On-Chip Automated Acoustofluidic Three-Dimensional Observation System for Oocytes*

Single-cell manipulation techniques are an important topic in medical and biological research, especially in assisted reproductive technology. The traditional method of observing oocytes through contact manipulation using a capillary is inefficient, requires a high level of skill, and poses potential damage to the oocytes. Therefore, we propose an on-chip acoustofluidic system for the automated observation of oocytes. Multiple trap chambers allow for the simultaneous capture of multiple cells, increasing operational efficiency. Fluid-based trapping and acoustofluidic-driven rotation reduce the probability of oocytes encountering sharp ends, making them less susceptible to damage. Our system has been tested and proven capable of rotating the oocyte in both in-plane and out-of-plane directions, which enables the adjustment of the oocyte to an arbitrary orientation in space. The whole process does not involve the movement of the focal plane. By combining the proposed automated oocyte position recognition method with the pulse width modulation-based position control method, we achieved a maximum speed of 1.4 revolutions per second and a minimum control accuracy of less than 1.6°, making it user-friendly with almost no operational threshold.