A Mechanics-Based Model for 3-D Steering of Programmable Bevel-Tip Needles

We present a model for the steering of programmable bevel-tip needles, along with a set of experiments demonstrating the three-dimensional steering performance of a new, clinically viable, 4-segment, preproduction prototype. A multibeam approach based on Euler-Bernoulli beam theory is used to model the novel multisegment design of these needles. Finite element (FE) simulations for known loads are used to validate the multibeam deflection model. A clinically sized (2.5 mm outer diameter), 4-segment programmable bevel-tip needle, manufactured by extrusion of a medical-grade polymer, is used to conduct an extensive set of experimental trials to evaluate the steering model. For the first time, we demonstrate the ability of the 4-segment needle design to steer in any direction with a maximum achievable curvature of (0.0192 ± 0.0014 mm -1 ). FE simulations confirm that the multibeam approach produces a good model fit for tip deflections, with a root-mean-square deviation (RMSD) in modeled tip deflection of 0.2636 mm. We perform a parameter optimization to produce a best-fit steering model for experimental trials with a RMSD in curvature prediction of 1.12 × 10 -3 mm -1 .