A sub-millimetric, 0.25 mN resolution fully integrated fiber-optic force-sensing tool for retinal microsurgery

Purpose Retinal microsurgery requires extremely delicate manipulation of retinal tissue where tool-to-tissue interaction forces are usually below the threshold of human perception. Creating a force-sensing surgical instrument that measures the forces directly at the tool tip poses great challenges due to the interactions between the tool shaft and the sclerotomy opening. Methods We present the design and analysis of a force measurement device that senses distal forces interior to the sclera using 1-cm long, 160 mu m diameter Fiber Bragg Grating (FBG) strain sensors embedded in a 0.5 mm diameter tool shaft. Additionally, we provide an algorithm developed to cancel the influence of environmental temperature fluctuations. Results The force-sensing prototype measures forces with a resolution of 0.25 mN in 2 DOF while being insensitive to temperature. Conclusion Sub-millinewton resolution force sensors integrated into microsurgical instruments are feasible and have potential applications in both robotic and freehand microsurgery.