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3D printed and electrospun
mask with high filtration efficiency, the thickness nanofibers; and (3) it is not possible to change such
of the filter has to be increased due to its microsized filter, so the mask can only be disposable.
fiber diameter and large pore size . The thickness Recently, three-dimensional (3D) printing
[5]
of the mask can cause difficulty to breathe through, technology is introduced to easily integrate
and as a result, the wearer will inhale unfiltered nanofibers with 3D printed parts to support
air through the edge of the mask. In comparison nanofibers. In the literature, fused deposition
with melt-blown fibers, electrospun nanofiber web modeling (FDM) is the most common 3D
is an alternative candidate as a filtration media printing technology to be combined with
because of their small pore size, small diameter electrospinning [9-11] . In all these studies, the
and large specific surface area. Liu et al. electrospun nanofibers were directly deposited
[6]
prepared polyacrylonitrile (PAN)/polyacrylic acid onto the 3D printed objects. However, Kozior
composites nanofiber membranes as the filtration et al. pointed out that the adhesion between
[12]
medium and it had a removal efficiency (99.994%) the polylactic acid (PLA) printed objects and the
against the 300-500 nm NaCl aerosol particles PAN electrospun nanofibers was low. It could be
at an airflow velocity of 5.3 cm/s. Zhang et al. better when soft TPU was used as the collecting
[7]
reported the use of PSU/PAN/PA-6 hybrid fibrous substrate. To improve the adhesion between the
membranes to capture airborne particles and it nanofiber mat and the 3D printed object, the
can almost completely remove ~300 nm particles same research group proposed another reverse
[13]
with an extremely small pore size of 270 nm. method. They directly introduced 3D printed
Most of the studies investigated the air filtration PLA on the electrospun PAN nanofiber mats,
performance with 300 nm aerosol particles that and it was found that the adhesion between the
are slightly bigger than the viruses. Although there nanofibers and the printed polymer was stronger
is no direct measurement reported so far, we can than the connection among the nanofibers within
still conclude that nanofibers are extremely good the nanofiber mat. However, as the nanofiber mat
at capturing bigger airborne virions. Furthermore, had glued onto the printing bed before printing, it
severe acute respiratory syndrome-CoV-2 virus is is difficult to detach the composite, which is a big
usually transmitted by large respiratory droplets issue.
rather than by separate and individual virions. As the recyclability of disposable masks is
Therefore, based on the literature, the nanofiber going to become a big issue to the environment,
filters can capture the vast majority of respiratory it is necessary to make the disposable masks
virions. from biodegradable polymers urgently. It is also
Although the electrospun nanofibers have a good concept only if the filter within the mask
such good advantages, including better filtration is disposable, so the mask itself can be used
performance in the nanoscale compared with multiple times after disinfection. PLA is the
melt-blown fibers, optimizing their mechanical most popular material for FDM due to its easy
properties is still a big challenge. Therefore, the processability and commercial availability [14,15] . It
electrospun nanofibers must be combined with is an environmentally friendly polymer material
other supporting materials, for example, textile and can be entirely biodegradable under certain
fabric, plastic mesh, and metallic mesh to make conditions. Thus, the main goal of this study is
air filters . Direct coating, where the electrospun to prepare PLA electrospun nanofibers combined
[8]
nanofiber layer is deposited on the surface of the with 3D printed PLA part for disposable filters of
substrate, is the most common method to make such future masks. The layered filaments with a proper
combined structure. However, there are a few issues spacing support the nanofibers and simultaneously
with this process: (1) The conductive substrate can allow easy breath through. The transparent look
result in non-uniform deposition of nanofibers; (2) can help to avoid the threatening appearance of
as the nanofibers are very sensitive, it is difficult to the mask and can allow lipreading for people with
handle such flexible sheets without damaging the mutism or hearing impairment.

2 International Journal of Bioprinting (2020)–Volume 6, Issue 4