Fiber drawing : beyond the scaling paradigm

Abstract

The emergence of multimaterial fibers that combine a multiplicity of solid materials with disparate electrical, optical, and mechanical properties into a single fiber presents new opportunities for extending fiber applications. Different functional fiber devices have been fabricated with a thermal co-draw approach. In order to make the thermal co-draw feasible, only materials with similar viscosity at the draw temperature are used, which excludes a wide range of metal and semiconductors that have good electrical property but not compatible viscosity profile. From the fiber structure point of view, the nature of the fiber drawing process makes fabricating a large quantity of fiber with identical inner structures feasible. The scalability of thermal drawing approach offers access to large quantities of devices however constrains the devices to be translational symmetric. Lifting this symmetry to create discrete devices in fibers will increase the utility of fiber devices. Also, the surface of the fiber is rarely studied though complex inner structure have been fabricated for different functionalities. Functionalize the fiber surface would give fiber the ability to better interact with the outer environment. This thesis seeks to address the abovementioned considerations, i.e. to expand materials selection for the fiber co-draw process and to explore variance of the fiber structure including breaking the inner structure translational symmetry and functionalize the outer surface. On the material side, a chemical reaction phenomenon is observed and studied in two different fiber drawing situations. In both cases, new composition is formed during the draw and play an important role in the formed fiber devices. On the structure side, relying on the principle of Plateau-Rayleigh instability, the fiber inner structure is designed to form a series of discrete semiconductor spheres contacting two metal buses after a thermal selective breakup process. This gives rise to photodecting devices in a silica-cladding fiber which shows a large working bandwidth. The fiber surface is also studied and successfully patterned with micron-scale features during the draw process. The formed patterned fiber surface shows potential in structural coloration and directional wetting.