Miniature Continuum Manipulator With Three Degrees-of-Freedom Force Sensing for Retinal Microsurgery

Retinal microsurgery requires the precise manipulation of delicate tissue in the interior of the eye. Smart surgical instruments with dexterous tip and force sensing capabilities can permit surgeons to perform more flexible surgical procedures and obtain imperceptible force information, thereby improving the safety and efficiency of microsurgery. In this study, we present an intraocular continuum manipulator with three degrees-of-freedom (DOF) force sensing capabilities. A contact-aided compliant mechanism based on cutting superelastic Nitinol tubes is used to provide high dexterity. It enables two rotational DOFs at the distal end of the manipulator. Fiber Bragg grating (FBG) fibers are used to provide high-resolution force measurements. Moreover, a novel Nitinol flexure was designed to achieve high axial force sensitivity. The experimental results show that the maximum bending angle of the dexterous tip is more than ±45 deg for each DOF with high repeatability. In addition, the experimental results demonstrate that the proposed force sensor can provide sub-millinewton resolution. The manipulator has also been validated with an artificial eye model, demonstrating the potential clinical value of the manipulator for retinal microsurgery.