ABSTRACT
Cellulose is the most abundant sustainable, inexpensive, biodegradable, people-safe polymer, present in well-known compounds that possess a broad range of properties. Some of these compounds are utilized in additive manufacturing (AM) as thickener, viscosity modifier, excipient, substrate, ingredient, binder, and cost reducer, and are cellulose acetate, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, and methyl cellulose. The chemistry, characteristics, commercial grades, producers, uses in and outside AM, and market of these compounds are elucidated in this chapter. Cellulose is present in numerous and very diverse feedstocks for AM but all of them are experimental and only one commercial. Many AM materials comprising cellulose are discussed: they remarkably cover applications ranging from plain substrate paper to electronic circuits for the Internet of Things, drug tablets, bone and tissue engineering, electrochemical capacitors, and constructions. Printed items containing cellulose also span orders of magnitude in size, from structural components made of concrete to microfluidic paper-based analytical devices. Uses of cellulose as an ingredient compatible with living cells are illustrated, along with new designs enabled by cellulose, such as biomimetic shape-changing articles.
Cellulose is versatile and compatible with either mainstream or advanced AM processes: laser sintering, extrusion-based, direct ink writing, 3D printing™, 4D printing, and glass-based extrusion. Such compatibility derives especially from the fact that cellulose is available in powder form, and lends itself to be incorporated in filaments, inks, and powders for AM. This chapter illustrates the many cases in which cellulose has been studied as a functional ingredient of biobased and non-biobased inks for AM, along with their benefits, such as improvement in printability and properties of printed items.
Cellulose can drive the diffusion of AM, if the performance/cost ratio of additively manufactured items with cellulose is attractive, and this ratio obviously hinges on material cost, and fabrication cost and rate. However, in some areas of cellulose application, such as medical, performance and customer satisfaction may be more critical than cost and worth paying a premium price for a product.
