UBC Theses and Dissertations

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UBC Theses and Dissertations

Nanocellulose-based gel ionic conductors : design, manufacturing, and applications Ye, Yuhang


As the most promising candidate for replacing conventional rigid and brittle inorganic conductive materials, Gel ionic conductors (GICs) have piqued enormous interest in a wide range of fields. However, several limitations, including weak mechanical performance, low conductivity, narrow working temperature range, and proneness to dehydration, severely hinder their practical applications. In this thesis, I centered on leveraging cellulose nanofibrils (CNFs) to address these issues in combination with dedicated material design, innovative technology, and the validation of theoretical mechanisms. These nanocellulose-based gel materials were further assembled into diverse functional devices for proof-of-concept application. Especially, I first verified the addition of CNFs to GICs to improve both their mechanical properties and their ionic conductivity. Then extending this enhancement effect to ionogel system presents higher environmental resilience. To preserve the colloidal state of CNFs inside ionogels, a strategy of regulating the hydration interaction between CNFs, water, and ionic liquids was proposed resulting in a highly stretchable ionogel with environmental resilience. However, the sensitivity of strain sensors of these two GICs was not satisfactory. The system was further improved with enhanced sensitivity, where CNFs encapsulated and stabilized conductive fillers, overcoming the interfacial incompatibility between fillers, and surrounding hydrophilic polymer network. While these strategies improved performance there was a lack of robustness due to overlooking the fundamentals at the molecular level. From the molecular design perspective, we adopted CNFs and their hydrolysate (glucose) as patching materials to repair local and spatial imperfections of hydrogel networks, resulting in mechanically strong hydrogels with excellent dehydration resistance. This strategy is versatile and effective in varied material systems. Lastly, to better control the performance of GICs at macroscale, we developed a technique for patterning within hydrogels using CNF-based ink through 3D printing, enabling the tailoring of their mechanical properties while enhancing functionalities for advanced applications. Overall, the strategies presented in this thesis demonstrate the potential of CNFs in the fabrication of high-caliber ionic gel conductors for emerging applications.

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