Parametric study for asymmetric flexure hinge design for tissue cutting

This article presents empirical stiffness equations for a novel compliant needle mechanism that will aid in ultrasonic tissue cutting. Needles are an often used medical tool that cut tissue with minimal damage. Ultrasonic vibrational cutting has been shown to reduce insertion forces necessary to cut, thus minimizing deflections of the tissue and needle. A previous study has demonstrated that coupling this ultrasonic vibration with a compliant hinge generates a transverse cutting motion. This work explores the compliant hinge design and presents empirical stiffness equations that can be used to model the needles compliant motion. The empirical model prediction, when compared to experimental findings, is shown to have an average error less than 8% when the distance between the hinges is kept within 1.68 times the thickness of the hinges. With these equations it will be possible to optimize the compliant needle design for tissue cutting.