A Novel 3-DOF Force Sensing Microneedle with Integrated Fiber Bragg Grating for Microsurgery

Retinal microsurgery requires precise manipulation of delicate tissue in the interior of the eye. Force sensing instruments can provide surgeons the imperceptible force information, thereby improving the safety of retinal microsurgery. Previous force sensing microneedles have demonstrated robust performance in transverse force measurement. However, in some surgical operations such as puncturing the vessel, the axial force sensing function is critical. In this study, we present a three degrees of freedom (DOF) force sensing microneedle based on fiber Bragg grating (FBG) sensors. A novel configuration of the FBG sensors is arranged to detect the transverse and axial forces. Three optical fibers with dual FBGs are longitudinally attached along the outside surface of a Nitinol tube. Benefiting from the novel configuration of the FBG sensors, a hollow channel can be used to pass through injection catheter. A new force calculation algorithm was developed to decouple the transverse forces and axial forces. Experimental results demonstrate the proposed force calculation algorithm can achieve a resolution of 0.124 and 0.74 mN for transverse forces and axial forces, respectively. Validation and temperature compensation experiments show the force sensor can provide consistent and accurate measurement of 3-D forces within 35 to 37 °C temperature variation.