From Scratch: Taking 3D Printing Technology to the Next Level
“Repairing injuries to the skin and bones of the skull is particularly challenging given the many layers of different tissue types involved,” he said. “Trying to work with these two materials at the same time is an even greater challenge.”
Currently, he explained, repairing injuries to the skull requires the use of skin and bone from another part of the patient’s body, which requires additional surgery, or from a cadaver, which risks being rejected by the patient’s immune system. For their study, Ozbolat and his colleagues instead created printable bone material using a mixture of collagen; chitosan, a sugar from the outer skeleton of shellfish; nano-hydroxyapatite, a component of tooth enamel; and bone morphogenetic protein-2, an FDA-approved growth factor for bone regeneration. For the skin, they used collagen and fibrinogen, a protein made in the liver that helps blood clot.
After accurately scanning the defect in the rat’s skull, Ozbolat explained, the 3D printer followed the 3D “blueprint”, extruding bone material onto the wound, followed by barrier material, then skin material. The whole process took less than five minutes. After repairing the 6 millimeter wide hole in the skin and the 5 millimeter wide hole in the bone separately, they moved on to repairing both in the same surgery. “There is no surgical method to repair soft and hard tissue at the same time,” Ozbolat noted.
The next step, he said, is to add compounds that can help facilitate vascularization, since blood flow to bones is especially important for healing. He and his team are already working with neurosurgeons, craniomaxillofacial surgeons and plastic surgeons at Penn State Hershey Medical Center to translate this research into human applications.
In addition to repairing skin and bones, Ozbolat and his team are using 3D bioprinting to help study breast cancer. In a recent study, the team generated tumor models, called tumor spheroids, to study how a tumor cell’s distance from neighboring endothelial cells – cells that line the walls of blood vessels – and fibroblasts – cells connective tissue – influences its ability to grow. The closer a tumor cell is to an endothelial cell or fibroblast, they found, the more aggressively it is likely to spread.
“In research like this, it is important to maintain the precision of the variables being tested,” said Madhuri Dey, a PhD student in chemistry. “In this project, 3D printing allows us to precisely adjust the position of the tumor relative to the main blood vessel in order to observe the effects of distance on tumor growth. Using a natural tumor would introduce too much variability.
Printing with concrete
While 3D printing of biological materials has the potential to transform healthcare, the technique may also redesign how we design and build our living structures – not just on Earth, but perhaps even in space.
Recently, Jose Duarte, Stuckeman Chair in Design Innovation, and Shadi Nazarian, Associate Professor of Architecture, co-led an interdisciplinary team of students and faculty that won second place in a NASA competition. The goal? Designing an autonomous system capable of creating a human shelter on Mars using 3D printing technology. With their input, the team succeeded in building the world’s first fully 3D-printed structure to include a roof built in place without formwork or molds, Duarte said.
“The other teams printed the roof separately and then either raised it in its place, or else used formwork to prevent it from collapsing during printing,” Duarte added.
Duarte credited Sven Bilén, professor of engineering design, technology, and professional programs, for his unique contribution to the printing system. “Sven added an ingenious extension to the robotic arm that allowed him to reach far enough to print the entire structure, increasing what we call ‘design freedom’,” Duarte said.
Another competition challenge was to 3D print with a specialized concrete capable of withstanding extreme environmental conditions as a finished structure. Aleksandra Radlinska, associate professor of civil engineering, brought to the team her expertise in the behavior of cement and concrete. 3D printing with concrete can be tricky, Radlinska explained, because the mixture must be fluid enough to be extruded through a print nozzle, but then stable and strong enough to support additional layers. When done right, researchers have shown that 3D printing with concrete can result in structures that are as strong as traditionally built ones, while using less material.