Active Sealing using Squeeze Film Levitation

Abstract

In laparoscopic surgery, maintaining a pressurised workspace within the intra-abdominal cavity is crucial for the minimally invasive procedure's success. Trocars play an essential role by sealing the cavity during surgery and providing access to surgical instruments. However, conventional trocar seals involve a fundamental trade-off between preventing gas leaks and reducing instrument friction and haptic feedback loss. In response to these challenges, this thesis investigates a novel active trocar sealing system based on the principle of Squeeze Film Levitation (SFL). This approach utilises high-frequency vibrations to create a pressurised gas film at the seal-instrument interface, aiming to achieve both frictionless manipulation and active gas flow control. The primary objective of this numerical investigation was to evaluate the feasibility of employing SFL for dynamic sealing against typical surgical pressure differentials. Initial analyses indicated that while specific SFL configurations effectively generate levitation (indicative of friction reduction), these could, in some instances, intensify gas outflow. However, the research demonstrated that optimised SFL system configurations can potentially achieve net inward gas pumping, actively reversing the direction of gas flow against the pressure difference. This capability represents a significant advancement over traditional sealing methods, moving beyond merely restricting leakage. The study identified distinct operational regimes, governed by the intricate interplay between the system's inherent fluid dynamics and key design parameters, such as geometric configurations and actuation timing. Findings suggest that careful tuning of these parameters fundamentally drives the system's dynamic response, observing outcomes ranging from enhanced flow restriction to substantial inward pumping. This work establishes the SFL system as a promising application for active dynamic sealing. Its demonstrated ability to control the gas flux direction, combined with the inherent low-friction characteristics of SFL, suggests a strong potential for improving pneumoperitoneum stability and surgical instrument interaction, with broader implications for precision fluid and gas control in diverse engineering applications.