Tip Tracking of Surgical Navigation Stylets Using Integrated Strain Sensors

During surgical procedures where navigation stylets are used to place surgical tools, the stylets are tracked as a rigid entity. However, when body tissue applies force to the stylet tip, the stylet bends and the tip location is lost. Tracking the stylet's bending and tip displacement can enhance the precision of surgical procedures such as catheter placement for external ventricular drainage. In this work, a flexible strain sensor is integrated at the base of a 1.3 mm diameter surgical navigation stylet. The device tracks the stylet's bending and tip displacement in two orthogonal directions. Thin-film silver strain gauges are patterned on polydimethylsiloxane (PDMS). The device is then wrapped around and adhered to a stylet using a silicone gel and acrylic adhesive stack. Using a cantilever beam model to fit the stylet deflection, the device's measurable tip displacement range is between 1 and 11 mm with a limit of detection of 750 μm.