Multiscale Manipulation of Nanocellulose Structures for Divers Sustainable Materials

Thesis (Ph.D.)--University of Washington, 2021Global dependence on petroleum, a finite source, is creating economic, social, and environmental unrest. The quickly depleting limited resource needs a sustainable alternative that can offer the same multifunctional benefits as petroleum. Nanocellulose, or cellulose that is approximately 2 nm in diameter with varying lengths, is sourced from renewable forms of biomass including trees and grasses. Nanocellulose is a promising sustainable alternative, but in its current applications it lacks the adaptability to fill both basic and complex functionalities and thus fails to compete with petroleum products. However, controlling the structure of nanocellulose at multiple scales offers multiple points of control increasing its potential success in basic applications such as textiles and complex applications such as small electronics, sensors, or other biomedical applications. In this work we demonstrate the massive untapped potential of nanocellulose as a diverse sustainable alternative material to petroleum. Initially we demonstrate the multiple points of control available with nanocellulose production to tailor fiber aspect ratio and surface charge, giving independent control over two critical fiber properties. The individual control over theseproperties opens nanocellulose fibers to a wide range of applications not previously afforded by typical synthesis methods. Through these tailored properties we successfully designed nanocellulose for high performance in a novel pre-alignment technique involving electric field and flow focusing. The electric field provides individual CNF fiber rotation and a higher degree of alignment while the flow focusing provides a quick fiber fixation establishing permanent anisotropy. We demonstrate the positive effects of this alignment on mechanical performance and the potential of this continuous filament as an alternative textile. Finally, we further adapt this aligned filament to fill more complex applications by introducing a conductive filler to create an aligned conductive composite filament. While most report performance loss, through engineering the CNF nanostructure and carefully controlling the alignment of the composite components, we demonstrate exceptional performance beyond the qualities possible with a pure CNF filament. The alignment not only improves the mechanical properties but the electrical properties as well. The implications of this new conductive composite filament to fill complex functionalities are demonstrated through its performance as a micro wire for small electronics and a unique water sensor. This project demonstrates the potential of nanocellulose as a multifunctional and sustainably sourced alternative to petroleum