The COVID-19 pandemic has disrupted the supply chain for personal protective equipment (PPE) for medical professionals, including N95-type respiratory protective masks. To address this shortage, many have looked to the agility and accessibility of additive manufacturing (AM) systems to provide a democratized, decentralized solution to producing respirators with equivalent protection for last-resort measures. However, there are concerns about the viability and safety in deploying this localized download, print, and wear strategy due to a lack of commensurate quality assurance processes. Many open-source respirator designs for AM indicate that they do not provide N95-equivalent protection (filtering 95% of SARS-CoV-2 particles) because they have either not passed aerosol generation tests or not been tested. Few studies have quantified particle transmission through respirator designs outside of the filter medium. This is concerning because several polymer-based AM processes produce porous parts, and inherent process variation between printers and materials also threaten the integrity of tolerances and seals within the printed respirator assembly. No study has isolated these failure mechanisms specifically for respirators. The goal of this paper is to measure particle transmission through printed respirators of different designs, materials, and AM processes. The authors compare the performance of printed respirators to N95 respirators and cloth masks. Respirators in this study printed using desktop- and industrial-scale fused filament fabrication processes and industrial-scale powder bed fusion processes were not sufficiently reliable for widespread distribution and local production of N95-type respiratory protection. Even while assuming a perfect seal between the respirator and the user’s face, although a few respirators provided >90% efficiency at the 100−300 nm particle range, almost all printed respirators provided <60% filtration efficiency. Post-processing procedures including cleaning, sealing surfaces, and reinforcing the filter cap seal generally improved performance, but the printed respirators showed similar performance to various cloth masks. The authors further explore the process-driven aspects leading to low filtration efficiency. Although the design/printer/material combination dictates the AM respirator performance, the identified failure modes originate from system-level constraints and are therefore generalizable across multiple AM processes. Quantifying the limitations of AM in producing N95-type respiratory protective masks advances understanding of AM systems toward the development of better part and machine designs to meet the needs of reliable, functional, end-use parts.

COVID-19 大流行扰乱了医疗专业人员个人防护设备 (PPE) 的供应链，包括 N95 型呼吸防护口罩。为了解决这种短缺问题，许多人希望增材制造 (AM) 系统具有灵活性和可访问性，以提供一种民主化、分散的解决方案，以生产具有等效保护措施的呼吸器。然而，由于缺乏相应的质量保证流程，人们担心部署这种本地化下载、打印和磨损策略的可行性和安全性。许多用于 AM 的开源呼吸器设计表明，它们不提供 N95 等效保护（过滤 95% 的 SARS-CoV-2 颗粒），因为它们要么未通过气溶胶生成测试，要么未经过测试。很少有研究量化通过过滤介质外的呼吸器设计的颗粒传输。这是令人担忧的，因为几种基于聚合物的 AM 工艺会产生多孔部件，并且打印机和材料之间的固有工艺差异也威胁到打印呼吸器组件内的公差和密封的完整性。没有研究专门针对呼吸器分离这些故障机制。本文的目标是通过不同设计、材料和 AM 工艺的印刷呼吸器测量粒子传输。作者将印刷口罩与 N95 口罩和布口罩的性能进行了比较。本研究中使用桌面和工业规模熔融长丝制造工艺以及工业规模粉末床熔融工艺打印的呼吸器对于 N95 型呼吸防护装置的广泛分布和本地生产不够可靠。即使假设呼吸器和用户面部之间有完美的密封，尽管少数呼吸器在 100-300 nm 粒子范围内提供了 >90% 的效率，但几乎所有印刷呼吸器的过滤效率都低于 60%。包括清洁、密封表面和加强过滤帽密封在内的后处理程序通常会提高性能，但印刷的呼吸器表现出与各种布口罩相似的性能。作者进一步探讨了导致低过滤效率的过程驱动方面。尽管设计/打印机/材料组合决定了 AM 呼吸器的性能，但已识别的故障模式源自系统级约束，因此可以在多个 AM 过程中推广。量化增材制造在生产 N95 型呼吸防护口罩方面的局限性，促进了对增材制造系统的理解，以开发更好的零件和机器设计，以满足可靠、功能性和最终用途零件的需求。