Open-Source System 3D Prints from Custom Powders
HOUSTON, Feb. 29, 2016 — An open-source laser sintering printer has been used to print intricate 3D objects from powdered plastics and biomaterials. The system costs a fraction of equivalent commercial systems and could give researchers a DIY technique for working with their own specialized materials.
"[elective laser sintering] technology has been around for more than 20 years, and it's one of the only technologies for 3D printing that has the ability to form objects with dramatic overhangs and bifurcations," said professor Jordan Miller of Rice University, who specializes in using 3D printing for tissue engineering and regenerative medicine. "SLS technology is perfect for creating some of the complex shapes we use in our work, like the vascular networks of the liver and other organs."
OpenSLS is an open-source, selective laser sintering platform that can print intricate 3D objects from powdered plastics and biomaterials. Courtesy of Jeff Fitlow/Rice University.
Called OpenSLS, the open-source device cost Rice bioengeering researchers less than $10,000 to build. Commercial SLS platforms typically start around $400,000 and can cost up to $1 million. However, commercial systems can’t be used with custom powdered materials, which can stand in the way of researchers who want to experiment with biomaterials for regenerative medicine and other biomedical applications.
OpenSLS works differently than most traditional extrusion-based 3D printers, which create objects by squeezing melted plastic through a needle as they trace out 2D patterns, the researchers said, and 3D objects are then built up from successive 2-D layers.
In contrast, the SLS laser shines down onto a flat bed of plastic powder. Wherever the laser touches powder, it melts or sinters the powder at the laser's focal point to form a small volume of solid material. By tracing the laser in 2D, the printer can fabricate a single layer of the final part. After each layer is finished, a new layer of powder is laid down, and the laser reactivates to trace the next layer.
The team showed that the machine could print a series of intricate objects from both nylon powder — a commonly used material for high-resolution 3D sintering — and from polycaprolactone, or PCL.
The tests using PCL, a biocompatible plastic that can be used in medical implants for humans, were particularly important, because it allowed demonstration of myriad shapes and surface textures. The increased surface area found on rough surfaces and in interconnected pore structures are preferred in some situations, while other biological applications call for smooth surfaces, said graduate student researcher Ian Kinstlinger.
Ian Kinstlinger developed a method for smoothing the surfaces (left) of newly printed scaffolds (right) using vaporized solvent. Courtesy of Jeff Fitlow/Rice University.
The team developed an efficient way to smooth the rough surfaces of PCL objects that came out of the printer by exposing the parts to solvent vapor for about 5 min, which provided a very smooth surface due to surface-tension effects. In tests using human bone marrow stromal cells — the type of adult stem cells that can differentiate to form bone, skin, blood vessels and other tissues — the researchers found that the vapor-smoothed PCL structures worked well as templates for engineered tissues that have some of the same properties as natural bone.
"The stem cells stuck to the surface of the templates, survived, differentiated down a bone lineage and deposited calcium across the entire scaffold," Kintslinger said.
The research was published in Plos One (doi: 10.1371/journal.pone.0147399).
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