Novel Three-Segment Steerable Continuum Needle Manipulator for Minimally Invasive Surgery

Due to their flexible bodies and high length-to-diameter ratios, continuum robots are uniquely suited for tasks requiring deep access into narrow pathways. This article presents a novel three-segment steerable continuum needle (TSSCN), in which the segments are longitudinally split and function as integrated tendons, eliminating conventional disk structures. This design reduces component count and enables miniaturization for broader medical applications. The TSSCN comprises a three-segment tube (TST) as the main body, two outer tubes, an inner support tube, and an optional tool. The TST is fabricated using superelastic nickel–titanium alloy and is cut using a femtosecond laser to create distal and proximal segments, enabling the TSSCN to achieve a 1.2-mm diameter. Pushing or pulling the proximal end of the TST deforms the TSSCN, causing the distal end to bend into a shape that minimizes elastic potential energy under resistance from the outer tube. Geometric models are employed for forward and inverse kinematics analysis, and their effectiveness is validated experimentally. The TSSCN achieves bending angles exceeding 180° and features an adjustable bending arc length, and its potential for middle-ear surgery is experimentally tested. Therefore, this type of TSSCN has the potential to be applicable to various minimally invasive surgical procedures with minor modifications.