Graduate Studies
Embargoed Master's Theses
First Advisor
Yuris Dzenis
Committee Members
Jeffrey Shield, Jung Yul Lim
Date of this Version
8-2025
Document Type
Thesis
Citation
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Mechanical Engineering and Applied Mechanics
Under the supervision of Professor Yuris Dzenis
Lincoln, Nebraska, August 2025
Abstract
Continuous nanofibers (NFs) represent a unique class of nanomaterials with numerous advantages for a large number of applications. The recent discovery of concurrently high strength, stiffness, and toughness in ultrafine electrospun nanofibers has sparked significant interest in controlling fiber diameter. A considerable research effort has been dedicated to analyzing the effects of process parameters on diameter. However, uniform fabrication of ultrafine continuous nanofibers remains elusive. The objectives of this thesis were to explore further and study several new methods of controlled fabrication of nanofibers, their assemblies, and nanocomposites. The possibility of fiber diameter control by varying environmental factors has been analyzed. Nanofibers have been electrospun at different temperatures and relative humidities (RH). Evaluation showed that, unexpectedly, high RH increased fiber diameter for organic solvent-based systems. The vapor-induced phase separation mechanism of this unusual phenomenon has been proposed and verified. It was shown for the first time that solvent vapor-assisted electrospinning can lead to uniform, smooth ultrafine NFs. Additionally, a method for the controlled fabrication of large, aligned 3D nanofiber assemblies has been developed and demonstrated using a modified split electrode approach. The method is suitable for the continuous production of large nanofiber constructs with tunable NF density. A non-destructive optical evaluation of NF density has also been demonstrated. Finally, the possibility of integrating NFs with Digital Light Processing (DLP) polymer additive manufacturing and controlling the “writing” of NFs on substrates has been explored. DLP-produced nanocomposites exhibited significantly improved mechanical toughness. The results of this thesis can be used for controlled nanomanufacturing of strong and tough NFs, their 3D assemblies, and composites for various structural and functional applications.
Advisor: Yuris Dzenis
Comments
Copyright 2025, Emmanuel Kweku Mensah. Used by permission