Dielectric Elastomer-based Multi-location Capacitive Sensor

Abstract

Dielectric Elastomers (DE) are a promising technology for sensing and actuation particularly well suited to diverse applications in soft robotics. Developing a sensor that can measure the force and location simultaneously could be useful for robotic and bio-instrument applications. This thesis describes the development of a DE based multi-location capacitive sensor techniques that have tactile sensory functions. The soft DE sensor developed in this work can measure pressure and multi-location contacts simultaneously. The sensor design is targeted at applications such as robotic fruit picking, a bio-instrument for the diabetic insole, etc. Modelling of DE sensors conducted in this work indicated that choosing the optimum substrate thickness that bonds the DE sensors to the rigid frame is an important to ensure DE sensors have sufficient sensitivity. Unique methods presented in this thesis, validated in simulated and experiments, overcome some of the limitations of the dielectric elastomer (DE) based sensor. A method is proposed to increase the sensitivity of DE force sensors using a flexible substrate and it is demonstrated how the finite element method (FEM) could be used for identifying the optimum substrate thickness for improved performance of compression sensors in specific applications, such as robotic grippers for picking hard and soft objects. This study explores the design of a compliant substrate and its influence on the contact mechanics and the effect of substrate thickness on the sensitivity of the dielectric elastomer capacitive sensors. Sensor with different substrate thicknesses were studied. The capacitance change also was investigated under a range of forces when indented with spherical objects of different stiffnesses ranging from hard metal to compliant fruit. A unique capacitance-based multi-location sensor designed to measure the pressure of any touch location is presented. This multimodal sensor is a soft, flexible, and stretchable dielectric elastomer (DE) capacitive pressure mat composed of a multi-layer soft and stretchy DE sensor. The top layer measures the applied pressure, while the underlying sensor array enables location identification. The sensor is placed on a passive elastomeric substrate to increase deformation and optimise the sensor's sensitivity. This DE multi-location capacitive sensor with pressure and localisation capability paves the way for further development with potential applications in bio-mechatronics technology and other humanoid devices.