A wrist for needle-sized surgical robots

TLDR

Needle‑sized surgical tools could be more useful if they can navigate sharp corners, but optimizing such a design is difficult due to many parameters and material nonlinearities. The study introduces a wrist that enables corner navigation and evaluates selected geometries through kinematic and static modeling. The wrist is a nitinol tube with asymmetric cutouts actuated by a tendon, easily interfaced with manual tools or concentric‑tube robots and inexpensive to manufacture. Prototype experiments with a 1.16 mm diameter wrist confirm the accuracy of the derived kinematic and static models.

Abstract

The needle-sized surgical tools used in arthroscopy, otolaryngology, and other surgical fields could become even more valuable to surgeons if endowed with the ability to navigate around sharp corners to manipulate or visualize tissue. We present a needle-sized wrist design that grants this ability. It can be easily interfaced with manual tools or concentric tube robots and is straightforward and inexpensive to manufacture. The wrist consists of a nitinol tube with several asymmetric cutouts, actuated by a tendon. Perhaps counter-intuitively, within this seemingly simple design concept, design optimization is challenging due to the number of parameters available and nonlinearities in material properties. In this paper, we examine a subset of possible geometries and derive kinematic and static models. Experimental results with a 1.16 mm diameter prototype validate the models. Lastly, we provide a discussion summarizing the lessons learned in our early experience designing and fabricating wrists of this type.