Cellulose is the most abundant and broadly distributed organic compound and industrial by-product on Earth. However, despite decades of extensive research, the bottom-up use of cellulose to fabricate 3D objects is still plagued with problems that restrict its practical applications: derivatives with vast polluting effects, use in combination with plastics, lack of scalability and high production cost.
Here we demonstrate the general use of cellulose to manufacture large 3D objects. Our approach diverges from the common association of cellulose with green plants and it is inspired by the wall of the fungus-like oomycetes, which is reproduced introducing small amounts of chitin between cellulose fibers. The resulting fungal-like adhesive material(s) (FLAM) are strong, lightweight and inexpensive, and can be molded or processed using woodworking techniques. We believe this first large-scale additive manufacture with ubiquitous biological polymers will be the catalyst for the transition to environmentally benign and circular manufacturing models.
Cellulose and chitin are the first and second most abundant polymers on the surface of the Earth, and consequently a recurrent topic of research for their potential utilization in manufacture. Typically, cellulose is associated
with plants and chitin with arthropods, however, the natural occurrence of both biopolymers as structural components broadens to most kingdoms of eukaryota and bacteria. Despite their abundance, they rarely coappear in the same organism. One exception of this is certain species of oomycetes, a large class of eukaryotic organisms. Oomycetes grow in a mycelial form as fungi. However, in contrast to fungi which are characterized by a chitinous wall, oomycetes’ cell walls, and those of their close relative hyphochytrids, are predominately based on cellulose.
In the last few years, the pathogenic nature of some oomycetes has motivated a meticulous characterization of their wall singularities, as possible targets for disease control. Those studies have also shed some light on the characteristics of natural structures made of chitin and cellulose. This knowledge has a direct application in the development of bio-inspired materials. We now know oomycetes are not a homogeneous population but a combination of members with at least three distinctive cell wall types. While those walls are mostly composed of cellulose, they also contain low concentrations of chitinous polymers, comprising up to 10% of the cellulose. Inspired by this idea we studied the effects on manufacturability of cellulose by the addition of small amounts (<15%) of highly deacetylated chitin (i.e. chitosan) and the influence of the chitinous polymer in the ability of the composite to form three-dimensional structures.