Polymer 3D printing is an emerging technology with recent research translating towards increased use in industry, particularly in medical fields. Polymer printing is advantageous because it enables printing low-cost functional parts with diverse properties and capabilities. Here, we provide a review of recent research advances for polymer 3D printing by investigating research related to materials, processes, and design strategies for medical applications. Research in materials has led to the development of polymers with advantageous characteristics for mechanics and biocompatibility, with tuning of mechanical properties achieved by altering printing process parameters. Suitable polymer printing processes include extrusion, resin, and powder 3D printing, which enable directed material deposition for the design of advantageous and customized architectures. Design strategies, such as hierarchical distribution of materials, enable balancing of conflicting properties, such as mechanical and biological needs for tissue scaffolds. Further medical applications reviewed include safety equipment, dental implants, and drug delivery systems, with findings suggesting a need for improved design methods to navigate the complex decision space enabled by 3D printing. Further research across these areas will lead to continued improvement of 3D-printed design performance that is essential for advancing frontiers across engineering and medicine.

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The use of 3D printing for lattice structures has led to advances in diverse applications benefitting from mechanically efficient designs. 3D printed lattices are often used to carry loads, however, printing defects and inconsistencies potentially hinder performance. Here, we investigate the design, fabrication, mechanics, and reliability of lattices with repeating cubic unit cells using probabilistic analysis. Lattices were designed with 500µm diameter beams and unit cell lengths from 0.8mm to 1.6mm. Lattices were printed with stereolithography and had average beam diameters from 509µm to 622µm, thereby demonstrating a deviation from design intentions. Mechanical experiments were conducted to quantify the exponential increase in yield stress for the relative density of lattices that facilitated probabilistic failure analysis. Sensitivity analysis demonstrated performance was most sensitive to fluctuations in beam diameter (74%) and less to lattice yield stress (8%) for lattices with 1.6mm unit cells while lattices with smaller 1.0mm unit cells were most sensitive to yield stress (48%) and to beam diameter (43%) fluctuations. These findings provide new insights linking design, fabrication, mechanics, and reliability analysis for improved system design that is crucial for engineers to consider as 3D printing becomes more widely adopted.

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