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Article Cite This: J. Chem. Educ. XXXX, XXX, XXX-XXX

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A Simplified Method for the 3D Printing of Molecular Models for Chemical Education Oliver A. H. Jones*,† and Michelle J. S. Spencer*,‡ †

Australian Centre for Research on Separation Science (ACROSS), School of Science, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia ‡ School of Science, RMIT University, GPO Box 2476, Melbourne, Victoria 3001, Australia

ABSTRACT: Using tangible models to help students visualize chemical structures in three dimensions has been a mainstay of chemistry education for many years. Conventional chemistry modeling kits are, however, limited in the types and accuracy of the molecules, bonds and structures they can be used to build. The recent development of 3D printing technology has allowed a much wider variety of molecules to be created for teaching but is not simple to do. Creating the files needed to print molecular structures is often technically difficult and requires the use of multiple software programs, which are not always user-friendly. Not all educators or students have the resources or technical skill to create such files and so are put off trying to use 3D printing in the classroom. Here we demonstrate a simple method to easily generate the files needed for the 3D printing of almost any molecule using the National Institutes of Health Print Exchange server (or simple alternatives). The basic molecule structure may be created in-house or easily sourced online from databases such as UniProt or PubChem. The options for quickly and cheaply printing such structures in a range of materials using online and local stores, as well as in-house 3D printers, are explored and a simple protocol is described. The method brings 3D printing to a wider audience, thus helping to spread its use in chemical pedagogy, and may also be used in self-directed learning exercises by students themselves. KEYWORDS: Chemoinformatics, General Public, Hands-on Learning/Manipulatives, Molecular Modeling, Molecular Properties/Structure, Nanotechnology

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INTRODUCTION Students usually first encounter molecular structures as a two-dimensional (2D) representation on a page in a textbook or, increasingly, on a smartphone or tablet. Such pictures are a useful and convenient way of representing molecules but some information, such as atom size and shape, bond lengths and symmetry, is lost. It is therefore often difficult for students to visualize and understand the complex three-dimensional structure of molecules using only 2D representations. For this reason, models and kits that allow students to build a threedimensional version of molecules that can be easily handled and examined are established pedagogic tools in chemical education.1,2 Conventional chemistry modeling kits (such as Molymod ball and stick models) have been the backbone of chemistry classes for many years but they are limited in the types and accuracy of the molecules and structures that they can be used to build. Large inorganic complexes and biopolymers are very hard to represent with such systems for example, as are the complex shapes and periodic domains of nanostructures.1 A possible solution is the recent development of three-dimensional (3D) printing, an © XXXX American Chemical Society and Division of Chemical Education, Inc.

additive manufacturing process in which numerous thin layers of a material are laid down in succession under computer control to make a three-dimensional physical object from a digital model. 3D printing allows the creation of structures of almost any shape or geometry, simply and at low cost.2 Multiple materials can be used for 3D printing. The most common are plastics such as acrylonitrile butadiene styrene (ABS) and poly(lactic acid) (PLA). A range of other materials can be also be utilized including nylon and glass-filled polyamide, epoxy resins and photopolymers, gypsum and other ceramic materials, base metals such as bronze, steel and titanium and even precious metals such as gold.3 Using such materials, 3D models have been created of everything from complex mechanical parts and biomedical implants to simple plastic figures and models. The rise in the use of 3D printing has been driven by the fact that the cost of 3D printers themselves has fallen substantially in recent years while their functionality and Received: July 17, 2017 Revised: October 13, 2017

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reliability have increased. Today, 3D printers vary from large, specialized (and very expensive) machines printing metal parts for industry to simpler systems costing a few hundred dollars that are relatively easy to set up and use in the classroom. The uses of 3D printing within the field of chemistry are numerous, varied and growing. The technique has been used to make laboratory equipment and custom reaction vessels for chemical synthesis,4−6 create structures with inbuilt active chemistry,3 and develop many applications in separation science7,8 and microfluidics.9,10 In chemistry pedagogy 3D printing has been used to teach VSEPR theory,11 orbital theory,12,13 crystal symmetry and point groups14,15 and the operating principles of diffraction gratings16 among others. Creating the files needed to print molecular structures is often technically difficult. It usually requires the use of multiple software programs, many of which are not user-friendly and/or have a steep learning curve. Not all educators or students have the resources, time, or technical skill to create such files or learn how to do so and so are put off trying to use 3D printing in the classroom. Such reticence has, to date, hindered uptake of the technology despite its advantages. Here we demonstrate a way to easily generate files needed for 3D printing almost any molecule using the National Institutes of Health (NIH) 3D Print Exchange, an open, comprehensive, and interactive Web site for searching, browsing, downloading, and sharing 3D print files.17 The site automates the creation and optimization steps which can be used for any molecule, from small organic compounds and nanostructures to large biopolymers (as well as microscope and medical imaging data). The server can create a range of common 3D printing files, including the commonly used stereolithography (.stl) format from structures created in-house using software such as the Visual Molecular Dynamics (VMD) program or sourced online from databases, such as UniProt, PubChem and the Crystallography Open Database, or the Print Exchange server itself. Once created the printer files are stored on the server and can be downloaded and/or shared with others and then uploaded to a 3D printer local to the user or sent to an online commercial provider. While the method described here is not the first to illustrate how to convert a structure file into a 3D-printable format, it presents a number of advantages: • It is simple to do, requiring nothing but an Internet connectionan advantage over even the recent methods of Scalfani and Vaid15 and Rossi et al.18 • It provides files that are stable and compatible with all forms of 3D printers and online 3D printing services and which can be shared with others around the world. • It works with a range of original data formats including those of the tens of thousands of chemical structures stored in online data banks. The method greatly simplifies the process of 3D printing molecules and thus will help to spread the technique for both research and pedagogy in the chemical sciences. For comparison, this article also includes information on how and where to view, fix and print 3D print files and discusses the advantages and disadvantages of differing 3D printer materials and file formats. It therefore acts as a detailed guideline/synopsis for those looking to get started with 3D printing but who have little to no experience.

Article

METHODS

Print File Creation

Protein databank (.pdb) or structure-data file (.sdf) format files of various molecules’ chemical structures (see Table 1) were generated using the Visual Molecular Dynamics or Materials Studio Visualizer programs or downloaded from the UniProt19 or PubChem20 databases. There are other programs that can be used to generate structures of molecules or nanomaterials, including ChemDraw/ChemOffice, Avogadro, Gaussview, Discovery Studio Visualizer, Blender, Matlab, or Mathematica. Most of these are, however, not free or only available free to academic institutions. There are also online resources, such as the JMOL Crystal Symmetry Explorer web tool,21 for creating 3D printed chemical structures which are usually free but not as simple to use as the NIH Exchange. A variety of sizes and shapes were created in order to test the method fully; these were as follows: 1. Small molecule (i) fluorescent tag bound to fatty aciddesigned for a separate chromatography study (optimized structure obtained from a density functional theory simulation performed using GAUSSIAN)22 2. Protein (i) enzyme−horseradish peroxidase23 taken from the PDB database 3 2D nanomaterial (i) graphene sheet (built using VMD) (ii) silicene (built using Materials Studio) (iii) functionalized silicene (optimized structure obtained from a density functional theory simulation [performed using the Vienna ab initio Simulation Package (VASP)]24 Once created, the files were saved on a standard PC hard drive and shared between the authors using e-mail as well as the online tools Dropbox and Google Drive. A free account was then created on the publically available National Institutes of Health (NIH) 3D Print Exchange Web site,25 and the files were uploaded to the server via first clicking on the “create” tab on the Web site home page and then the “upload your files” option under either (1) “SMALL MOLECULES” (for models of chemical structures with fewer than about 100 atoms; the filetypes CIF, MOL, MOL2, PDB, and SDF can be used) or (2) “BIOMACROMOLECULES” (for proteins and other large biomolecular systems over 200 atoms in size; this option supports the upload of PDB, PDB1, CIF, ENT, GRO, MAE, MOL, or MOL2 file formats). If the user does not have a file to upload it is possible to use the “quick submit” function. This option allows the generation of a 3D-printable model by inputting a structure from PubChem or the Protein26 or Electron Microscopy27 databanks via the use of a database accession code (easily found on the respective Web sites) for the structure in question. Once the Print Exchange server had confirmed by e-mail that the files were ready, the Print Exchange Web site was accessed via user login and the relevant files were downloaded in multiple formats including STL and VRML (Virtual Reality Modeling Languagea standard file format for representing 3D interactive vector graphics) files. All files were viewed online prior to download and resized if necessary. After download, the models were stored in a standard USB thumb drive and also shared publically online for future use. N.B.: the interested B

DOI: 10.1021/acs.jchemed.7b00533 J. Chem. Educ. XXXX, XXX, XXX−XXX

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Table 1. Comparison of Some Images of Structures Printed, Their Material and Printer Source, and Dimensions

a

Availability of materials at universities and other printing sites may vary. bPrinted at Officeworks. cPrinted at Shapeways. dPrinted at RMIT University.

of other commercial 3D printing service providers such as i.materialize29 and Sculpteo30 that provide a similar service, but only the Shapeways site28 was used in this study. For options ii and iii the raw .stl files were taken on a USB drive and provided to the printer operator. A brief discussion over size and material was undertaken with the operator before the model was printed overnight and picked up the next day. The process described above is illustrated in Figure 1. The models printed by each method are shown in Table 1.

reader may search the Print Exchange site for the usernames “OliJ” or “Michelle” to see and download all the print files created by the authors during this research. Physical Model Creation

To enable a comparison of printing options, .stl files generated from the Print Exchange server were uploaded to one of three printing services: (i) the Shapeways online 3D printing service;28 (ii) a 3D printer (Projet 7000HD SLA model) at RMIT University; (iii) a local, store-based, 3D printing service in Melbourne Australia (Officeworks). For method i an account was created on the Shapeways Web site28 and various options for the printing and printing material(s) were selected (see Table 1). There are a number

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RESULTS AND DISCUSSION The authors had no previous experience in 3D printing. Despite this, several molecules, from graphene to horseradish C

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Figure 1. Flowchart of the process needed to create a molecular structure file ready for printing. The red boxes (top row) show the general printing process while the blue boxes illustrate the suboptions that are available at each stage. The black arrows indicate possible alternative routes that the user can follow to generate 3D prints of large or small molecules after the model upload stage. Asterisks (*) indicate software that is either not free or only free for academics.

Figure 2. Illustration of the variety of molecules and materials used in this study: (A) horseradish peroxidase C1A enzyme in UV-curable acrylate (upper) and blue plastic (lower); (B) fluorescent molecule printed in UV-curable acrylate (upper) and matte bronze steel (lower); (C) functionalized silicene in UV-curable acrylate; (D) nanosheets of graphene (left, polished gray steel) and silicene (right, polished gold steel).

chemistry projects. The students commented that by having 3D models that they could hold and rotate they were able to easily see the specific structure and features of the molecules or materials in question. For example, students could clearly see that while both graphene and silicene have the same honeycomb network arrangement of atoms, graphene is planar while silicene is buckled. With the functionalized silicene, students were able to easily see that the phenyl groups are not attached to every silicon atom but that some silicon atoms are terminated by hydrogen atoms. Since this structure has functional groups attached to both sides of the nanosheet, the arrangement of these chemical groups could more easily be determined

peroxidase, were successfully printed in a range of different materials, including resins and metal powder, with minimum effort (see Table 1 and Figure 2). The resulting method is quick and simple and could also be easily used in a practical classto allow students to print a molecule they had optimized in a computational chemistry assignment for example. The 3D printed models described here are currently being used in a number of undergraduate courses at RMIT University (Melbourne, Australia), including first year undergraduate Nanotechnology and second year undergraduate Biochemistry. The models are also used by undergraduate and postgraduate research students undertaking computational materials D

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Most .stl files can be viewed online.34 In the authors’ experience online .stl viewers tended to be simple, showing the print in only one color with limited viewing options and no repair features (although some sites will highlight where problems in the model are located). Again therefore, the NIH site was found to be superior for the novice user of a 3D printer. By automating the digital manipulation needed to create printable models that are often the steepest barrier to creating a 3D print, the NIH and similar sites greatly expand the potential user base of 3D printing technology, with significant pedagogical advantage. An additional benefit of the NIH Web site is that all models created are stored on the server for easy reuse and sharing. It is possible to keep a model private, if necessary, but it is difficult to remove a model from the database that you no longer want or that did not work out. Once a suitable .stl file is created, the next step is to decide on what material to use to print it. There are a number of materials available for 3D printing, each with their own pros and cons (indeed the choice of what to use can be overwhelming). Frequently used materials include plastic, metals, and ceramics with less typical options including paper and wax. A list of some of the more commonly available printing materials is given in Table 2, together with their availability, advantages, and disadvantages. Plastics are the most commonly used 3D printing material due to their low cost, abundance, and versatility. Such polymers include polyamide, flexible elastomer (nylon), photoreactive resins (UV-curable acrylate and acrylate-based materials), poly(lactic acid) (biodegradeable thermoplastic), acrylonitrile butadiene styrene, and poly(vinyl alcohol). Most of these materials are relatively cheap to print with prices ranging from ∼US $20−30 for small models to ∼US$100, depending on the size of the model and the exact material used. The final model quality can be quite variable. Cheaper materials usually correlate with lower printing quality (model resolution), so the user will need to weigh up their particular situation. In this study it was found that standard PLA produced low-quality models, particularly for small molecules. Metal is another 3D printing material which is becoming more popular due to advances in printer technology. Some pure metal models can be printed using either printed molds (composed of nonmetals), which are later removed, or industrial printers, which use high powered lasers to sinter or melt powdered material. The latter method is generally too expensive (and too dangerous) to use in an educational setting. Using pure metal in a standard 3D printer is impossible due to the extremely high temperatures needed for metal 3D printing. “Metal” models are often made from metal−PLA filaments that contain enough metal powder (which can be precious metals, stainless steel, or aluminum) to give the look and feel of a metallic object but enough plastic to be printed at the low temperatures (200−300 °C) achievable with benchtop 3D printers. Such models not only look like metal but are also more durable than plastic models and have higher resolution. Printing difficulty is high, however, as these models often require fine-tuning of nozzle temperature and flow rate, and the metal in the filaments increases wear and tear on the printer nozzle. Postprocessing (e.g. brushing, grinding, polishing, waxing or coating) may be required of metal 3D prints to achieve different finishes (commercial providers will do this as part of the service). In this study models were printed in gray steel, gold steel, and bronze steel with matte, raw, or polished finishes (see Table 2).

than by using a single, nonrotatable image. With the enzyme model the students were able to more easily identify the active site and the importance of the relationship between structure and function. We therefore believe that the use of 3D printed models in class is likely to be beneficial to the student’s tactile learning experience, although this was not formally evaluated. The advantage of the 3D Print Exchange site is the automation of the model creation step. This is important due to the complexity of performing model optimization by hand. A .pdb file is a text-based format. Each file contains a set of coordinates detailing the three-dimensional structures of a particular molecule including features such as atomic coordinates and connectivity. Digital printers can use a variety of types of geometry definition files including .obj (first created by Wavefront Technologies) which uses ASCII format (plain text) to describe vertex lines of coordinates and faces; it is often accompanied by a .mtl (Material Library) file, which references the materials and colors used. One of, if not the, most commonly used 3D printing formats, however, is the .stl file (originally termed stereolithography but now also known as “Standard Triangle Language” and “Standard Tessellation Language). Unlike .pdb files, .stl files describe only the surface geometry of a three-dimensional object (without any representation of color or texture) as a raw unstructured triangulated surface. When creating an .stl mesh from a .pdb (or similar) file, a number of errors can be introduced that can prevent the model from printing properly. These include holes in the mesh, inverted and/or unconnected sections, and intersecting faces. Previously these errors would need to be corrected by an experienced user with complex software such as Meshlab or Netfabb. These programs are all technically difficult to use and have a steep learning curve such that many are put off using them, or one person in a group becomes the “go to” person to help create models. Neither option is ideal. The 3D Print Exchange gets around this problem by automating the model correction step using an online (cloud-based) version of Netfabb, which automatically repairs models uploaded to the site. The resulting model is verified as printable before being returned and made available for download on the model page. The .stl file format is then converted by nearly all 3D printer build preparation “slicer” programs to generate the final build file for the printer. If a user does not wish to use the NIH Print Exchange, there are a number of other programs that will convert .pdb files to .stl format. These include UCSF Chimera, MeshLab, and PyMoL. These programs require significant user input and are much more difficult to use than the NIH Print Exchange. There are also alternative online tools to “fix” .stl files, such as Netfabb Online31 Trinckle32 and Make Printable.33 Users of such sites can upload a damaged file and download a fixed version. Such sites vary in their functionality and user interface. Most (but not all) of the non-NIH sites required a user account, and many charge fees if used more than a few times. In the authors’ experience none were as good at repairing files as the NIH Print Exchange site. The non-NIH sites were generally found to be of use only if the problems in the model were small and simple. Larger problems, such as significant holes in the mesh, were not easily fixed and in some cases extra mistakes were introduced, such as wrong holes being closed and/or important geometry being deleted, thus rendering the “repaired” .stl file of limited use. The authors therefore felt that overall the NIH site was the best tool for the repair of 3D print files of molecules. E

DOI: 10.1021/acs.jchemed.7b00533 J. Chem. Educ. XXXX, XXX, XXX−XXX

a

Flexible elastomer (nylon) UV-curable acrylic plastic Polylactic acid: biodegradeable thermoplastic Acrylonitrile butadiene styrene Poly(vinyl alcohol): water-soluble plastic used as support Nylon plastic filled with aluminum dust Gypsum (calcium sulfate hemihydrate) with binding material and colored ink Matte or gloss Wax Preprinted paper that is cut and glued into shape

Elastoplasticb High definition acrylateb,d

PLAb,c

ABSc

PVAb,c,d

F

Multicolor; matte and gloss Smooth finish Multicolor; environmentally friendly

Relatively cheap Multicolor; relatively cheap

Multiple colors, durable; smoother finish than PLA Recyclable; nontoxic

Flexible Ideal for detailed models with smooth surface finish Multiple colors; cheap

Cheaper than precious metal; multiple finishes in matte and polished Cheaper than precious metal but more expensive than steel Cheap Good choice for very fine details; frosted look Translucent to clear finish

Can print thin structures

Advantages

Availability of materials at universities and other printing sites may vary. bShapeways. cOfficeworks. dRMIT University.

Porcelainb Castable waxb Paperc

Acrylic-based photopolymer

Acrylic plasticb

Ceramic Organic

Fine polyamide UV-curable acrylic plastic

Strong and flexible plasticb Frosted detail plasticb

Metallic plasticb Full color sandstoneb,c

Raw aluminum

Gold (white, yellow, rose); sterling silver; plated metal (gold rhodium); brass; bronze; platinum Steel; brass; bronze

Description

Aluminumb

Metal alloyb

Precious metal

b

Typea

Plastic/metal Powder

Plastic

Metal

Material

Table 2. Selection of Materials Available For 3D Printed Models and Their Properties

More brittle than other plastics Intricate/thin features not strong; resolution of features can be low; water will run colors Fragile Fragile Resolution of features can be low

Deterioration in air due to moisture; expensive

Fine features can be brittle; cannot do models with cavities (as cannot remove waxy support); slightly more expensive than other plastics Print lines/layers may be visible Removal of supports may leave rough surfaces; slightly more expensive than other plastics Needs thicker walls then ABS; not as durable and flexible as ABS; print lines/layers may be visible; Removal of supports may leave rough surfaces Deterioration through sunlight

Print lines/layers may be visible; resolution of features can be low Fine features can be brittle

Removal of printing support can cause marks on final model

Removal of printing support can cause marks on final model

Expensive

Disadvantages

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(see Figure 2). It is therefore recommended that new users start with these materials and consider other options, such as ceramics and sandstone (if needed) as they become more experienced. Students may also enjoy exploring the different printing options available and discussing the chemical composition and properties of the differing materials used. Another option to bring chemistry to the process is the use of what is known as the acetone vapor technique, which is used to give a high gloss finish and to smooth-out rough surfaces in low resolution models made of ABS (N.B. this method does not work with PLS). This method involves simmering a small quantity of acetone in a deep beaker or tin on a hot plate and suspending the model on a wooden platform or metal foil sling within the vapor created by the heat. This method has the potential to dissolve models if they are left in for too long, so caution and appropriate health and safety precautions for acetone use are advised. The advantage of using 3D printed models is that they can be made to scale and have any combination and numbers of atoms required. Conventional modeling kits are often limited in the number of heteroatoms (such as Si and N) that they include. The bond lengths are also fixed which means that models made with them can have unrealistic dimensions and geometries. This can make the use of such models limited for chemical education purposes. The use of 3D printing in the classroom not only allows students a new way to visualize molecules but can also be used to facilitate discussion on the chemistry of the printing materials themselves. A potential disadvantage of printing molecules for use in the classroom is that the ball and stick models allow the user to experience different combinations of atoms; thus, different molecular geometries can be displayed with a given number of atoms and bonds. By 3D printing a molecule in one go the user cannot assemble the molecule from parts, which is itself a pedagogic activity. This issue can be overcome, however, by 3D printing atoms and bonds in a molecule individually and then assembling the pieces in class, although such an activity would require some modification of chemical structures in the print file. The NIH 3D Print Exchange does not offer the ability to modify 3D print files but the previously mentioned JMOL 3D web tool does. The disadvantage is, however, that unlike the NIH Print Exchange the JMOL tool does not allow users to share the structures in a repository. The authors also found the JMOL tool was not as simple to use as the NIH exchange and since the aim of this article was to create a simple method that worked quickly and easily for all potential users, it is felt that the NIH Print Exchange is the better option at present. Those interested in exploring the JMOL tool further are encouraged to read the excellent work by Scalfani et al. on the subject.21

The cost for printing in metal again varies by the size of the model, ranging from around US$20−30 for steel and bronze to almost prohibitively high for even modestly sized models printed in precious metals. For example, to print the graphene model in this study (approximate dimensions of 5 cm × 7 cm × 0.5 cm) in platinum would cost more than US$6,700.00 at the time of writing (July 2017). It is also possible to 3D print using ceramics (either clays or porcelain). As with metals, such models generally require industrial printing technology and postprocessing of the model. Ceramic prints have a much smoother finish than plastic or metal as well as enabling many colorful printing options at a medium cost. They are, however, usually very fragile and would not be a good choice for a print that is handled regularly (e.g. in classrooms). Other (rarer) printing materials include paper and sandstone. The latter is generally sprayed as a powder in conjunction with a binding agent and incorporating colored inks. Both allow for printing models that have multiple colors, but they are often not inherently water resistant (unless coated) so water may cause the colors to run. They also do not allow for high levels of detail in the model, and costs can be high. Sandstone models are, however, a good choice for presentations as they allow for full color, photorealistic models and sculptures. Note that .stl files usually only allow printing in one color. However, two or more .stl files (each of a different color and representing different parts of a structure) can be combined for a more complex model. Since this option is technically difficult, it is easier to download files in the VRML format as this allows surface color and other features to be specified for a 3D polygon as well as vertices and edges. VRML files are commonly called “worlds” and so have the extension .wrl (for example, chemistry.wrl) rather than .vrml. Another common 3D printing file that allow the use of color is the .obj format. Despite the many advancements in recent years, one of the main issues that prevents the wider adoption of 3D printers is the lack of easy color printing. While there are many industrial printers that can print multicolor objects, most 3D printers work with single color, primarily because of the difficulties associated with getting multicolor output from a filament or resin. Printing in multicolor requires either multiple print heads, which require more parts, wiring, and software (the extra weight also makes the system harder to calibrate and slower to print and reduces the print size) or a tool to manage different filaments in the same nozzle (such as the Mosaic PALETTE+ system) Such systems are expensive but growing in usability and popularity. A simpler option is postprocessing, e.g., to apply paint to a single color print after it has been created. Whichever material is used, it is worth bearing in mind that more complex models (such as proteins or supramolecular models) may require supports to be added to the model during the printing process which must later be removed (N.B.: any material, such as sandstone, where prints are created in a powder bed do not require supports). Depending on the material used and the shape of the model being printed, these can sometimes be removed easily. With complex models, however, removal of supports can leave marks on the model, and if the model is very intricate, it can be difficult to get access to the support material to remove it. Both scenarios can lead to a lower quality final product. In the current study it was found that for chemistry teaching the metal and plastic (with the exception of PLA) options provided good quality, robust models of all the molecules and structures tested at a reasonable cost

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CONCLUSIONS A simple method to source and convert chemical structures to 3D-printable models quickly and simply has been described and alternatives discussed. This procedure is free to use and requires only an Internet connection and access to a 3D printer. Programming knowledge and/or familiarity with complex software is not necessary. The protocol is therefore highly beneficial and well suited to use in a school or university environment to allow students to create and use models that allow them to visualize chemical structures and/or are a discussion point for materials chemistry studies. It can also be used to generate discussion of the chemical properties of the printing materials themselves. In a research context 3D printing and G

DOI: 10.1021/acs.jchemed.7b00533 J. Chem. Educ. XXXX, XXX, XXX−XXX

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accurate physical modeling can give researchers a third angle to approach their problems, adding physical modeling to experiment and computer simulation. Simplifying access to 3D printing therefore has great potential benefits to the chemical sciences as well as chemical pedagogy and self-directed learning exercises.

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AUTHOR INFORMATION

Corresponding Authors

*(O.A.H.J.) E-mail: [email protected]. *(M.J.S.S.) E-mail: [email protected]. ORCID

Oliver A. H. Jones: 0000-0002-4541-662X Michelle J. S. Spencer: 0000-0003-4646-1550 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Paul Porter of the RMIT University Advanced Manufacturing Precinct for assisting with printing some of the models described in this work.

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REFERENCES

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DOI: 10.1021/acs.jchemed.7b00533 J. Chem. Educ. XXXX, XXX, XXX−XXX

Journal of Chemical Education

Article

(30) Sculpteo Online 3D Printing Service, https://www.sculpteo.com/ en/ (Accessed October 2017). (31) Netfabb Online, https://service.netfabb.com/ (Accessed October 2017). (32) Trinckle, https://www.trinckle.com/ (Accessed October 2017). (33) Make Printable, https://makeprintable.com/ (Accessed October 2017). (34) STLfile Online Viewer, https://www.viewstl.com/ (Accessed October 2017).

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DOI: 10.1021/acs.jchemed.7b00533 J. Chem. Educ. XXXX, XXX, XXX−XXX