Applications of Acoustic Waves in Micro-Droplet Technologies

Acoustofluidics has emerged as a powerful technique for the precise generation, sorting, manipulation, and stimulation of cell-laden droplets within emerging droplet microfluidic studies. Droplet acoustofluidics leverages various mechanisms, including acoustic radiation forces and acoustic streaming, to actively manipulate droplets non-invasively. The remarkable speed, precision, and biocompatibility of acoustic waves make it an ideal tool for droplet-based single-cell-level biomedical research. This review paper provides a comprehensive overview of recent advancements in droplet acoustofluidics technologies, highlighting their mechanisms, advantages, applications, and challenges. We have compiled the fundamental principles of acoustic waves and summarized major applications, including single-cell droplet generation, sorting, and active in-droplet manipulation. Despite the advances that current droplet acoustofluidics have achieved, we point out the challenges and give out our thoughts on future improvement directions. These insights will have important implications for advancing interdisciplinary research in cell mechanobiology, drug screening, cell sorting, and mechanophenotyping.