A new flow-based design for double-lumen needles.

Oocyte retrieval forms a crucial part of in vitro fertilisation treatment and its ultimate outcome. Standard double-lumen needles, which include a sequence of aspiration and flushing steps, are characterised by a similar success rate to single-lumen needles, despite their increased cost. A novel hydrodynamics-based needle called the OxIVF needle is proposed here, which is geared towards the generation of an internal flow field within the full follicular volume via laterally, rather than frontally, oriented flushing, leading to successful retrievals with no additional stress on the oocyte. A two-dimensional digital twin of the follicular environment is created and tested via multi-phase flow direct numerical simulation. Oocyte initial location within the follicle is varied, while quantities of interest such as velocity magnitude and vorticity are measured with a high level of precision. This provides insight into the overall fluid motion, as well as the trajectory and stresses experienced by the oocyte. A comparative benchmark set of tests indicated a higher success rate of the OxIVF needle of up to 100%, marking a significant improvement over the traditional double-lumen design whose success rate of no more than 75% was also highly dependent on the location of the needle tip inside the follicle. All forces measured during these tests showcase how the oocyte experiences stresses which are no larger than at the aspiration point, with the flow field providing a gentle steering effect towards the extraction region. Finally, the flow generation strategy maximises oocyte yield, unlocking new capabilities in both human and veterinary contexts.
Competing Interests: Declaration of competing interest All co-authors confirm that this research received additional support from an organisation beyond the authors’ academic institutions. All co-authors confirm that there are no personal financial interests or professional relationships to disclose outside of their professional practice. All connections and activities have been made known through the Acknowledgements section in the manuscript as follows: Dr. Radu Cimpeanu gratefully acknowledges the support of the Mathematical Institute at the University of Oxford through funding via the Hooke Research Fellowship and access to the departmental high performance computing facilities that supported the work reported here. All authors are thankful to Oxford University Innovation for funding obtained via the University Challenge Seed Fund supporting the most recent stages of this study, as well as helpful discussions in the early stages of the investigation. The following patents: #eP4033991A1, US20220323112A1, WO2021058961A1 are relevant to the work submitted for publication herein, with all co-authors listed as inventors, and Oxford University Innovation Ltd. as current assignee. The respective patents are currently pending.
(Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)