A process for the development, characterization and correlation of composite materials for 3D printing is presented, alongside the processing of a polymer-ceramic functional composite using fused deposition modeling (FDM). The composite was developed using acrylonitrile butadiene styrene (ABS) as the matrix material filled with barium titanate (BT) micro-powder up to 35 vol % (74.2 wt %). The ABS-BT composites exhibited a shear thinning behavior with increasing ceramic content. The composite was 3D printed into structural and functional test samples using FDM by adapting and optimizing the print parameters. Structural characterization revealed increasingly brittle behavior at higher filler ratios, with the ultimate tensile strength falling from 25.5 MPa for pure ABS to 13.7 MPa for the ABS-35 vol % BT composite. Four-point flexural tests showed a similar decrease in flexural strength with increasing ceramic content. Functional characterization revealed an increase in the relative permittivity at 200 kHz from 3.08 for pure ABS to 11.5 for the composite with 35 vol % BT. These results were correlated with the Maxwell-Garnett and Jayasundere-Smith effective medium models. The process described in this work can be used for other 3D printing processes and provides a framework for the rapid prototyping of functional composites into functional parts with reliable properties. The ABS-BT composite shows promise as a functional dielectric material, with potential applications as capacitors and light-weight passive antennas.

The eruption of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (corona virus disease, COVID-19) in Wuhan, China, and its global spread has led to an exponentially growing number of infected patients, currently exceeding over 6.6 million and over 390,000 deaths as of the 5th of June 2020. In this pandemic situation, health systems have been put under stress, and the demand for personal protective equipment (PPE) exceeded the delivery capabilities of suppliers. To address this issue, 3D printing was identified as a possible solution to quickly produce PPE items such as face shields, mask straps, masks, valves, and ear savers. Around the world, companies, universities, research institutions, and private individuals/hobbyists stepped into the void, using their 3D printers to support hospitals, doctors, nursing homes, and even refugee camps by providing them with PPE. In Germany, the makervsvirus movement took up the challenge and connected thousands of end users, makers, companies, and logistic providers for the production and supply of face shields, protective masks, and ear savers. The Karlsruhe Institute of Technology (KIT) also joined the makervsvirus movement and used its facilities to print headbands for face shield assemblies and ear savers. Within this paper, the challenges and lessons learned from the quick ramp up of a research laboratory to a production site for medium-sized batches of PPE, the limitations in material supply, selection criteria for suitable models, quality measures, and future prospects are reported and conclusions drawn.

The present paper reports on the development of a biodegradable overmolded orthopedic implant: a metal bone fixing screw, which has been overmolded with a functionalized thin layer of biodegradable polymer to enhance cell adhesion during the healing process. The main challenges were to integrate precise, high-throughput and repeatable solutions to achieve a thin, defect-free structured polymer layer and to ensure a high and consistent implant quality. The work carried out entailed determining proper materials (Purasorb PDLG 5010) for the biodegradable overmolding layer and its economical substitute (NaKu PLA 100HF) to be used during initial tool and process development, designing the surface structure of the overmolded polymer layer, development of injection molding tools, as well as feeding and handling procedures. The injection overmolding process of Purasorb PDLG 5010 polymer was controlled, and the process parameters were optimized. In particular, the dominant process parameters for the overmolding, namely injection pressure, barrel temperature and mold temperature, were experimentally examined using a circumscribed three-factor central composite design and two quality marks; overmolding roughness and mass of polymer. The analysis of the experimental results shows that the mass of the overmolding is not feasible for use as the quality mark. However, the optimal parameters for the overmolding of a metallic implant screw with a thin, micro-structured polymer layer with a predefined roughness of the surface texture have been identified successfully.