Robotic 3-DoF rotation of oocytes driven by acoustic microstreaming

The rotational operation of oocytes plays a critical role in embryo engineering, particularly in assisted reproductive technology, cloning, and gene research. The conventional manual method relies heavily on operator experience and repetitive trial-and-error processes, while existing automated contact-based techniques require complex force control. Although hydrodynamic approaches enable non-contact rotational operations, three-degree-of-freedom (3-DoF) rotation remains unavailable. Here, we propose an acoustically driven 3-DoF rotation method for embryo engineering. By leveraging multiple acoustic microstreaming flows induced by the dynamic responses of microbubbles and microstructures to an acoustic stimulus, we achieve controlled rotation of oocytes about the x, y, and z axes within on-chip chambers. A piezoelectric transducer generates the acoustic field, where the driving frequency determines the rotation direction, and the input amplitude modulates the rotational velocity. Furthermore, stable 3-DoF rotation facilitates high-quality 3-D oocyte reconstruction, outperforming unidirectional rotation methods. Given the diverse oocyte rotation methods developed to date, our approach offers superior degrees of freedom, enhanced controllability, and improved biocompatibility, broadening its potential applications in embryo engineering.