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Sorry for my delayed answer. When the Piezo drive unit is driven, the physical force is produced like hitting the micropipette with a hammer. This physical force produces ultra-fast sub-micron forward momentum of the micropipette tip, however, the operation liquid filled inside the micropipette stays still, because of inertia. As a result, ultra-fast submicron negative pressure is produced at the tip of the micropipette. The Piezo-ICSI uses this negative pressure produced by ultra-fast sub-micron forward momentum which is generated by the Piezo drive unit. And the flat tip micropipette is used because to equalize the negative pressure applied at the tip of the micropipette.

Thank you so much for your questions and sorry for my delay response. My fertilization rates with this method are as follows. Head-first injection group: 86% (294/342) Tail-first injection group: 90% (262/290) (Hiraoka K et al., J Obstet Gynaecol Res. 2018 Oct;44(10):1963-1969.) No significant difference was observed between the Head-first and Tail-first groups, but a slightly higher fertilization rate was observed in the Tail-first group, so I inject the sperm from Tail-first. But either's fine!

Thank you, Dr Hiraoka. And in terms of time consuming, do you think piezo icsi takes more time to perform than conventional icsi?

@@biryukovaa Yes, I think so. The rough time of pipette preparation, sperm immobilization and zona opening to sperm injection are as follows. Because of the procedure of introducing Fluorinert inside the micropipette and zona opening, Piezo-ICSI takes more time at pipette preparation and zona opening to sperm injection. Time of pipette preparation Conventional-ICSI (C-ICSI): 60s Piezo-ICSI (P-ICSI): 100s Time of sperm immobilization C-ICSI: 20s P-ICSI: 15s Time from zona opening to sperm injection C-ICSI: 25s P-ICSI: 50s