Crystallization, an essential process for industries like medicine and food production, has reached a new milestone thanks to fresh research from a team led by Profesor Duyang Zang and Xiaoqiang Zhang at Northwestern Polytechnical University in Xi’an, China. Their inventive use of sound waves to influence how saltwater droplets evaporate and form crystals was recently detailed in Ultrasonics Sonochemistry. This work demonstrates how ultrasound can make crystals smaller and more consistent while speeding up the process, with promising industrial applications.
Professor Zang and his team examined how two types of ultrasound waves—standing and traveling—affect the evaporation and crystallization of salty water droplets. Standing waves are stationary sound patterns created by reflected waves, while traveling waves move continuously in one direction. Their discoveries underline the exciting potential of ultrasound to improve crystal quality, creating smaller and more uniform structures. “This technique not only accelerates evaporation but also significantly reduces crystal size, making it an invaluable tool for precision needs,” Professor Zang shared.
One of the key findings of this study is the distinct effect of different sound wave types. Traveling sound waves resulted in much finer crystals compared to standing waves. For example, crystals exposed to traveling waves were noticeably smaller and more uniform than those formed naturally, showcasing the remarkable control ultrasound provides. Meanwhile, standing waves also reduced crystal size, though to a lesser degree. These differences are linked to how ultrasound energy boosts the formation of tiny starting points for crystal growth, called nuclei, and increases their number.
The broader benefits of this research are impressive. Smaller, more refined crystals can enhance how medications are absorbed by the body, improve the strength of processed metals, and make chemical production more efficient. The team also explained why ultrasound has this effect. When sound waves create tiny bubbles that expand and burst, known as cavitation, they help break up larger crystals and encourage the formation of smaller ones.
“This research gives us new ways to manage the crystallization process,” Zhang explained. “By using sound energy, we can create more precise and efficient processes that are valuable across many industries.”
The findings highlight how adjusting sound wave settings can achieve the best results. For instance, in traveling wave setups, the position of the droplet relative to the sound source greatly influenced the outcome. Droplets placed at specific distances produced much finer crystals, demonstrating the fine-tuned control this method offers.
The implications of this work are game-changing. By applying ultrasound to guide crystallization, industries 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 essential.
Journal Reference
Zhang, X., Chen, H., Wang, Y., Gao, X., Wang, Z., & Zang, D. “Ultrasound induced grain refinement of crystallization in evaporative saline droplets.” Ultrasonics Sonochemistry, 2024. DOI: https://doi.org/10.1016/j.ultsonch.2024.106938
About the Authors
Duyang Zang received a PhD in Physics from Paris-Sud University in 2010. He is now a professor in the School of Physical Science and Technology, Northwestern Polytechnical University, China. He works on the physics and dynamics of soft matter interfaces, including capillary phenomena, interfacial rheology, droplet/bubble dynamics, phase behaviors in complex and soft matter systems. In the last 10 years, he has conducted more than 10 scientific projects granted from the National Natural Science Foundation of China, Ministry of Education, etc, and tried to combined the study of soft matter with acoustic levitation. He authorized more than 90 peer-reviewed journal papers including Nature, Nature communications, Physics Reports, Soft Matter, Physical Review Fluids etc., and 5 book chapters. He has also published 2 books. His publications have been cited more than 2700 times with h-index of 30 (Scopus). He has won the “top 10 Emerging Scientists Award of China, 2018” and IAAM Scientist Medal 2021. He is the Fellow of IAAM, the editorial board member of European Physical Journal E, Frontiers in Soft Matter and advisory board of Soft Matter.
Xiaoqiang Zhang received the B.S. degree in Packaging Engineering from Shaanxi University of Science & Technology, Xi’an, China, in 2015 and the M.S. degree in Packaging Engineering from Xi’an University of Technology, Xi’an, China, in 2019. He is currently working toward the Ph.D. degree in Physics with the School of Physical Science and Technology, Northwestern Polytechnical University, Xi’an, China. His research interests include evaporative crystallization of liquid, ultrasonic crystallization and ultrasonic levitation and freezing. He has published more than 10 SCI papers and holds 2 authorized invention patents.
