Sub-millinewton force sensor for Vitreoretinal microsurgery using linear chirp fiber Bragg grating

A Vitreoretinal microsurgery force sensing technology has been rapidly emerging as the extremely small and delicate tissue structures of the eye interior dictates a precise and sensibly manipulation. Excessive applied forces during tool-tissue interaction manipulation lead to irreversible tissue damage. Fiber Bragg grating (FBG) based sensors are an excellent candidate as they meet all the constraints required by the retinal microsurgies; by being small size, provides sub-millinewton resolution, covering working range, etc. Significant progress leads researchers to move up from 1-DOF force sensor to 2-DOF and lately a 3-DOF that can measure tri-axis forces of mN scale in very restricted dimensions. Decoupling completely between the axial and transverse force components was the most challenge that could result in errors and less accuracy. In this study, we propose a linear chirp FBG (LCFBG) to be located in the middle of the device for axial measurement. Instead of commonly wavelength shifted decoding; we rather would retrieve applied forces using optical power measurement of the reflected peak of centre wavelength. A Simulation results using Matlab have showed linear relationship with adequate sensitivity around 6.8dB/N (0.0068dB/mN), and a resolution of <;0.6 mN was feasible. To promote the idea into reality we are in the process of exploring the designing conceptual that can induce gradual strain along the LCFBG to achieve the simplicity.