Browsing by Author "Huan, Siqi, Dr., Aalto University, Finland"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Structuring of Nanocelluloses in 3-D Functional Materials
    (Aalto University, 2022) Ajdary, Rubina; Rojas, Orlando, Prof., Aalto University, Finland; Huan, Siqi, Dr., Aalto University, Finland; Tardy, Blaise L., Dr., Aalto University, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Biobased Colloids and Materials; Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    This thesis investigates fundamental and practical aspects of the materials and methods used to assemble 3D structures from bio-based materials using mono- to multi-component systems through bottom-up and other processes. Fused Deposition Molding (FDM) and Direct Ink Writing (DIW) were used to fabricate structures with controlled geometries and properties. Nanocellulose from both microorganisms and wood featured promising biocompatibility and was investigated as primary subjects for the studies. We discuss the rheological requirements to process hydrogels by direct ink writing and address the effect of compositions and water interactions in the swelling of 3D-printed materials. The essential factors associated with cellular activities in biomedical applications were considered. The shear-thinning behavior of nanocellulose hydrogels facilitated the printability of the inks into defined shapes, which were investigated by using a wide range of needle sizes, lengths, and profiles. We discuss the effect of printing parameters and post-processing techniques on structural fidelity and properties. The nanocellulose-based mono and multi-component functional structures presented the advantages of inexpensive and fast production, dimensional retention and stability, ease of drying and rewetting process, thus facilitating packaging, transportation, and material sterilization while displaying excellent compatibility with cells. Material characterizations (for example, morphology, microstructure, mechanical performance, shrinkage, swelling, and degradation) were studied to define suitable applications for the developed structures. Our findings in this thesis are expected to facilitate future work to address standing challenges in constructing 3-dimensional bio-based materials.
  • Thumbnail Image
    Item
    Wet-spinning of cellulose nanofibril hydrogels
    (Aalto University, 2018) Lundahl, Meri; Rojo, Ester, Dr., Aalto University, Finland; Arboleda, Julio, Dr., Aalto University, Finland; Cunha, Gisela, Dr., Aalto University, Finland; Ago, Mariko, Dr., Aalto University, Finland; Huan, Siqi, Dr., Aalto University, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Biobased Colloids and Materials; Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Filaments were produced from cellulose nanofibrils (CNF) through wet-spinning for developments toward renewable fibre-based materials, such as absorbents or fibre-reinforced composites. The possibility to spin long filaments (i.e., spinnability) and resulting filament quality were related with the rheological behaviour of the CNF hydrogels used as precursors. A prototype wet-spinning line was developed for high-throughput filament production by co-extrusion with a supporting biopolymer shell around the CNF core. This system was also employed to spin absorbent filaments from CNF in combination with a shell that had limited compatibility with cellulose and coagulated effectively in aqueous media. The moisture sorption capacity was also increased by increasing the CNF surface charge, which also enhanced fibril alignment during filament formation. Filament mechanical integrity in wet conditions was improved through hydrophobic coating and interfibrillar crosslinking. The results highlight the use of wet-spinning as a simple and versatile approach to generate tuneable filaments from cellulose, an abundant bioresource. This will eventually enable the adoption of renewable options in applications that currently rely on fibres made from fossil carbon.