3-Dimensional alignment of micro components using liquid droplets

• Main Author: Overton, James
• Published: University of Nottingham 2017
• Subjects: 620.1; TS Manufactures
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.719632

This thesis presents an improved understanding of how liquid surface tension controls component alignment with a focus on factors associated with fabrication quality; offering insight into the impact of adopting the novel additive manufacturing route, and to provide means for designers and engineers, who are not intimately familiar with the dynamics of liquid alignment, to incorporate such features into their work. The work is supported by several novel models and methods created during the PhD project. The research objectives were addressed through a combination of experimental work, which established the feasibility of utilising additively manufactured binding sites for liquid droplet alignment tasks, and modelling using Surface Evolver, which simulated component alignment tasks and the effect of imperfect binding site geometry. Droplet shape on circular and square binding sites with varying edge geometry was investigated and significant increases in contact angle of liquid water droplets were observed compared to the plain substrate, with clear benefits observed for structures with actual edge geometries < 90° which achieved repeatable alignment with a mean final component misalignment of 31 µm and 14 µm standard deviation. Simulations showed that as edge radius of the binding site increased the ability to stop droplet motion around the edge diminished. For binding site undercut angles < 90° an energy penalty was observed which provided a barrier to droplet motion down the sidewall. For binding site angles > 90° an energy benefit was observed which encouraged droplet motion down the sidewall. The integration of Surface Evolver generated data into a commercial CAE package for the purpose of an optimisation design study was presented which highlighted the potential of the technique for analysing complex geometries which would otherwise be extremely difficult in Surface Evolver.