# Additive Manufacturing and Chemical Engineering: Looking for Synergies from a Bibliometric Study
## 3 Results and Discussion
### Bibliometric Network Analysis
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Cluster** & **Number of Documents** & **h-index** & **Cites** & **Centrality** & **Density** \\ \hline
**Subperiod 1 (2002-2017)** & & & & & \\ Chemistry & 118 & 54 & 11,910 & 386.42 & 103.97 \\ Cell Culture & 76 & 47 & 7657 & 266.77 & 45.20 \\
3D Printers & 369 & 83 & 27,622 & 148.69 & 38.17 \\ Bone Prosthesis & 52 & 36 & 5430 & 183.87 & 47.02 \\ Scanning Electron Microscopy & 55 & 35 & 5646 & 143.35 & 13.46 \\ Fused Deposition Modeling & 57 & 13 & 798 & 38.42 & 22.15 \\ Melting & 37 & 28 & 3323 & 26.58 & 12.30 \\
**Subperiod 2 (2018-2019)** & & & & & \\ Tissue Engineering & 56 & 33 & 2866 & 122.11 & 81.57 \\
3D Printers & 466 & 62 & 14,441 & 124.65 & 31.47 \\ Powder & 44 & 24 & 2208 & 60.33 & 18.93 \\ Bone & 33 & 21 & 1723 & 98.50 & 16.78 \\ Microstructure & 53 & 27 & 2145 & 61.96 & 13.28 \\ Fused Deposition Modeling & 78 & 20 & 1341 & 33.36 & 14.78 \\ Heat Transfer & 28 & 16 & 831 & 13.29 & 6.84 \\
**Subperiod 3 (2020)** & & & & & \\ Chemistry & 53 & 24 & 1827 & 84.35 & 64.35 \\
3D Printers & 377 & 45 & 8575 & 83.04 & 21.75 \\ Selective Laser Melting & 60 & 20 & 1291 & 25.26 & 32.22 \\ Mechanical Properties & 40 & 15 & 957 & 35.57 & 3.18 \\
**Subperiod 4 (2021)** & & & & & \\ Tissue Scaffold & 65 & 20 & 1265 & 95.23 & 59.05 \\ Particle Size & 92 & 20 & 1368 & 61.73 & 26.67 \\ Additives & 331 & 30 & 4265 & 79.65 & 14.13 \\ Biocompatibility & 44 & 16 & 649 & 86.16 & 12.95 \\ Fused Deposition Modeling & 36 & 12 & 383 & 10.04 & 4.07 \\
**Subperiod 5 (2022)** & & & & & \\ Tissue Scaffold & 55 & 10 & 380 & 86.87 & 61.56 \\ Powder Bed & 417 & 17 & 1806 & 88.20 & 51.91 \\ Biomechanics & 55 & 10 & 358 & 78.09 & 14.33 \\ Austenitic Stainless Steel & 44 & 8 & 188 & 40.80 & 33.66 \\
3D Printing & 140 & 13 & 743 & 61.43 & 8.05 \\ Deposition & 53 & 7 & 169 & 25.42 & 5.91 \\ Selective Laser Melting & 34 & 6 & 115 & 27.51 & 7.95 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Number of documents, h-indexes, cites, centrality, and density values of the different clusters identified in the bibliometric network analysis. the fourth subperiod with the cluster \"_Biocompatibility_\" (Figure S22). Several connections were observed when the cluster structure was analyzed, mostly of similar magnitude, with a notable emphasis on the connection between the keywords _Biocompatible Materials_ and _Polymers_. In the last subperiod, the theme was renamed to \"_Biomechanics_\" (Figure S26). During this subperiod, the strongest connections were modified, highlighting two main ones: the one between _Polymers_ and _Unclassified Drug_, and the one linking _Cell Culture_ and _Cell Engineering_. The topics derived from this second couple could be directly related to the first cluster family and the keyword category Biofabrication. The biocompatibility and biomechanics of materials produced by additive manufacturing have gained relevance and the interest in the manipulation and cultivation of cells in controlled environments to investigate the interactions among these materials and additional drugs in the framework of cellular processes and tissue engineering is worth mentioning [63; 64; 65; 66; 67]. The increasing importance of these research topics was confirmed by the evolution from a basic and transversal theme represented by the cluster in the fourth subperiod (Figure 8) to a motor theme in the last subperiod (Figure 9). After a review of the clusters representing motor themes not previously mentioned, the presence of \"_Cell Culture_\" and \"_Physiology_\" in the first subperiod and \"_Cell Proliferation_\" in the second subperiod must be highlighted. The cluster \"_Cell Culture_\" (Figure S2) included keywords such as _Cells_, _Cell Engineering_, _Cell Adhesion_, _Cell Proliferation_, and _Cell Survival_, which clearly invoked once again the topics related to the keyword category Biofabrication, where the interactions between cells and materials produced by additive manufacturing are critical.