Estimating surgical needle deflection with printed strain gauges

The ability to track surgical needle deflection during procedures such as therapeutic drug delivery, biopsies, and medical device implantation allows clinicians to minimize positioning errors and procedural complications due to instrument deviations. We describe the use of a novel strain gauge printing method to sensorize surgical needles for the purpose of sensing needle shape and deflection during surgical procedures. The additive vapor-deposition based sensor fabrication method used here is capable of applying strain gauges (and resistive circuit elements) with micron-scale features onto surgical instruments of varying curvature and material composition without the need for mechanical machining. This fabrication method is used to apply several strain gauges onto an 18 gauge core biopsy needle to sense deflections. Validation experiments demonstrate a gauge factor of 1.16 for the printed strain gauges and nominal needle deflection measurement resolution of 500 microns.