Using Large-Scale Additive Manufacturing as a Bridge Manufacturing Process in Response to Shortages in Personal Protective Equipment during the COVID-19 Outbreak.

The global coronavirus disease (COVID)-19 pandemic has led to an international shortage of personal protective equipment (PPE), with traditional supply chains unable to cope with the significant demand leading to critical shortfalls. A number of open and crowdsourcing initiatives have sought to address this shortfall by producing equipment such as protective face shields using additive manufacturing techniques such as fused filament fabrication (FFF). This paper reports the process of designing and manufacturing protective face shields using large-scale additive manufacturing (LSAM) to produce the major thermoplastic components of the face shield. LSAM offers significant advantages over other additive manufacturing technologies in bridge manufacturing scenarios as a true transition between prototypes and mass production techniques such as injection molding. In the context of production of COVID-19 face shields, the ability to produce the optimized components in under 5 min compared to what would typically take 1 - 2 h using another additive manufacturing technologies meant that significant production volume could be achieved rapidly with minimal staffing.

Design and fabrication of 3-D printed conductive polymer structures for THz polarization control.

In this paper, we numerically and experimentally demonstrate the inverse polarization effect in three-dimensional (3-D) printed polarizers for the frequency range of 0.5 - 2.7 THz. The polarizers simply consist of 3-D printed strip lines of conductive polylactic acid (CPLA, Proto-Pasta) and do not require a substrate or any further metallic deposition. The experimental and numerical results show that the proposed structure acts as a broadband polarizer between the range of 0.3 THz to 2.7 THz, in which the inverse polarization effect is clearly seen for frequencies above 0.5 THz. In the inverse polarization effect, the transmission of the transverse electric (TE) component exceeds that of the TM component, in contrast to the behavior of a typical wire-grid polarizer. We show how the performance of the polarizers depends on the spacing and thickness of the CPLA structure; extinction ratios higher than 20 dB are achieved. This is the first report using CPLA to fabricate THz polarizers, demonstrating the potential of using conductive polymers to design THz components efficiently and robustly.

A microstereolithography resin based on thiol-ene chemistry: towards biocompatible 3D extracellular constructs for tissue engineering.

A new class of degradable aliphatic poly(carbonate) resins for use in microstereolithographic process is described. Using a biologically inert photo-inhibiting dye, exemplar 3-dimensional structures were produced using thiol-ene chemistry via microstereolithography. Fabricated constructs demonstrated good biological compatibility with cells and had tensile properties that render them suitable for use as tissue engineering scaffolds.

Fabrication of 3-dimensional cellular constructs via microstereolithography using a simple, three-component, poly(ethylene glycol) acrylate-based system.

A novel method for the production of inhibitor- and solvent-free resins suitable for three-dimensional (3D) microstereolithography is reported. Using an exemplar poly(ethylene glycol)-based resin, the control of features in the X, Y, and Z planes is demonstrated such that complex structures can be manufactured. Human mesenchymal stem cells cultured on the manufactured scaffolds remained viable during the 7 day assessment period, with proliferation rates comparable to those observed on tissue culture polystyrene. These data suggest that this novel, yet simple, method is suitable for the production of 3D scaffolds for tissue engineering and regenerative medicine applications.

A simple, low-cost conductive composite material for 3D printing of electronic sensors.

3D printing technology can produce complex objects directly from computer aided digital designs. The technology has traditionally been used by large companies to produce fit and form concept prototypes ('rapid prototyping') before production. In recent years however there has been a move to adopt the technology as full-scale manufacturing solution. The advent of low-cost, desktop 3D printers such as the RepRap and Fab@Home has meant a wider user base are now able to have access to desktop manufacturing platforms enabling them to produce highly customised products for personal use and sale. This uptake in usage has been coupled with a demand for printing technology and materials able to print functional elements such as electronic sensors. Here we present formulation of a simple conductive thermoplastic composite we term 'carbomorph' and demonstrate how it can be used in an unmodified low-cost 3D printer to print electronic sensors able to sense mechanical flexing and capacitance changes. We show how this capability can be used to produce custom sensing devices and user interface devices along with printed objects with embedded sensing capability. This advance in low-cost 3D printing with offer a new paradigm in the 3D printing field with printed sensors and electronics embedded inside 3D printed objects in a single build process without requiring complex or expensive materials incorporating additives such as carbon nanotubes.