UBC Theses and Dissertations

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UBC Theses and Dissertations

Soft capacitive force sensing skin : characterization, operation on a curved surface, and increased force range Morton, Kieran


Modern advances in medical robotics have brought them into many facets of day to day life, often directly interacting with humans. Some key applications of these robotics are human-interactive nursing robots and active prosthetics, where artificial ‘e-skins’ provide a soft interface with the environment. This thesis presents an investigation of long-term conductance stability for a flexible, stretchable conductive material, as well as two significant developments to a previously established flexible and stretchable combined pressure and shear sensor. The conductivity investigation was successful in reducing the resistance of flexible conductive elements by an order of magnitude, to approximately 1.8 kΩ. The two sensor development branches are aimed at creating a sensor that better resembles human skin in both form and function. Both sensors use a capacitive sensing approach to detect both pressure and shear using low-cost materials. The first area of development is exchanging the previously rigid and inflexible sensor base with a novel flexible one to allow for sensor function on surfaces with radii of curvature between 10 mm-100 mm, and updating the sensor characterization setup to accommodate curved devices. This work was successful in developing a sensor with a functional range of 0.1 N-1.6 N of normal force and 0-0.8 mm shear displacement at radii of curvature from 100 mm to 10 mm. The second is a novel sensor dielectric design which increases the functional range of the sensor to operate from a minimum functioning force of 0.05 N to a maximum functioning force of 50 N. This range increase is accomplished using a two-stage dielectric pillar shape, allowing the low normal force pressure and shear sensitivity of the original sensor design to be preserved while increasing the maximum allowable force significantly. Next steps in sensor design are integrating the high-force and flex designs, creating array-format sensors, and testing the device in practical environments such as basic robotic hands.

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