Experimental study on the effects of dielectric layer thickness and elastic modulus on the performance of flexible capacitive sensor films

Abstract

A stenosed blood vessel with a calcified part has complex shape and deformation properties. When using a catheter device in the blood vessel, a large deformation occurs, so the sensor needs to be flexible, and film sensors are used for contact force and pressure measurements dur ing in vitro evaluations. Various flexible film sensors are available. However, capacitive sensors are widely used because of their simple structure and low power consump tion. When using a balloon catheter in a calcified vessel, wide range of contact pressure may act on blood vessels, such as poor contact (less than the order of 1 kPa) and stress concentration areas (more than the order of 100 kPa). In this study, the performance of a capacitive film sensor is investigated over a wide pressure range 1-1000 kPa by focusing on the thickness and elastic modulus of its dielec tric layer. The sensitivity of capacitance change is high for sensors with thin and soft dielectric layers. However, the sensor is considered to be more affected by creep deforma tion. The sensor can detect the contact pressure between the balloon catheter and the model vessel during balloon dilation. During the use of catheter devices through in vitro experi ments using flexible film sensors, quantitative mea surement of the load on blood vessels is useful for acquiring knowl edge for application in clinical device selection and mechan ical evaluation testing during new device development.