Design and Modeling of Micro Tactile Sensor with Three Contact Tips for Self-Compensation of Contact Error in Soft Tissue Elasticity Measurement

The capability to localize diseased regions in soft tissues is essential in laparoscopic surgeries. Accordingly, surgeons need to use tactile feedback systems in order to evaluate tissue health. The purpose of this paper is to identify tissue stiffness using a new tactile sensor, whose output does not depend on the applied pushing distance or the contact angle between the sensor and the target tissue. A modification on the concept of using two linear springs with different stiffness is executed, where the current sensor design is based on using three linear springs. A detailed design procedure is carried out in order to achieve high linearity and sensitivity. The sensor measuring range is selected according to different soft-tissue properties. In order to verify the performance of the new design, a finite element model is constructed using the ANSYS software. The results illustrate that the presented sensor can distinguish between different tissues based on their modulus of elasticity, within the specified design range. Moreover, the sensor output is independent of the applied pushing distance and the contact angle, in the range of +/- 8 degrees, with a maximum error of +/- 4%. Furthermore, a linear I/O relationship was successfully achieved, which was the aim when considering nonlinearity analysis. (C) 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.