An overview of sterolithography (STL).

Figure 1 Arthur J. Olson, Ph.D., Professor / Director, Molecular Graphics Laboratory, Molecular Biology Department, The Scripps Research Institute, La Jolla, California, shown seated in front of a Z Corporation stereolithography printer, and samples of 3-D molecular models that were created in his laboratory. Figure 2 The wood-like model (left) depicts the molecular surface of the beta-lactamase enzyme. This enzyme can confer drug resistance to some bacteria. This model was made on the Helisys rapid prototype machine – built up by laminating layers of paper, which have been cut with a laser. The amber-plastic model (right) depicts an assembly of pilin protein subunits. These subunits assemble to form long projections that stick out of bacterial cells, that can attach to other cells (and infect). This model was made on a 3D Systems Stereolithograpy rapid prototype machine – built up by photo polymerizing a resin with a laser, layer-by-layer. Stereolithography (STL) is a relatively new technology that enables fabrication of 3-D prototype models. More than two dozen years ago the technology evolved from the need in the manufacturing industry to pre-visualize objects before they were mass produced. Prior to STL, prototype models could only be made through very time consuming methods which included manually cutting plastic, carving wood, and shaping clay. Later, computers with computer-aided-design (CAD) and computeraided-modeling (CAM) software were capable of creating 3-D images. Finally, the CAD/CAM technologies were harnessed to drive devices called “printers” that made 3-D models from a variety of materials. This technique is generally referred to as rapid prototyping (RP). The ability to create a tangible 3-D object had wide appeal for a variety of applications including molecular biologists studying complex individual molecules and intricately detailed molecular structures (Figure 1). The initial printers, resembling offi ce copy machines, made models from paper and various plastic materials. Models made of paper were constructed from printers that laid down hundreds of very thin layers of fused paper and glue. The plastic models were virtually carved by lasers from blocks of plastic or from layers of molten polymers. Although all of these various RP techniques created solid 3-D models, the paper and plastic type materials were somewhat limited in delineating fi ne details and could only be produced in one color (Figure 2).