Design and Simulation Optimization of a Novel Oocyte Ultrasonic Micro-dissection Instrument

The zona pellucida (ZP) micro-dissection technology has played a key role in the field of artificial assisted reproduction (such as ZP thinning, preimplantation genetic diagnosis (PGD), etc.). Currently, laser ZP micro-cutting technology using far-infrared beam has the disadvantages of high price, thermal damage, and low degree of freedom. Piezoelectric ultrasonic micro-cutting technology has matured at the biological tissue level, but ultrasonic cutting at the single-cell level is still difficult to achieve. In this paper, based on piezoelectric ultrasonic tissue micro-cutting theory, the mechanism of ultrasonic cutting of the oocyte ZP was researched, and a cutting method for the ZP was proposed. Based on the design formula of flexure's stiffness, this paper analyzes the effects of dimension parameters on the vibration condition of micro-needle. An ultrasonic cell surgery instrument based on a three-dimensional stereoscopic flexure-guided structure was designed. The modal analysis and the harmonic response analysis of the structure were performed using finite element software. The experimental results show that the lateral amplitude of the newly designed device's needle tip is smaller than the traditional one in the specified range of frequency. Among them, when the operating frequency is around 22.1 kHz, the lateral amplitude of the needle tip is reduced to $0.021\mu \mathrm{m}$ . Finally, the theoretical method of piezoelectric ultrasonic cutting on single cell layer is presented for the first time, which has a broad prospect and significance for artificial assisted reproduction.