The tip interface mechanics modeling of a bevel-tip flexible needle insertion

As a bevel-tip flexible needle is inserted through soft tissue, the asymmetry of the needle tip conducts the needle bending naturally. The needle inside the tissue can follow a desired trajectory via controlling the direction of the asymmetrical tip. If the force between the needle and the soft tissue is explicit, the needle can be controlled to escape from obstacles and reach target lesions as accurately as possible, so a mechanics modeling between the flexible needle and the soft tissue is particularly important. In this paper, based on the consideration of friction force, the interaction of needle tip and soft tissue is modeled and analyzed during the needle linear feeding and axial rotating. In the analytical model, the forces applied on the bevel tip are formulated based on the geometry of the bevel edge and material properties of soft medium. Meanwhile, the relationship between the forces generated on the bevel-tip and the major influence factors is obtained, which is described in the several figures and also further discussed in detail. The concept and approach outlined in this paper is generic which can be extended to a variety of flexible needle insertion involved applications.