Recently, significant developments in the formation of greener materials has revolved around the deconstruction of raw biomass into nano-scaled building blocks. In such a process, nanofibrils can be obtained in large quantities from agro-industrial waste streams and from the pulp and paper industries. Because of their outstanding mechanical properties and green source, the extracted fibrils of cellulose, so-called nanocellulose, bear a huge potential to revolutionize the formation of materials. In current research efforts, these bio-based nanomaterials have shown great promise in forming high performance materials, with the potential to replace plastics.
Besides the replacement of hazardous synthetic materials such as single use, disposable, materials, these biomaterials are evaluated towards high performance applications. For instance for their use in car parts, 3D-printable bioinks, reflective coatings, adhesives, high strength filaments, and many more.
An extremely enticing aspect of these bio-based nanoparticles is that they offer the promise of large-scale nanomanufacturing using water-based systems. Using water as the solvent to assemble these fibers results in a myriad of material types, with increasingly versatile properties as associated with ongoing worldwide nanomaterials research and developments.
Deconstruction of plants to form nanoparticles as a promising route for the bottom-up manufacturing of sustainable materials. Image: Luiz Greca / Aalto University
While high performance from nanoparticles is regularly demonstrated in scientific literature, the wonders associated with these progresses regularly remains limited to the bench due to toxicological concerns or poor manufacturability. Anytime a material is created from particles, one has to first come up with a way to assemble them, for instance, into a functional material. This is most commonly achieved through strategies that generate cohesion into the assembly. However, such strategies have been very particle dependent.
In a recent effort, a team led by Aalto University has shown another remarkable property of nanocelluloses: their strong binding properties to form new materials when compounded with virtually any nano- or microparticle.
The ability to keep things together is inherent to these nanofibrils, whether at the scale of nanoparticles or into large construction sites. They can act as mortar to a nearly infinite type of particles as described in the study. The ability of nanocelluloses to bring together particles into cohesive materials is at the root of the study that brings decades of research into nanoscience a step closer to actual manufacturing.
A scanning electron micrograph shows a fishnet structure formed by nanocellulose that has bound 1.15 micrometers silica particles together. Photo: Bruno Mattos / Aalto University
The study demonstrates how nanocellulose can organize itself in a multitude of different ways as a function of the other nano- and microparticles morphology and surface energy. This means that nanocelluloses induce high cohesion in particulate materials in a constant and controlled manner for all particle types. Because of such strong binding properties, such materials can now be built with predictable properties and therefore easily engineered.
Nanocelluloses bind micrometric particles, forming sheet-like structures, much like the paper-mâché done in schools. Nanocellulose can also form tiny fishnets to entrap smaller, nanoparticles. Using nanocellulose, materials built from particles can be formed into any shape using an extremely easy and spontaneous process that only needs water. Importantly, the study describes how these nanofibers form networks that follow precise scaling laws that facilitate their practical implementation.
This development is especially timely in the era of nanotechnologies, where combining nanoparticles in larger structures is essential. New property limits and new functionalities are regularly showcased at the nanoscale, but implementation in the real world is rare. Unraveling the physics associated with the scaling of the cohesion of nanofibers is therefore a very exciting first step towards connecting laboratory findings with current manufacturing practices. For any success, strong binding among the particles is needed, an opportunity offered by nanocellulose.
A scanning electron micrograph shows a paper-mâché structure formed by nanocellulose that has bound ~40 micrometers silica particles together. Photo: Bruno Mattos / Aalto University
The team has shown a pathway to achieve scalability in the production of materials, from particles as small as 20 nm in diameter to those that are 2000 times larger. Furthermore, inert particles such as metallic nanoparticles to living entities such as baker’s yeast can be compounded. They can be of different shape, from 1D to 3D, hydrophilic or hydrophobic. They can comprise living microorganisms, functional metallic particles, or pollen, achieving new combinations and functionalities. This is a powerful and generic method, a new alternative that bridges colloidal science, material development and manufacturing.
Nanoscience has been put forward as a key to enable higher performance and new functionalities in a wide range of applications. For nanoparticles extracted from plants with no or minimum additional chemical treatments, their safety clearance, including approval as food additives, can be facilitated. Therefore, as the field of nanotechnology is moving forward, integrating the use of green, bio-based, nanoparticles will become increasingly useful. This will be particularly true for materials with a short service lifetime such as packaging, single use personal protective equipment, or disposable filters. As such, finding ways to facilitate nanomanufacturing will become as important as the development of these outstanding nanoparticles, which are essential for future developments in materials science.
I am currently a research fellow in the bio-based colloids and materials research group at the Aalto University in Finland.
I obtained my M.Sc. in bioengineering from the Swiss Federal Institute of Science and Technology (EPFL), Switzerland (2009), and my Ph.D. in chemical and biomolecular engineering from the University of Melbourne, Australia (2015).
My research interests include the formation of structured materials from nano- and microparticles. My focus is to establish the physics of their interactions to facilitate their implementation into high performance sustainable materials.
The research into nanomanufacturing discussed in this opinion piece, is a result of work with Dr. Bruno Mattos and Prof. Orlando Rojas. Our interest is to couple the engineering of plants’ components, obtained from widely available streams, to address current sustainability challenges.
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