Finite Element Analysis and Structural Modification of Catheter-Type Tactile Sensor Based on Polyvinylidene Fluoride Film

To enable quantitative palpation in vivo, we previously developed a catheter-type tactile sensor that uses a polyvinylidene fluoride (PVDF) film for detecting lesions based on surface changes. This study investigates the effects of the structural parameters for the sensor on the piezoelectric output. A coupled electrical-structural finite element analysis (FEA) is used to simulate the displacement of a sensor tip composed of silicone rubber layers, a PVDF film, and a plastic substrate film. The FEA results indicated that encapsulating the plastic film in rubber increased the output charge by approximately 56.5%, primarily due to enhanced strain caused by lateral expansion of the silicone rubber. Increasing the plastic film thickness and the distance between the neutral plane and the PVDF film was also found to increase the output charge. In addition, the sensor output was larger when the lower rubber layer was made thicker than the upper rubber layer. However, the material used for the substrate film was predicted to have the dominant effect on the sensor output, with the largest output being achieved for a film with a large Young’s modulus. To confirm the FEA results, we fabricated prototype sensors that used plastic, steel, and titanium films, and experimentally evaluated their performance. The results indicated that an appropriate choice of film material could increase the sensor output by 18.9 fold.