Gillespie, Calum

English

Research in the field of soft robotics has looked to develop compliant devices which integrate methods of control and sensing into the body of the device. The aim of this PhD research is to reduce the need for traditional electrical componentry and increase the overall compliance of the robot. In this thesis the use of amorphous silicon (a-Si) as a functional material with electrostatic actuators is presented. The semiconductor properties of a-Si allow it to provide methods of optical activation of electrostatic actuators such as dielectric elastomer actuators (DEAs). In this work methods of fabricating a-Si are developed using a clean room facility to create solid state devices that can be used with soft robotic actuators. Various characterisation techniques have been explored including, scanning electron, atomic force microscopy and ellipsometry, to evaluate the fabrication process of a-Si. In addition, characterisation of the electrical and photonic properties of a Si are presented to help inform the electrical response of a-Si at high voltage as well as the design of optically controlled actuators. Initial development of an optically controlled dielectric elastomer actuator (DEA) using a-Si is presented and optical control of a DEA actuator with a voltage swing of 865V across the DEA was achieved from increasing light intensity, leading to recorded displacements of 2.2µm. It was also demonstrated that the optically controlled DEA showed repeatability in actuation as well as low latency of response. The optically controlled DEA was developed to generate larger displacements under different light intensities by exploiting unstable wrinkling of the DEA membrane. The onset of unstable wrinkling of a DEA design was investigated and used to develop an optically controlled DEA that has the potential to achieve larger displacement changes between ambient and illuminated states by transitioning between stable and unstable actuation. The use of this DEA membrane geometry allowed for increases in actuation of 16% between ambient and illuminated states. Although wrinkling of the optically controlled DEA was not observed due to saturation of the driver electronics output, predictions of the applied voltage range required to achieve this actuation window are presented. As well as opportunities for potential designs of active DEA windows and a DEA eye that could exploit the optical control methods presented. A compliant electrostatic zipping actuator that integrated a-Si as an active electrode was fabricated using thin film deposition of a-Si onto a flexible polyimide (Kapton) substrate. In contrast to the optically controlled DEA, the a-Si was fully embedded in the actuator structure. The a-Si zipping actuator showed a maximum change in curvature of 0.007mm-1 between ambient and illuminated lighting conditions. The compliant a-Si zipping actuator was shown to have increases in displacement of up to 300% in a simple harmonic oscillator conformation. The a-Si oscillator achieved larger change in displacement by exploiting changes in light intensity to move the simple harmonic oscillator from a low to high displacement mode. This thesis demonstrates the first steps in developing actuators that demonstrate novel methods of optical control of compliant actuators through the use of a-Si, reducing the need for conventional wired control systems.<br/

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Optical control of electrostatic actuators using amorphous silicon

https://research-information.bris.ac.uk/files/319322319/Final_Copy_2022_03_22_Gillespie_C_PhD_Redacted.pdf

Optical control of electrostatic actuators using amorphous silicon

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