Decoupling method solving axial/transverse forces crosstalk in retinal microsurgery´s force sensing instruments

Epiretinal membrane is a common disease of the eye which can cause severe loss of vision. Membrane peeling is the promising treatment in which surgeons use a miniature needle with a pick to peel off the membrane. However, due to the fragility of the retinal tissues and lack of force perception have made the procedure too risky to perform. Hence, development of smart tools/needles that use fiber Bragg grating (FBG) force sensors has been extensively reported. The main challenge was and yet is to decouple completely between axial and transverse forces. In this paper for the first time, we propose theoretically a novel method to decouple with high accuracy between the two force components. For the sake of holding out the method, only 2-DOF is considered here. Simulation was carried out to simulate 2-D needle integrated with two FBGs. One of which is a tapered FBG placed at the neutral axis of the needle for axial force measurement, while the second is normal FBG bonded on the needle´s surface to mind the lateral force. As the strain applied, the bandwidth of the FBGs is only analyzed. A mathematical model is developed to show how force vectors can be measured in reality.