Date of Award
Master of Science
In this thesis work, electrically conductive CNF/PCL composite fibers were fabricated using the microfluidic method. The fibers were made with different content levels of CNFs and flow rate ratios between the core and sheath fluids. The electrical conductivity and tensile properties of these fibers were then investigated.
A cross-flow geometry microfluidic channel with four chevron-shaped grooves as shaping elements was designed for microfluidic fiber fabrication. A CNC micro-milling machine was used to create the PMMA master molds, the surfaces of which were further smoothened by chloroform vapor. PDMS microchannel was prepared by molding replication based on the micro-machined PMMA master molds.
Using the as-fabricated PDMS microchannel, electrically conductive CNF/PCL composite fibers were successfully fabricated using the microfluidic method. It was found that at a CNF concentration of 3 wt.%, the electrical conductivity of the composite fiber increased to 1.11 S/m, which was around 1015 times of the electrical conductivity of the pure PCL. The yield strength, Young’s Modulus and ultimate strength of the 3 wt.% CNF/PCL composite fiber increased relative to the pure PCL fiber by a factor of 1.72, 2.88, and 1.23, respectively. Further increasing the content of CNF, the electrical conductivity increased slightly, while the tensile strength dropped sharply due to the agglomeration of CNF. Additionally, the results showed that the microfluidic could be considered as an effective method to align CNFs along the fiber in the longitudinal direction. The alignment of the CNFs showed a positive effect on the electrical conductivity and tensile strength.
Lu, Mingchang, "Aligning carbon nanofibers in PCL microfibers using microfluidic method: An approach to efficiently improve electrical conductivity and mechanical strength" (2016). Graduate Theses and Dissertations. 15966.