3-D PRINTING AS TOOL FOR TEACHING CRYSTALLOGRAPHY

One of many challenges in teaching geology is fostering student understanding of the submicroscopic symmetric structures that comprise crystalline solids and the physiochemical rules that govern the development of these structures. We describe a project that uses 3-D printing of ball-and-stick molecular models in an attempt to teach crystallography and crystal chemistry in a semester-long, upper-level Earth Materials course (combined mineralogy and petrology). The project required a larger proportion of class time than would normally be allotted to crystallography in an Earth Materials course and, given that this was the first academic 3-D printing project at our institution, there was considerable time investment from the instructor and support staff; however, the 3-D printing aspect of the project facilitated student engagement and excitement and anecdotal evidence from comprehensive examinations administered 1.5 years later for 4 of the students in the class suggests high levels of retention.

This project workflow starts in CINEMA 4D, a 3-D modelling and animation software platform that allows users to position scaled polyhedral elements (in this case, spheres for ions, cylinders for bonds, and platonic objects for coordination polyhedra) to x,y,z coordinates based on a combination of Pauling’s Rules, XRD-derived bond lengths, and simple trigonometry. Other software applications (like CrystalMaker) can use inputs from crystallographic databases to produce similar printed results; however, while this would reduce the students’ time required considerably, it would also drastically limit the educational utility of the project. The ProJet 260C (3D Systems, Inc.) printer used in this project uses a 64 color palette and high spatial resolution (0.004”) which allows students to design intricate structures that can be creatively colored. Practical considerations centered on developing printable models that were small enough to limit printing costs but large enough to be robust under delicate handling. Additional applications of 3-D printing in geoscience education discussed will include similar software-hardware workflows for visualizing/teaching concepts in hydrology and geomorphology using digital elevation models (arcMap) and inputs from digital photogrammetry (PhotoScan).