The Caturo: A Submillimeter Diameter Glass Concentric Tube Robot with High Curvature

Abstract

Concentric tube robots (CTRs) are considered promising in medical applications involving intracorporeal confined spaces, high dexterity, and 3D path following. Most CTRs are currently made of Nitinol due to its superelastic properties and biocompatibility. Herein, glass–polymer composite tubes to ease the shape setting, decrease friction, and benefit linear elasticity are proposed. A new generation of CTR: Caturo, which is made of flexible and miniaturized submillimeter glass–polymer tubes, is presented. Caturo has also an unprecedented radius of curvature that reaches as low as 5 mm. It is fabricated through the thermal treatment of a thin heat-shrink polymer tube on a glass capillary in a 3D-printed mold. The fabrication process is quick, versatile, and relatively low cost. Various free space deployment operations are demonstrated, such as 3D helical precurved tube deployment, conical–spiral deployment, and constrained 3D deployment through needle orifices. The forward kinematic model (FKM), inverse kinematic model (IKM), and stability analysis are experimentally validated. Finally, precurved optic fiber deployment with laser emission capability, fluid sample suction, and delivery operation is proposed. There is also a proposed vitreoretinal surgery using a fish-eye under optical coherence tomography (OCT) visualization.