Polymer nanocomposites in additive manufacturing processes for typical applications in the industry

Abstract Additive manufacturing (AM), commonly known as three-dimensional (3D) printing, is a widely used methodology that permits to fabricate fully customizable parts and objects with an astonishing level of geometrical complexity in a reduced time and with low costs. Polymers are, by far, the most widely used materials to fabricate 3D-printed parts due to its versatility and adaptability to many different environments or situations. The polymers used for AM could be used as carriers (or matrices) for nanocomposites of different nature. As a result, these composites could be used in a myriad of research and industrial fields such as aeronautics, automotive, architecture, energy supplies, food storage, optical, magnetical, microfluidic, and biomedical areas, among others. In this chapter, first, we briefly describe the working principle of AM and how is it possible to improve the performance of the fabricated parts via the inclusion of different types of nanochargers to produce nanocomposites. To do this, we will also summarize in an organized fashion, the multiple applications of 3D-printed nanocomposites focusing on innovative developments including the preparation of high strength materials, piezoelectric composites, optical devices, elastic materials or mechanochromic devices, among others. Moreover, we will also include one of the most innovative and recent advances in AM methodologies. For instance, four-dimensional printing, which corresponds to the design and fabrication of 3D-printed structures that have the capacity of changing their shape according to some external stimulus. This methodology opens the gate to several novel applications that were previously unthinkable in 3D printing. The addition of nanocomposites to these smart polymers, in several cases, constitutes an enhancement of their shape memory capacity, allowing the researchers to create optimized parts for several applications.