Elasticity-Independent Angle Detection for Directional Palpation Using a Microfinger by Integrated Design of Flexible Strain Sensors

The sensor integration design, focusing on strain-to-angle conversion path of a strain sensor on a microfinger for detecting stiffness singularities in elastic objects, has enabled high-accuracy angular information independent of the target's elasticities. In our previous work, we integrated the strain sensor at the microfinger tip for indirect acquisition of the angle data. In the improved device, a stretchable strain sensor is integrated at the joint of the microfinger, enabling direct strain-to-angle conversion. The sensor was tested on a palpated object with elasticity variations. The accuracy (correlation coefficient) of the strain-to-angle conversion improved from 0.891 in the previous design to 0.997. This improvement can enhance the accuracy of tumor detection in laparoscopic surgery.