A medical tactile sensor for measuring tissue hardness in robotic surgical tools

We report a hardness sensor for non-intrusive characterization of tissue hardness in robotic surgical systems. The MEMS-based hardness sensor we developed is able to measure within a hardness range of 0.3 - 360psi based on normal contact, realizing excellent ability to distinguish certain biological samples. To our knowledge, such wide dynamic range and capability of bio-tissue recognition have not been experimentally demonstrated in the past. The `tandem spring´ design of the sensor is implemented using a novel direct silicon-PCB packaging scheme recently developed by our group. We also discovered that two underlying control parameters (θ and σ_r) determine the sensor´s performance. Further, we developed a 2-phase measurement scheme to achieve both wide range and high sensitivity for various hardness samples.