The Needle With Lancet Point: Geometry for Needle Tip Grinding and Tissue Insertion Force

The grinding procedure and setup, the cutting edge inclination and rake angles of the needle with lancet point (NLP), and the NLP tissue insertion force are investigated in this paper. The NLP is the most commonly used needle tip geometry. However, there is a lack of research on the NLP grinding and cutting edge characteristics. In this study, a four-step grinding procedure and a mathematical model to calculate the inclination and rake angles along the cutting edge of the NLP are developed. Three cases of NLP are defined based on the relative position of the lancets. Prototype NLP for each case was produced and analyzed. Compared to the regular bias bevel needle, grinding two lancets in NLP can increases the inclination angle, particularly at the needle tip. Experiments with needle insertion into the porcine liver were conducted and results showed that NLP could achieve over 40% reduction of the initial peak needle insertion force compared to that of the regular bias bevel needle tip.