Modified Laser Cutter Prints 3D Objects from Powder

Researchers in the Miller Lab at Rice University’s Department of Bioengineering used a commercial-grade CO2 laser cutter to create OpenSLS, an open-source, selective laser sintering platform that can print intricate 3D objects from powdered plastics and biomaterials. (Source: J. Fitlow, Rice University)

Researchers in the Miller Lab at Rice University’s Department of Bioengineering used a commercial-grade CO2 laser cutter to create OpenSLS, an open-source, selective laser sintering platform that can print intricate 3D objects from powdered plastics and biomaterials. (Source: J. Fitlow, Rice University)

Rice University bioengineering researchers have modified a commercial-grade CO2 laser cutter to create OpenSLS, an open-source, selective laser sintering platform that can print intricate 3D objects from powdered plastics and biomaterials.

“SLS technology … is 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 at Rice 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.”

“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 team showed that the machine could print a series of intricate objects from both nylon powder and from polycaprolactone, or PCL, a nontoxic polymer that’s commonly used to make templates for studies on engineered bone.

“In terms of price, OpenSLS brings this technology within the reach of most labs, and our goal from the outset has been to do this in a way that makes it easy for other people to reproduce our work and help the field standardize on equipment and best practices,” Kinstlinger said. “We’ve open-sourced all the hardware designs and software modifications and shared them via Github.”

“The cutter’s laser is already in the correct wavelength range – around 10 µm – and the machines come with hardware to control laser power and the x-axis and y-axis with high precision,” Miller said. 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 from Ultimachine.com. Miller said Bastian even used the machine’s laser-cutting features to produce many of the acrylic parts for the powder-handling system.

“You can actually cut most of the required parts with the same laser cutter you are in the process of upgrading,” Miller said. “It’s around $2,000 in parts to build OpenSLS, and adding the parts to an existing laser cutter and calibrating the machine typically takes a couple of days.” By the time Bastian left Rice in the fall of 2013, “we 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.”

Unlike most commercial SLS platforms, Rice University’s OpenSLS allows researchers to work with their own powdered materials, including specialized biomaterials like polycaprolactone, or PCL, a common nontoxic polymer that was used to print these tissue-engineering scaffolds. Researcher Ian Kinstlinger developed a method for smoothing the surfaces (left) of newly printed scaffolds (right) using vaporized solvent. (Source: J. Fitlow, Rice University)

Unlike most commercial SLS platforms, Rice University’s OpenSLS allows researchers to work with their own powdered materials, including specialized biomaterials like polycaprolactone, or PCL, a common nontoxic polymer that was used to print these tissue-engineering scaffolds. Researcher Ian Kinstlinger developed a method for smoothing the surfaces (left) of newly printed scaffolds (right) using vaporized solvent. (Source: J. Fitlow, Rice University)

Miller said Kinstlinger’s tests with PCL, a biocompatible plastic that can be used in medical implants for humans, were particularly important. “Biology in the body can take advantage of architectural complexity in 3D parts, but different shapes and surfaces are useful under different circumstances,” Miller said. For example, Kinstlinger said, 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.

Kinstlinger addressed each possibility with PCL by developing an efficient way to smooth the rough surfaces of PCL objects that came out of the printer. He found that exposing the parts to solvent vapor for short time periods (around 5 minutes) 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 – Kinstlinger 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,” he said.

Miller said, “Our work demonstrates that OpenSLS provides the scientific community with an accessible platform for the study of laser sintering and the fabrication of complex geometries in diverse plastics and biomaterials. And it’s another win for the open-source community.” (Source: Rice U.)

Link: Physiologic Systems Engineering and Advanced Materials Laboratory, Dept. Bioengineering, George R. Brown School of Engineering, Rice University, Houston, Texas, USA

Reference: I. Kinstlinger et al.: Open-Source Selective Laser Sintering (OpenSLS) of Nylon and Biocompatible Polycaprolactone, PLOS one; DOI: 10.1371/journal.pone.0147399

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