A study on the effect of the number of expansion units in a microfluidic chip on hyaluronidase-free oocyte denudation in mammals.

In Vitro Fertilization (IVF) and Intracytoplasmic Sperm Injection (ICSI) are well-known fertility treatments that, due to resource-intensive, high degree of expertise required, and frequent subpar performances, often yield in high costs for treatment cycles. Microfluidic technology has enabled cost-effective egg-handling procedures towards new assistive reproductive devices: oocytes are subjected to microchannels with jagged surfaces to let shear stress remove undesirable cumulus cells, and microchannels with expansion units facilitate the transport of oocytes in chips. However, although the previous works have studied the influence of shear stress on oocyte denudation and the role of microchannel teeth in optimizing cell handling efficiency, the study of configurations of jagged surfaces and expansion units in microfluidic devices has remained elusive. Also, comprehensive analysis using both computational fluid dynamics (CFD) and real-world microfluidic devices has remained an unexplored area. To fill the abovementioned gap, this paper studies microfluidics chips with different expansion units to depict the behavior of oocytes when subjected to controlled input flows. The proposed chips were developed and fabricated using a direct engraving CO₂ laser machine on polymethyl methacrylate (PMMA) sheets and bonded in a natural ventilation lab oven, rendering the highly efficient and low-cost microfluidic chips for oocyte denudation. The effect of the expansion units has been investigated in CFD simulation and real lab experimentation with mature buffalo oocytes at a constant flow rate, and a chip with five expansion units arranged in two lines achieved 98.33% denudation efficiency, low-cost fabrication (about 1 USD), and quick fabrication time (about 20 minutes).