Face masks are loose-fitting masks that cover the nose and mouth and have ear ties at the back of the head whereas respirators are tight-fitting face covering devices which filter the air during inhalation and exhalation. Guidelines issued by the US Centers for Disease Control and Prevention (CDC) regarding proper design, filtration process and wearing should be followed. The mask equipment provides protection against the infections caused by particulate matters (PM), especially PM2.5, and biological pathogens such as bacteria and viruses. Although face masks offer benefits to a greater extent, it is not recommended to wear them for a long period of time. As N95 masks closely fit with the face, it may result in negative impact on respiratory and dermal mechanisms of human thermoregulation. In this article, currently available face masks including cloth masks, their filtration mechanisms, manufacturing methods and decontamination methods are reviewed for the purpose of helping with the coronavirus pandemic (COVID-19).

Polylactic acid (PLA) and thermoplastic polyurethane (TPU) were mixed in different proportions and extruded through twin-screw and single-screw extruders to obtain composite filaments to be used for 3D printing with fused deposition modeling (FDM) method. The properties of the filaments were characterized using uniaxial tensile tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), rheology, polarized optical microscope (POM), and scanning electron microscope (SEM). 3D printed samples from composite filaments were tested using dynamic mechanical analysis (DMA). It was found that the tensile strength and modulus of the filaments decrease while elongation at break increases with the increasing TPU content in the composite. The analysis also showed a partial miscibility of the polymer constituents in the solution of composite filaments. Finally, a flexible structure, plain weave fabric, was designed and 3D printed using the composite filaments developed which proved that the filaments are well suited for 3D printing.

Fused Deposition Modeling (FDM) is a widely used 3D printing technique, which works based on the principle of melted polymer extrusion through nozzle(s) and depositing them on a build plate layer by layer. However, products manufactured with this method lack proper mechanical strength. In this work, 2/1 twill weave fabric structures are 3D printed using poly (lactic) acid (PLA). The ultimate tensile strength in the warp and weft directions and the modulus (stiffnesses) are measured for non-heat-treated (NHT) samples. The printed samples were heat-treated (HT) to improve the strength and stiffness. The variation in ultimate tensile strength is statistically insignificant in warp direction at all temperatures; however, the tensile strength in weft direction decreased after heat treatment. The modulus in warp direction increased by 31% after heat treatment while in the weft direction it decreased after heat treatment. Differential scanning calorimetry (DSC) tests showed the highest crystallinity at 125°C. The properties of the twill fabrics were compared with a standard dog-bone (DB) specimen using uniaxial tensile tests, Differential scanning calorimetry tests, and optical microscope (OM). For dog-bone specimens, the maximum values of crystallinity, ultimate tensile strength, and modulus were found to be at 125°C. The maximum crystallinity percentages are higher than that of the NHT samples. The ultimate tensile strength of NHT DB specimen 3D printed in horizontal orientation improved after heat treatment. The ultimate tensile strength of DB samples in vertical directions increased after heat treatment as well. The stiffness increased in both directions for DB samples.

Various types of additive manufacturing (AM) methods (also called 3D printing), and materials have been increasingly studied in the field of additive manufacturing of flexible structures such as fabrics, and flexible electronics. Polymer-based AM processes allow the flexibility, rapid, and low-cost fabrication of complex geometries depending on the types of materials used. The purpose of this review article is to summarize the major AM methods, materials, and their emerging applications to additively manufacture the flexible structures. In the AM methods section, Fused Deposition Modeling (FDM), and Selective Laser Sintering (SLS) are reviewed for fabrics, and Direct Ink Writing (DIW) for electronics. In the Materials section, the manufacturing methods, chemical structures, properties, advantages, and limitations of some of the widely used materials in three-dimensional (3D) printing of polymers are reviewed. Third, the applications of these methods and materials for fabrics, and electronics are covered. Finally, the associated opportunities and challenges in 3D printing process of flexible structures are described. The future research should be related to the exploration of combinations and development of innovative materials, printing process parameters, detail study on improving the properties, and hybrid 3D printing process.

The objective of this study is to manufacture composite filaments to be used in three-dimensional (3D) printing of fabrics using fused deposition modeling (FDM) method. The primary properties of a fabric are flexibility and strength which are lacking in the available 3D printed materials. Polylactic acid (PLA), thermoplastic polyurethane (TPU) and poly(ethylene) glycol (PEG) were blended in different proportions and extruded using twin-screw extruder to obtain composite filaments. The properties of the filaments were studied using various material characterization methods such as uniaxial tensile test, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). With the addition of PEG in the PLA/TPU composition, it was found that the yield stress and Young’s modulus of the composite filaments have significantly decreased compared to that of pure PLA filament. It was also noted that there was no significant difference in ultimate tensile strength whereas the elongation at break was increased by more than 500%. Using the composite filament, a plain weave fabric structure was 3D printed to investigate the printing ability of a complex structure. It is concluded that the composite filaments developed are suitable for 3D printing but non-uniformity in diameter affects the print quality and hence the overall properties of fabrics.