3D Printing in Chemistry

Fused Deposition Modeling (FDM) is the cheapest and the most simple method of three-dimensional (3D) printing. The method involves the part or model being produced by extruding small flattened strings (around 2 mm) of molten material to form layers, as the material hardens immediately after extrusion from the nozzle. A plastic filament or metal wire is unwound from a coil and supplies material to an extrusion nozzle, which can turn the flow on and off. There is also a worm-drive that pushes the filament into the nozzle at a controlled rate.

The process of three-dimensional printing of chemical equipment using FDM printer.

The nozzle is heated to melt the material. The thermoplastics are heated above their glass transition temperature and then deposited by an extrusion head. The nozzle follows a tool-path controlled by Computer Aided Manufacturing (CAM) software package, and the part is built from the bottom up, one layer at a time. The nozzle diameter and thickness define the resolution of FDM printer. The design of the 3D printer is relatively simple. As many companies manufacture them, the cost is quite low. Another significant advantage is the low cost of the materials used in FDM, such as acrylonitrile butadiene styrene (ABS), a biodegradable polylactide (PLA), polyethylene terephthalate (PET), polypropylene (PP), nylon, polycarbonate, and others.

The method of fusing a polymeric strand has average spatial resolution (typically 0.1 - 0.2 mm), which allows the manufacture of parts of different shapes and levels of complexity (Fig. 1). Huge possibilities of 3D printing make it promising for education and science, especially for the production of unique laboratory equipment and visual aids (Fig. 2), layouts, and models (including those with moving parts).

Fig. 1. The spiral channel bracket made using two different polymers from two extruders operating simultaneously. The picture demonstrates the final product and three-dimensional model.

Fig. 2. Round-shaped molecule model, made by FDM from PLA. High quality model is made from assembled parts.

High chemical stability of certain polymers (such as polypropylene, nylon, polyethylene terephthalate) in combination with FDM method corresponds well to the needs of chemical laboratory. However, the real breakthrough potential of 3D printing is disclosed not in the manufacture of standard laboratory equipment, but in construction of special products for unique laboratory needs, such as chemical reactors, mixers, and other elements of chemical apparatus.

Layered fusing technology has developed enough to reproduce even the subtle details of small chemical equipment. For example, Figure 3 demonstrates an image of a mixer with three inputs and one output pipe. The diameter of the inner channel of the mixer is only 2 mm. Conical notches are clearly visible on the inlet, and the height of the incisions is 0.5 mm. Miniature helical rib is designed to increase the mixing efficiency. This is not yet engraving the name on a grain of rice, but we should also consider that the manufacture of the mixer took less than 30 minutes. Try to make it using conventional tools!

Fig. 3. Mixer inside the 3D printer.

Fig. 4. PET chemical microreactor with a sophisticated labyrinth inside. The image shows details of the reactor design and the full assembly.

The possibility to manufacture products with complex internal structure is one of the main advantages of 3D printing. This feature is well illustrated in Figure 4, which shows the chemical reactor the size of a matchbox. Likewise "a real" chemical reactor, the "baby reactor" has a shell, and the cover is connected to the shell by bolts and gasket for sealing the workspace. Take a look under the hood to see the complexity of the inner world: labyrinth channel is built to force the reaction mixture to take a difficult path, so that the reaction time is optimal for producing the desired products. The walls at the bottom of the labyrinth channel are thin, in order to keep the catalyst from the rapid washout. The reaction products leave the reactor through the lower inlet.

Fig. 5. Microreactor can consist of any number of elements, and each one is produced by 3D printing.

Fig. 6. Mixer and micro reactor made of PET.

Fig. 7. Fused deposition modeled "plant": mixer and microreactor combined.

3D printing can significantly speed up the experimental chemical research, as it makes possible to manufacture even complex multi-component chemical equipment directly in the laboratory without a significant delay. This applies both to the fundamental chemical research, as well as to research and engineering projects. As for chemical engineering, 3D printing provides a truly unique opportunity to produce a series of reactors or other equipment with a variety of design parameters to find the optimal solution. The cost of production of even entire series of products using FDM is rather samll in comparison to the cost of commercial laboratory equipment. We believe that this innovation can be a valuable tool in the creation of research equipment in chemical sciences.

An example of using 3D printing in the design of photochemical reactor:

"Visible Light Mediated Metal-free Thiol–yne Click Reaction", Chem. Sci., 2016, 7, 6740-6745, DOI: 10.1039/C6SC02132H. On-line link: http://dx.doi.org/10.1039/C6SC02132H