Proc. of 2014 IEEE 5th International Conference on Photonics (ICP), Kuala Lumpur, 2-4 Sept. 2014
Sub-Millinewton Force Sensor for Vitreoretinal Microsurgery using Linear Chirp Fiber Bragg Grating Abdulfatah A. G. Abushagur, A. Ashrif A. Bakar, Norhana Arsad, Sahbudin Shaari Department of Electrical, Electronics and System Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, UKM, 43600 Bangi, Selangor,
[email protected] has been developed. The sensor was mounted on the handle of the instrument 40 mm distal from the tool tip. The results have showed that the forces exerted during several tasks were higher than the investigation of [2]. Due to the small size of the instruments and the sub-mN resolution requirements represent the main challenges and make the above mentioned non-applicable in vitreoretinal microsurgies. Furthermore, the confound between frictions within the instruments and forces exerted due to the interaction between tool shaft and sclerotomy opening dictates the location of the force segment must be inside the eye. This enabled direct force measurement at the tool tip. Consequently, that has led the researchers to make use of optical fiber sensors, rather than the conventional strain gauges. The inherent advantageous properties of optical fibres, such as the small size, immunity to the electromagnetic interference (EMI), biocompatibility, non-toxicity and chemical inertness, allow them to be an ideal alternative tactile sensor [11]. Various force-sensing schemes utilizing fiber optic sensors either with Fabry-Perot interferometer [12], [13], light intensity modulation (LIM) [14], [15], or fiber Bragg grating [16]–[18] have been investigated in microsurgery and minimal invasive surgery (MIS). For MIRS, a 5 mm diameter tri-axial micro force sensor incorporating three optical fibers LIM has been developed [14]. Reference [13] was the first to develop a 3-DOF force sensing to measure the tri-axis force components in retinal microsurgery using FPI technique. Despite low cost of the LIM and high resolution of FPI techniques, power fluctuations in LIM and phase discontinuity in FPI have limited their use in retinal microsurgery. Finally using FBG technique, 1-DOF optical force sensor was developed by [16] to measure one axis force components with a resolution of 0.25 mN, an extensive survey on the advances in bio-tactile force sensors that can be applied in the field of MIS and microsurgeries using FBG technique was carried out by [19]. Recently a research group at Johns Hopkins University has been widely investigatign a force sensor instrumented using FBG technique for vitreoretinal microsurgical [1], [16], [20]– [23]. The main challenge in designing such extremely small devices was the confound signal between the transverse and axial forces. The contribution of the axial force onto the transverse forces has led them to develop an algorithm that
Abstract—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 3DOF 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
