;Chapter 1 UV-resistant Self-healing Emulsion Glass as a New Liquid-like Solid Material for 3D Printing. Directly writing 3D structures into supporting mediums is a relatively new developing technology in additive manufacturing. In this work, durable and recyclable liquid-like solid (LLS) materials are developed as supporting mediums that are stable for both UV- and thermal-solidification. Our LLS material is comprised of densely packed oil droplets in a continuous aqueous medium, known as emulsion glass. Its elastic nature emerges from the jammed structure of oil droplets, which offers this LLS material rapidly self-healing ability. Moreover, the yield stress of the glass is relatively low and can be tuned by the viscosity and weight percentage of oil. The capability of the emulsion glass as supporting mediums is successfully demonstrated by directly writing and then curing designed structures. The emulsion glass has been repeatedly used at least 6 times upon exposure to UV irradiation and heat, implying it can expand the applications of supporting medium to the writing process involving UV- and thermal-curable inks simultaneously.
Chapter 2 In the second part, we changed the preparing procedures and the ratio of oil/water/surfactant in emulsions. Two emulsion systems formed by low-energy phase inversion methods are studied. The oil phase is decane while the surfactant is Tween 80 and Span 80 for system 1 and Dioctyl sulfosuccinate sodium salt (AOT) for system 2. With increasing the water content, the sample transited from liquid-like water-in-oil (W/O) emulsion to solid-like oil-in-water (O/W) emulsion. Eventually, liquid-like O/W emulsion was obtained as the amount of water is higher than 60wt%. The thermodynamic stability of solid-like O/W emulsion were confirmed by different preparation methods and long-term observation, it can be classified to be microemulsions. We also found that the viscoelastic property of the solid-like emulsions can be tuned by varying hydrophilic-lipophilic balance (HLB) and water content.
