Force Measurement and Evaluation for Surgical Cutting Applications: Development of an Effective Characterisation Testbed

Sensorized instruments that cater for accurate measurement of the interaction forces (between biological tissue and instrument end-effector) during surgical procedures offer surgeons a greater sense of immersion during minimally invasive robotic surgery (MIRS). There is much ongoing research into force measurement/evaluation involving surgical graspers. However, comparatively little corresponding effort has been expended in the measurement and subsequent evaluation of forces between scissor blades and tissue. This paper presents the design and development of a force/strain measurement test apparatus, which will ultimately serve as an effective sensor characterisation and evaluation platform. Data acquired from the testing platform can be used to differentiate between tissue samples with differing mechanical properties in a reliable, repeatable manner. PVA cryogel samples which have been exposed to differing freeze-thaw cycles, giving properties similar to those of biological tissue are used. These samples, with a range of stiffness values, allow testbed performance to be evaluated over a wide range of tissue types. Further experimental data/analysis is presented which quantifies the levels of strain generated on the scissor blades during a cutting procedure. The resulting force/strain data correlates well with typical scissor cutting trends. This data is being used to establish a comprehensive set of operational requirements for force sensing transducers which could be incorporated into, or placed on to, a scissor blade end-effector. Future applications of the test equipment will include the assessment of new direct force sensing technologies for telerobotic end-effectors in minimally invasive robotic surgery