasonic Sonochemistry , 2024.
About the author
Du Yangzang He received his PhD in physics from the University of Paris-Sud in 2010 and is currently a professor at the School of Physical Science and Technology at Northwestern Polytechnical University. He works on the physics and dynamics of soft matter interfaces, including capillary phenomena, interfacial rheology, droplet/bubble dynamics, and phase behavior in complex and soft matter systems. In the past 10 years, he has presided over more than 10 research projects from the National Natural Science Foundation of China and the Ministry of Education, and has tried to combine soft matter research with sound levitation. He has authored more than 90 peer-reviewed journal articles, including Nature, Nature communications, Physical Reports, Soft Matter, Physical Review Fluids, etc., as well as 5 book chapters. He has also published 2 books. His publications have been cited over 2700 times and have an h-index of 30 (Scopus). He has won the “2018 China’s Top Ten Emerging Scientists Award” and the 2021 IAAM Scientist Medal.
Zhang Xiaoqiang He received a bachelor’s degree in packaging engineering from Shaanxi University of Science and Technology in 2015 and a master’s degree in packaging engineering from Xi’an University of Technology in 2019. Graduated from the School of Physical Science and Technology of Northwestern Polytechnical University with a doctorate in physics. His research interests include liquid evaporation crystallization, ultrasonic crystallization, and ultrasonic suspension and freezing. He has published more than 10 SCI papers and holds 2 authorized invention patents.
