A Novel Shape Memory Polymer Actuator

Abstract

Bladder dysfunction, arising from an underactive bladder results in restricted mobility and the emergence of diseases such as kidney failure, with minimal long-term bladder treatments available. The developing field of Biorobotics presents solutions to problems of this nature by employing biomimetic principles and drawing from nature. In response to the propensity of the bladder to exhibit geometrical changes in the the long term, it is increasingly important to develop artificial tissues which closely mimic the mechanical and biological stimuli of natural muscle tissue. In this work, methods were employed to enable the design of shape memory composites that mimic the properties of the detrusor wall, amongst those properties were actuation. The shape fixity and shape recovery rates of silicone paraffin composites were analysed by heating them in a hot water bath measuring their change in elongation. The test results displayed a positive correlation between shape fixity and paraffin content. The results had also demonstrated that the specimens recovered almost entirely. Further, actuation was measured by clamping the specimens and measuring their contraction. Joule heating was employed as a method to thermally activate the shape memory behaviour of the silicone paraffin wax composites. Varying voltage as different responses were observed and image processing was used to extract the data. Ultimately the aim of the thesis is to provide a potential solution and prototype for a long term morphologically changing artificial detrusor. The findings in this study show promise in producing an artificial robotic detrusor that mimics the changing bladder shape while maintaining its fixity. Subsequently, the novel material composite which was investigated in this study may be used in wider shape memory polymer applications.