The Synthesis and Characterisation of Photoactive Materials and Their Use in Fluidic Transport Systems

The controlled movement of droplets through another immiscible liquid has the potential to impact on a diverse range of applications, from the study of biological and fluidic chemical transport to microreactor development and localised chemical reactions. Based on the Marangoni effect, control of motion can be realised by creating tension gradients through the external stimuli such as chemical, temperature and light. Among all the manipulation methods, light control is flexible and contactless and can be easily realised by using photoactive materials either in the external environment or in the droplet itself. Reports of the use of photoactive materials in the external environment to create gradients have shown limited control of droplet motion. The use of photoactive materials in the droplet had the potential to be a promising way to realise better control. However, it has scarcely been reported due to the difficulty in finding appropriate photoactive materials for the construction of such motion systems. This dissertation focused on the synthesis and characterisation of photoactive materials and their application in photocontrolled droplet motion systems. The photoactive materials mostly used in this thesis were based on spiropyran/merocyanine photoisomers. However, throughout the study, other materials like phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 2-nitrobenzaldehyde were also found to be applicable, opening a wider field of the research. Depending on the solubility of the photoactive materials, two types of droplet motion systems, that is, organic droplets in water (oil-in-water) and water droplets in organic medium (water-in-oil), were developed...