Model-Based Robotic Cell Aspiration: Tackling the Impact of Air Segment

Abstract

Cell aspiration is a common micro-manipulation technique for cell transfer, particularly in in vitro fertilization (IVF) procedures. The minuscule volume of a cell (pL) and limited damping provided by the medium make it challenging to accurately and quickly aspirate a cell to the desired position inside the micropipette. Experienced clinicians intentionally insert an air segment inside the micropipette in advance to make the aspiration easier. Nevertheless, the unclear damping effects and the varying initial length of the air segment in each aspiration pose difficulties for most operators. Inadequate judgment and response may lead to overshoot or even loss of the cell. This paper constructs a nonlinear dynamics model to elucidate the cell motion inside a micropipette containing an inserted air segment. The model reveals the impact of the air segment. A model-based controller is designed to facilitate the accurate aspiration of human sperm to a desired position, incorporating an estimated initial length of the air segment. Experiments were conducted to quantitatively evaluate the performance of both the model and the controller involving various initial air segment lengths. The results demonstrated a 100 % success rate in 50 sperm aspiration experiments, achieving an average positional accuracy within <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 2$</tex> pixels and an average settling time of 5.89 seconds.