Advances in 3-D printing: polymers, fabrication mechanisms, mass balance models and applications

Abstract In Science and Engineering, additive manufacturing, which is synonymously known as 3-D printing is a layer-by-layer computer-aided approach that is used to produce high precision commercial industrial products. So far, 3-D printing techniques, which translate computer-aided virtual 3-D models into physical objects, are gaining traction globally. However, the current evolution from conventional molding and machining to rapid prototyping followed by rapid additive manufacturing prompts new challenges for engineers and scientists alike. This review is particularly prompted by novel innovations in 3-D printing with respect to emerging fabrication designs and mechanisms, printable polymeric materials, and current applications. Central to all spotlights is the discussion on 3-D printing techniques discussed under 3 broad categories; (i) extrusion-based methods, (ii) powder binding technologies and (iii) photopolymerization methods and corresponding polymer design aspects, processing parameters and mass balance models. Aspects of mass-balance models addressed in this review include models of multimaterial 3-D printing of viscoelastic inks, Newtonian fluid in extrusion, the Gaussian Beam model and multiscale computational simulations for prediction of macroscale properties of various polymeric materials. This review also highlights selected applications that demonstrate how polymer-based 3-D printing is being exploited in industry, and future perspectives.