## 4 Materials for SLA
### Graphene Composites  
#### 4.2.1 Overview of Graphene  
Graphene is a nanomaterial consisting of ultra-thin sheets of sp\({}^{2}\) carbon atoms arranged in a honeycomb lattice structure, well known for its electronic, magneto-electronic and optoelectronic properties [79]. It was isolated from bulk graphite using mechanical exfoliation (via the \"Scotch-tape\" technique) [80], which is not a method suitable for mass  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type of** & **Functionality** & **Other Ingredients** & **Printing Conditions** & **Properties of the Printed Structure** & **Ref. ** \\ \hline \multirow{4}{*}{Gelatin} & \multirow{4}{*}{Metheacrylamide} & 0.5\% Irgacure 2959; & \multirow{4}{*}{Gentric atmosphere, UV} & Homogeneous distribution of cells in the 3D-printed scaffold; & [78] \\  & & & neural stem cells & light & well-defined architecture of the bioprinted hydrogels & \\  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline \multirow{4}{*}{Gelatin} & \multirow{4}{*}{Metheacrylamide} & 0.5\% Irgacure 2959; & \multirow{4}{*}{Gentric atmosphere, UV} & 200 \(\mu\)m diameter laser & \multirow{4}{*}{Gentric atmosphere, UV} & \multirow{4}{*}{Gentric atmosphere, UV} \\  & & PEGDA (20\%); graphene oxide (0, 0.05, 0.1, 0.25, & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline \multirow{4}{*}{Soybean oil} & \multirow{4}{*}{Acrylate} & \multirow{4}{*}{Irgacure 819} & \multirow{4}{*}{The layer thickness and width} & \multirow{4}{*}{decreased dramatically with the increase in print speed, but slightly increased with increasing laser frequency. The compression modulus is not affected by differences in laser frequency. High attachment and proliferation of nMSCs} \\ \hline \multirow{4}{*}{Soybean oil} & \multirow{4}{*}{Acrylate} & \multirow{4}{*}{Irgacure 819} & \multirow{4}{*}{Halogen lamp (\(\lambda=390-450\) nm); & The functionality and the number of functional groups per oligomer tunes the stiffness and toughness of 3D products. Specifically, ESOMA\({}_{3}\) provides more stiffness and tensile strength than ESOA\({}_{3}\) and ESOMA\({}_{2}\) photoreins. & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline \multirow{4}{*}{Soybean oil} & \multirow{4}{*}{Acrylate, di/trinfunctional methacrylate} & \multirow{4}{*}{Isobornyl methacrylate, BAPO (1\% \(w/w\))} & \multirow{4}{*}{The resins were printed using Formlabs Form 2 printer under default settings} & \multirow{4}{*}{The resin is generated using Formlabs Form 2 printer under default settings} & \multirow{4}{*}{The resin is generated using Formlab Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabs Formlabslab Formlabs Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlabslab Formlablabslab Formlabslab Formlabslab Formlablabslab Formlab Formlabslab Formlablabslab Formlablab Formlabslab Formlablabslab Form  
scale production. The method developed by [PERSON] in the late 1950s consists of the treatment of commercial graphite powder with oxidizing agents and strong acids [81]. The resulted material is actually graphene oxide, which can be further reduced through thermal [82] or chemical [83] methods, creating the so-called reduced graphene-oxide (rGO). Probably the most effective reductant is hydrazine [84], but its toxicity to humans and the environment boosted the scientists to find greener alternatives [85]. Other graphene production methods refer to ion implantation [86; 87], liquid-phase exfoliation [88; 89], epitaxial growth upon a silicon carbide substrate [90; 91] and, the most significant chemical vapor deposition (CVD) [92; 93; 94].