# Additive Manufacturing and Chemical Engineering: Looking for Synergies from a Bibliometric Study
## 4 Review of Research Focused on Additive Manufacturing and Chemical Engineering
### Additive Manufacturing and Chemical Engineering: Future Needs
#### 4.2.6 Additive Manufacturing and Separation Membranes  
The revolutionary approach of additive manufacturing to achieve micro- and nanoscale resolutions has sparked researchers' interest in its application to separation membrane synthesis, with specific applications ranging from wastewater treatment to water-oil separation and purification of gases [165], representing a significant step towards improved separation processes. The most recent advances in additive manufacturing to achieve greater scalability, material processability, shorter processing times, and higher resolution have promoted the exploration of its potential to produce membranes with specific designs using typical membrane materials. Many applications involve processes based on material jetting, specifically inkjet printing and electrospray printing (also known as electrospinning), due to their ability to produce thin films even when working with mixed matrix membranes. Most powder bed fusion, material extrusion, or vat polymerization processes are not able to achieve the resolutions required for the production of effective membranes [165]. Inkjet printing utilizes a computer printer that ejects ink droplets onto substrates to form a desired pattern, while electrospray printing employs an electrostatic spraying process to deposit material onto a surface in a precise and controlled manner. Electrospinning, in particular, has emerged as a highly valuable technique for the production of thin-film composite membranes, offering precise control over thickness and the ability to deposit polymers for subsequent film formation [166]. This technology has proven highly adaptable to a wide range of separation needs, crucial in a context where membrane customization is essential due to the diversity of fluids to be treated and the different characteristics of the chemicals to be separated. Examples of thin-film composite membranes produced using inkjet printing and electrospinning are presented in Figure 19[165]. In Figure 19a, the inkjet printing process is de  
Figure 18: Examples of microreactors produced by additive manufacturing: (**A**) a silicone microreactor loaded with Au/TiO\({}_{2}\) photocatalyst (1) and a detailed optical microscopy image of the catalytic layer deposited over a microchannel (2) (Reprinted with permission from Ref [162]. 2016, Elsevier); (**B**) an electrochemical microreactor with structured platinum-coated electrodes and channels (Reprinted with permission from Ref [163]. 2020, John Wiley and Sons). picted, where patterns of fluorinated amine surface are printed on an m-phenylenediamine-impregnated support, followed by immersion in a trimesoyl chloride solution for interfacial polymerization [167]. The complete set of different patterns generated can be observed. Figure 19b shows an aqueous solution of m-phenylenediamine printed via inkjet printing on the support, followed by immersion in the trimesoyl chloride bath for polymerization [168]. Figure 19c displays a selectively controllable polyamide layer printed via electrospinningning [169], while Figure 19d exhibits mixed matrix membranes of carbon nanotubes functionalized with polyamide and carboxylic functional groups, also obtained using electrospinningning [170]. Finally, Figure 19e illustrates a selective nanofiltration polyamide layer printed via electrospinningning on a Span 80 intermediate layer [171]. The need to address wastewater treatment, especially industrial oils effluents, has driven the search for efficient and environmentally friendly manufacturing methods to produce highly selective and permeable membranes for this specific purpose. Additive manufacturing technologies have proven to be a promising solution, allowing flexible, solvent-free, three-dimensional design with enhanced energy efficiency [172]. Despite the potential benefits, it is important to note that membranes produced using additive manufacturing may face challenges such as higher susceptibility to fouling, particularly in oil-water separation applications.