Large-scale additive manufacturing with bioinspired cellulosic materials

Abstract

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.

Circular manufacturing of chitinous bio-composites via bioconversion of urban refuse

“…Here, FLAM was produced using the chitosan from the bioconversion of food waste reported above and cellulose from local waste (i.e., tissue paper and plant matter), and the latter was ground to achieve powder size of 200-500 µm. A stiff composite (E = 0.26 GPa) was obtained, with mechanical characteristics in the range of those of rigid polymer foams, metals foams, and softwoods 25 and similar to those reported for FLAMs of shrimp and plant origin 15 . Notably, despite the low mechanical differences between the bioconverted-chitosan-derived films and crustacean-derived chitosan films, such differences disappear when they are used to form FLAM.…”

“…Mechanical results obtained for the chitosan films offered encouraging evidence pertaining to their suitability for bioinspired chitinous manufacturing and their potential for widespread applications for producing strong composites and three-dimensional objects. Motivated by this success, its ability to form chitosan-cellulose bioinspired composites, also known as FLAMs, was investigated 15 . FLAMs, which mimic the composition of an oomycetal wall, are currently produced at costs similar to those of commodity plastics and ten times less than those of the cheapest plastic filaments used currently for additive manufacturing (i.e., 1.6$/kg, using 0.7$/kg wood pulp and 12$/kg chitosan).…”

“…Molecular characterization and imaging. The surface morphology of samples was examined using a Field Emission Scanning Electron Microscope (FESEM, JEOL, JSM-7600F) at 5 kV accelerating voltage, as previously reported 15 . Samples were gold-coated for 30 s while being mounted onto a carbon tape on an aluminum stub.…”

“…The values of K and α are taken from what was previously determined with identical setting as 0.74 ×10 −3 and 0.76, respectively.Mechanical testing. The mechanical properties of chitosan film and FLAM of insect chitin were evaluated by the tensile test performed using UTM (Universal Testing Machine-Instron 5943) equipped with 1 kN load cell with a cross head speed of 4 mm min −1 at ambient conditions according to the standard method (ASTM D1037-12) 15 . Chitosan films specimens were cut into strips with 70 mm length and 20 mm width.…”

“…Motivated by the ubiquity and mechanical relevance of chitonous polymers, from an early hypothesis some ten years ago 14 bioinspired chitinous composites developed rapidly towards general-purpose manufacturing by demonstrating their capability for producing large-scale objects, integrating with additive manufacturing, fabricating within limited energy requirements, retaining costs similar to commodity plastics 15 , and perhaps most critically, being able to maintain seamless integration with the ecological cycles of earth spanning from their renewable sourcing and biological composition to their natural biodegradation 16 . In this study, earlier results on bioinspired chitinous manufacturing of fungus-like adhesive materials (FLAM) are correlated to recent advances on large-scale urban bioconversion, effectively transforming the most abundant types of urban waste into materials for sustainable manufacturing.…”