Dynamic study of the piezo-driven pipettes in intracytoplasmic sperm injection
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Intracytoplasmic Sperm Injection (ICSI) is regarded as a critical assisted reproductive technology (ART) procedure in which a single spermatozoon is mechanically injected into the cytoplasm of an oocyte using an injection pipette. During ICSI, one piezo-driven actuator (PDA) connected to the pipette is routinely utilized. Importantly, the pipettes driven by PDA are typically filled with the mercury plug. The presence of mercury is associated with serious potential toxicity effects, both related to personnel safety and to the developmental competence of the manipulated oocytes. Therefore, this research is developed to analyze the effects of mercury on the dynamic characteristics of the piezo-driven pipette, and to achieve the improved method to replace mercury. The lateral vibration of the injection pipette is first analyzed, the finite element model including the effects of the fluids both inside and outside the pipette is built up, and the transient responses of the pipette are obtained by the numerical simulations. Based on the dynamic model of PDA connected to the pipette, the longitudinal vibration of the pipette is studied as well. The role of the small momentum diffusivity of mercury is specifically investigated in facilitating the ICSI procedures. "Scissor theory" is proposed to explain the function of mercury in details. Based on the simulation results, our PDA system is developed. Numerous preliminary experiments are performed with the commercial Piezo-driven systems and our system. Our system is more efficient than the present commercial systems with the presence of mercury plug; furthermore, our system does work successfully in penetrating mouse oocytes without mercury plug.
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