Fig 1.
Distributed manufacturing and cotton candy machine for production of non-woven filtration media.
A: Distributed manufacturing paradigm allows for flexible, local production of material anywhere in the the world on short notice. B: Schematic illustration showing key steps of RJS process to produce non-woven fiber mats. C: Implementation of RJS using a retrofitted, commercially-available cotton candy machine. D-E: the process deposits fibers in a mat that can be collected and processed into filtration media. F: High speed camera footage showing ejection of material from the spinneret and onset of a Rayleigh-Taylor instability G-H: leading to the formation of nano- and microscale fibers from extrusion holes much larger in size(∼ 500 − 1000μm).
Fig 2.
Fiber processing and characterization.
A: Produced fibers must be processed into dense mats before they can be used as a filtration media. We evaluate two methods: i) calendaring and ii) compaction. Photographs show as-produced material (left) and material after compaction (right). B: SEM characterization of large-scale features of non-woven filtration media produced using Pinnacle 1112 PP homopolymer (MFI = 12 g/10 min). Insets show a macroscopic section of material obtained after each densification process compared with material obtained from a commercial N95 mask; scale bar represents to 1 cm. C: SEM characterization (top) enables comparison of fiber morphology between commercial N95 and fibers produced from using a modified CCM (image obtained from calendared sample shown in part B). Histograms (bottom) of fiber diameters show that both samples share a similar long-tailed distribution of fiber diameters. The black curve is a continuous probability distribution derived from the experimental data. Insets show the same distribution plotted on a logarithmic axis. Fiber diameters were measured from the sample at several different locations using 150 fiber counts.
Fig 3.
Performance of non-woven filtration media.
A: Filtration efficiency and B: pressure drop for several different materials produced via CMS plotted against the grammage of the sample. The numbers in the legend indicate the melt flow indices of the polymers. C: Phase plot of filtration efficiency vs pressure drop with marker size representing grammage of the sample. The markers represent mean reading from N ≥ 3 samples with a triplicate experiment for each sample. The error bars represent standard error of the mean on each side for both vertical and horizontal axes. The dashed lines represent the corresponding measurements for the filter material extracted from N95 FFRs. All the samples were prepared using 30g of polymer material except for those with explicitly mentioned values of 12g.
Fig 4.
Incorporation of locally sourced recycled material.
A: A distributed manufacturing framework enables incorporation of cycles within material life from raw polymer to dumping sites at landfills or oceans. Access to machines like the one presented in the study allows addition of value during recycling process, improving the chances of the material to be reused for multiple applications during its lifetime. B-E: Locally sourced waste polypropylene was cut into small pieces and combined with virgin 1112 PP resin at 1:5 ratio to produce fiber sheet. F-H: Light micrographs of thick fiber stems at 30x magnification. Phase separated droplets of waste material are visible inside as dark inclusion, which increase in number as we go from 20% (F) to 80% (H) proportion of recycled polymer. G-I: SEM characterization of the recycled-PP/PP hybrid showing unnoticeable variation in fiber morphology as we go from 20% (G) to 80% (I) proportion of recycled polymer.