Cellulose nanocrystals (CNCs) are promising renewable nanoparticles with unique properties including high mechanical strength and a large aspect ratio. As such, CNCs easily form strong gels and networked structures. “Entangled” nanocellulose systems generally rely on physical cross-links, however, we have found that chemical cross-linking of CNCs with hydrazone bonds can extend the potential uses of these networked materials. CNCs orthogonally functionalized with hydrazide groups and aldehyde groups covalently cross-link when they come into contact. Cross-linked CNC aerogels possess some of the lowest reported densities to-date, are strong and flexible and do not disintegrate in liquid. These aerogels make extraordinary scaffolds and templates to support, absorb or release other chemicals and nanomaterials. We have previously shown cryo-templating of aerogels (i.e., critical point drying and freeze-drying) as one method to force CNCs into contact and create porous cross-linked materials, however, this presentation will demonstrate pressurized gas expansion technology and microfluidics as two new routes to assemble CNC aerogels. These processing methods are scalable and lead to less stiff aerogels with higher specific surface area and controllable shape. The droplet microfluidics approach produces cross-linked CNC aerogel microparticles (30-110 µm in diameter) that have predictable swelling and absorption properties and may find application as drug delivery or sorption agents, or as biodegradable beads for use in cosmetics and food. Furthermore, thin film CNC aerogels (3-85 µm thick) were patterned on a variety of substrates and can be used, for example, as electrolyte supports and templates in energy applications (e.g. photovoltaics or photoelectrochemical water splitting devices) or as cell culture arrays. Lastly, cross-linked cryo-templated CNC aerogels are demonstrated to be near-ideal scaffolds for bone regrowth where their flexibility effectively fills complex bone defects, their non-toxicity enables increased cell proliferation and healthy differentiation, and their mesopore morphology facilitates osteoconductivity as evidenced through in vitro and in vivo studies. Overall, CNC aerogels are promising “green” materials that can be further expanded by fine-tuning their properties and scaling-up their processing methods.

New processing and applications of cross-linked cellulose nanocrystal aerogels: Bone implants, delivery systems, and components for energy storage and production devices

2019 Spring National Meeting

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