Bioengineering researchers at Rice University have modified a commercialgrade CO2 laser cutter to create OpenSLS, an open-source, selective laser sintering (SLS) platform that, they say, can print intricate 3D objects from powdered plastics and biomaterials. The low-cost system costs about 40 times less than commercial counterparts and can allow researchers to work with their own specialized powdered materials.
“SLS 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 Jordan Miller, an Assistant Professor of Bioengineering 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.”
Miller said that commercial SLS machines generally don’t allow users to fabricate objects with their own powdered materials, which is something that’s particularly important for researchers experimenting with biomaterials.
“Designing our own laser-sintering machine means there’s no company-mandated limit to the types of biomaterials we can experiment with for regenerative medicine research,” said Ian Kinstlinger, a graduate student in Miller’s group who designed several of the hardware and software modifications for OpenSLS.
The Rice engineers demonstrated that their machine could print a series of intricate objects from both nylon powder, which is commonly used for high-resolution 3D sintering, as well as from polycaprolactone (PCL), a nontoxic polymer commonly used to make templates for studies on engineered bone. They also explained that they open-sourced all the hardware designs and software modifications and shared them via Github.
How It Works
The Rice OpenSLS platform works differently than most traditional extrusion-based 3D printers, which create objects by squeezing melted plastic through a needle as they trace out twodimensional patterns. Three-dimensional objects are then built up from successive 2D 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 two dimensions, 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.
“Because the sintered object is fully supported in 3D by powder, the technique gives us access to incredibly complex architectures that other 3D printing techniques simply cannot produce,” Miller stated. “The cutter’s laser is already in the correct wavelength range—around 10 micrometers—and the machines come with hardware to control laser power and the x-axis and yaxis with high precision.”
How It Evolved
In Summer 2013, Miller hosted a fourweek crash course in hardware prototyping, the Advanced Manufacturing Research Institute (AMRI). One AMRI participant, Andreas Bastian, an artist and engineer, took on the challenge of creating the open-source SLS printer. He designed an integrated, high-precision z-axis and powder-handling system and fitted it with open-source, 3D printer electronics. He even used the machine’s laser-cutting features to produce many of the acrylic parts for the powder-handling system.
By the time Bastian left Rice in the fall of 2013, the researchers had demonstrated “proof of concept,” Miller said, “but a great deal of additional work still needed to be done to show that OpenSLS could be useful for bioengineering, and that is what Ian and the rest of the team accomplished.” Kinstlinger’s tests with PCL, a biocompatible plastic, which can be used in medical implants for humans, were particularly important.
Kinstlinger explained that the increased surface area on rough surfaces and in interconnected pore structures are preferable in certain situations, while other biological applications call for smooth surfaces. He 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 five-minute time periods, which provided a very smooth surface, due to surface-tension effects. (See Figure 1)
For more information, visit http://news.rice.edu . Video can be viewed at www.techbriefs.com/tv/OpenSLS.
