Structure Design And Analysis Of Cannula Flexible Needle And Its Puncture Mechanism

Minimally invasive surgery has become a new therapeutic method. And it is with small trauma, quick effect, less pain and some other advantages, which has been favored by the contemporary medical field. In order to overcome the disadvantage that the rigid needle cannot puncture around the obstacle like bone to achieve targeting puncture, the concept of flexible needle has been put forward by some scholars. Aiming at the shortcomings of the traditional flexible needle, difficult to realize path correction and accuracy control of the oblique tip of the flexible needle, a cannula flexible needle has been proposed in this thesis. The above problems have been solved effectively by using cannula flexible needle. In this thesis, the stress and bending properties of the cannula flexible needle have been analyzed, and cannula flexible needle and its puncture mechanism have been optimized.Firstly,the mechanical model of needle tip force has been established, the best needle tip angle has been obtained by fitting the force test results of different oblique needle tip angles. Based on the tissue parameters, the calculation method of cutting angle of needle tip has been proposed by analyzing the stress of needle tip slope and using the energy principle.Secondly, the core needle and tube diameter of the cannula flexible needle has been optimized through the analysis of the cantilever model deflection. After the needle shaft force has been analyzed, the main force which makes the needle bending has been found. The bending properties of the cannula flexible needle have been simulation study by the finite element analysis software, and the bending trend of the cannula flexible needle has been qualitative analyzed.Thirdly, the innovative design of cannula flexib le needle has been done by applying TRIZ and based on analyzing the degree of freedom of cannula flexible needle. The distribution of guide block s upporting the needle axis has been optimized by finite element analysis, in order to prevent the warp of needle axis when force applied. And the reasonability of guide blocks distribution has been proved by simulation results.Finally, the puncture laboratory furniture of the cannula flexible needle has been established. The friction coefficient between the needle and the bionic tissue has been measured. And the experiments about optimization results of tip angle have been finished. Prototype of the cannula flexible needle has been made by ABS. Simulation experiments have been finished, and the bending properties of the cannula flexible needle have been verified.The stress of the tip of the cannula flexible needle and bend properties of the needle have been researched in this thesis. The cannula flexible needle and its puncture mechanism have been optimized and innovative designed. At last, the experimental verification is carried out. It lays a theoretical and experimental foundation for the further study of the cannula flexible needle.