Additive manufacturing (AM) (also known as 3D printing) has enabled the customized fabrication of objects with complex geometries and functionalities in mechanical and electrical properties. AM technologies commonly use polymers and composites and have been advancing in a variety of industrial and emerging applications. Despite recent progress in 3D printing of polymer composites, many challenges, such as the suboptimal quality of manufactured products and limited material available for 3D printing, need to be addressed for the broad adoption of additively manufactured polymer composites. This review first provides a brief history of AM technologies along with 3D printing polymers. Subsequently, we discuss the state-of-the-art for the design of polymers and filling materials, the principles of AM processes, and emerging applications of 3D printed polymer and composites. Finally, we share our outlook of potential problems and challenges presented in AM of polymer composites, which might lead to future research directions.

Polymers are widely studied materials with diverse properties and applications determined by molecular structures. It is essential to represent these structures clearly and explore the full space of achievable chemical designs. However, existing approaches cannot offer comprehensive design models for polymers because of their inherent scale and structural complexity. Here, a parametric, context-sensitive grammar designed specifically for polymers (PolyGrammar) is proposed. Using the symbolic hypergraph representation and 14 simple production rules, PolyGrammar can represent and generate all valid polyurethane structures. An algorithm is presented to translate any polyurethane structure from the popular Simplified Molecular-Input Line-entry System (SMILES) string format into the PolyGrammar representation. The representative power of PolyGrammar is tested by translating a dataset of over 600 polyurethane samples collected from the literature. Furthermore, it is shown that PolyGrammar can be easily extended to other copolymers and homopolymers. By offering a complete, explicit representation scheme and an explainable generative model with validity guarantees, PolyGrammar takes an essential step toward a more comprehensive and practical system for polymer discovery and exploration.As the first bridge between formal languages and chemistry, PolyGrammar also serves as a critical blueprint to inform the design of similar grammars for other chemistries, including organic and inorganic molecules.

Figure 1: Samples of knitted garments designed and customized with our tool, and fabricated on a wholegarment industrial knitting machine. (A) Various garment prototypes on a 12 inch mannequin; (B) a glove with lace patterns on its palms; (C) an infinity scarf with noisy lace patterns; and (D) a sock with a ribbed cuff.

No abstract

We present a novel workflow to design and program knitted garments for industrial whole-garment knitting machines. Inspired by traditional garment making based on cutting and sewing, we propose a sketch representation with additional annotations necessary to model the knitting process. Our system bypasses complex editing operations in 3D space, which allows us to achieve interactive editing of both the garment shape and its underlying time process. We provide control of the local knitting direction, the location of important course interfaces, as well as the placement of stitch irregularities that form seams in the final garment. After solving for the constrained knitting time process, the garment sketches are automatically segmented into a minimal set of simple regions that can be knitted using simple knitting procedures. Finally, our system optimizes a stitch graph hierarchically while providing control over the tradeoff between accuracy and simplicity. We showcase different garments created with our web interface.