Page 203 - IJB-10-6

International Journal of Bioprinting Effect of G/GO on photocurable resin structure

and reducing waste. Among various AM techniques, uniform distribution of these nanomaterials within UV-
vat polymerization technologies, based on the use of curable resins. 7,12,13 It is interesting to highlight that the
photocurable resins such as stereolithography (SLA), have chemical functionalization of GO is easier than G thanks
gained significant attention due to their ability to produce to its oxygen-containing functional groups. 14
high-resolution parts with excellent surface finish. 1 Nevertheless, integrating G and GO into photocurable
One of the most promising examples of the use of resins for three-dimensional (3D) printing poses unique
photocurable resins is in the biomedical field, where challenges, like the low content of printable G and GO,
their application has gained significant popularity in high cost, and uncured photosensitive resins. Contrary to
recent years. This growth is driven by the development expectations, several studies have found that the addition
2,3
and commercialization of resins certified for biomedical of these nanomaterials does not consistently enhance
applications. As a result, there has been a proliferation the mechanical properties of these resins, even with
of applications, including the creation of patient-specific adequate dispersion. 13,15,16 The most significant challenges
models and functional parts, implantable devices, include insufficient curing of the resin due to nanoparticle
particularly in dentistry, and short-term implantable absorption of UV light, the induction of anisotropy
devices. The ability to produce highly accurate and in composites caused by the inherent alignment of G
customized medical components has made vat sheets, increased internal stresses from resin shrinkage,
polymerization techniques indispensable in modern and compromised adhesion between layers. However,
medical practice. While the biomedical field represents the precise nature and extent of these effects remain
a key area of application, photocurable resins are also incompletely understood, necessitating further research to
being explored for various other innovative uses across comprehensively discern their mechanisms and conditions,
different industries. 4 thereby facilitating the optimization of the development of
these materials.
The incorporation of graphene-based nanomaterials
(GBN), such as graphene (G) and graphene oxide (GO), into In the context of layer adhesion and internal stresses,
ultraviolet (UV)-curable resins has opened up new avenues it has been observed that the presence of GBN can either
for enhancing the mechanical and functional properties enhance or hinder these properties. This variation largely
of materials fabricated through vat polymerization depends on their interaction with the polymer matrix,
technologies. The unique two-dimensional structure of G, distribution, and dispersibility. On one hand, GBNs, due
5
characterized by a single layer of carbon atoms arranged to their rigid structure, could potentially mitigate these
in a hexagonal lattice, imparts exceptional mechanical stresses by providing a reinforcing network. Conversely,
strength, electrical conductivity, and thermal stability. non-uniform dispersion or aggregation of GBNs can
6
GO, a derivative of G, offers additional functional groups intensify internal stresses, counteracting their potential
that can facilitate dispersibility and bonding within the reinforcing benefits.
polymer matrix. In relation to the challenge of achieving an adequate

One of the most promising aspects of GBN-reinforced degree of polymerization, a significant issue arises with
resins is the potential improvement in mechanical properties. the use of GBN in photocurable 3D printing materials.
Studies have shown that even a minor incorporation of G G strongly absorbs light, especially at the critical
or GO can yield substantial increases in tensile strength, photopolymerization wavelength of around 405 nm,
Young’s modulus, and fracture toughness. Beyond impeding sufficient light penetration to the polymer
7–9
17
mechanical enhancements, GBNs have also demonstrated resin. This often results in under-polymerization of
the capacity to improve thermal and electrical conductivity the polymer matrix, leading to a notable decrease in
stiffness and strength when compared to the base polymer
in photocurable resins. Consequently, this advancement without G. Several researchers have concentrated their
17
has promoted the development of UV-curable resins efforts on enhancing the mechanical properties of SLA
with multifunctional properties, suitable for applications 3D-printed samples by employing various post-treatment
that range from structural designs to electronics and
thermal management. 5,10 methods aimed at ensuring complete resin curing. These
investigations have demonstrated that post-treatment
It has been demonstrated that achieving proper highly affects the properties of the final material. 18,19 Despite
dispersion of GBN within the polymeric matrix is crucial these efforts, it appears that these approaches do not fully
for unlocking the full potential of these nanomaterials in resolve the issue, indicating that the problem of achieving
enhancing composite properties. Various techniques, optimal mechanical properties in SLA-G-printed materials
11
including ultrasonication, functionalization of GBNs, and extends beyond merely ensuring complete curing of
the use of surfactants, have been employed to ensure the the resins.

Volume 10 Issue 6 (2024) 195 doi: 10.36922/ijb.4075