Experimental characterisation of a biologically inspired 3D steering needle

Percutaneous intervention is a popular minimally invasive surgical technique, as it offers many potential advantages for the patient. Research efforts to date have focussed on improving the accuracy and applicability of this procedure through robotic control, in particular with the application of needle steering systems. Previously, we demonstrated two-dimensional (2D) steering within gelatine, with a prototype of a novel biologically inspired multi-segment needle, the STING. Then, a novel `programmable bevel´ concept, where the steering angle of the needle is a function of the offset between segments, was used to control the trajectory taken within the steering plane. This paper presents our first attempt to demonstrate controllable three-dimensional (3D) steering with a new four-segment prototype of the STING. We show that an approximately linear relationship exists between segment offset and curvature of the tip path for a single leading segment, as well as for two segments which are moved forward of the others by an equal amount. This characterisation is then demonstrated with 3D open loop experiments, which show that the established behaviour is applicable for controlled 3D steering along eight principal directions.