Year: 2019
Type: dissertation
Abstract: In quest for new functional materials, cellulose nanocrystals (CNCs) have attracted great interest due to their sustainability, biocompatibility, ease of surface functionalization, and mechanical strength. In this thesis different hydrogels derived from CNCs for various applications have been developed. The hydrogels derived from CNC in this thesis can be divided into isotropic and anisotropic hydrogels. High capacity, low cost and sustainable materials for waste water treatment and heavy metal removal are in high demand. An isotropic nanocolloidal hydrogel based on CNCs and graphene quantum dots (GQDs) was developed. The microstructure, permeability and mechanical properties of the hydrogel was dependent on the concentration and the ratio of the two precursors. Microfluidic microgels have been used for heavy metal scavenging and wastewater treatment applications. Higher concentration of GQDs lead to higher adsorption capacity for different heavy metal ions. To study the possibility of alignment of CNCs in shear field, studying the kinetic of alignment and relaxation of alignment, an oscillatory microfluidic device was used. Higher frequency of oscillations led to higher alignments in different regions of the microchannel. An increase in the viscosity of the CNC suspension led to higher degree of alignment. At higher viscosities the relaxation of alignment was also slower. Similar to the morphology of the native tissue which contains unidirectionally aligned collagen fibers, anisotropic hydrogels that mimic the native tissue morphology are highly desired. Nanofibrillar hydrogel derived from CNCs and gelatin have been prepared to study the role of shear in fabrication of anisotropic hydrogels. Variation of concentration and ratio of hydrogel precursors led to various gelation times, permeability and mechanical properties. Using different printheads, sheets of CNC/gelatin hydrogels have been extruded and fluidic control in achieving composition gradient in transverse and longitudinal direction was explored. Variation in the substrate temperature was used to tune the degree of alignment in the hydrogel sheets. Hydrogels derived from CNC and Chitosan were developed to form a shear-thinning photo crosslinkable hydrogel for fabrication of personalized wound dressings. The structure, mechanical properties and swelling of the hydrogels were dependent on the concentration and ratio of the precursors. The hydrogels could be loaded with various active ingredients (AI) to add different functionalities. These functional hydrogels were printed in different shapes to program the release of AI in a controlled manner.
Source: TSpace (University of Toronto)
Author: Moien Alizadehgiashi
Language: English
Subfield: Biomaterials
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3214440301