Background: Needle insertion is commonly used in minimally invasive surgery. Cannula flexible
needle, as one of the insertion needles is composed of a flexible cannula and a flexible stylet, both of which
need to be driven independently. The coordination control of both motions can achieve a variety of 3D insertion
paths according to recent patents.
Objective: This paper is to innovatively design an insertion mechanism for the cannula flexible realizing the coordinated
motions of both the cannula and the stylet.
Methods: Based on the analysis of the required degrees of freedom and motion models of the cannula flexible
needle, the general scenario of the insertion mechanism was designed by using TRIZ theory. The condition for
achieving the linear insertion path was obtained based on the analysis and calculation of the screw motion by
using the screw theory.
Results: The general scenario of the insertion mechanism was innovatively obtained, the spiral slide and the
cross linear slide were adopted, and furthermore, the parameters of the spiral slide were determined, along with
the design of cross linear slide. At last, the virtual prototype was achieved.
Conclusion: In this paper, the TRIZ theory was used to innovatively design an insertion mechanism for the
cannula flexible needle, and both the general scenario and the concrete parts were achieved. The result showed
rationality of the designed insertion mechanism fulfilling all the requirements for the cannula flexible needle.