From the ground up: Taking 3D printing technology to the next level

A support bath used for supporting the structural integrity of printed tissues, enabling printing with anatomical complexities. Credit: Patrick Mansell / Penn State. Creative Commons

March 21, 2022

By Sara LaJeunesse

Timothy Simpson is the proud owner of a custom wristwatch, one of only a few made entirely in the United States these days. Created by Vortic Watch Company, a firm owned by Penn State alumnus R.T. Custer, the piece is a beautiful 1908 pocket watch made in Waltham, Massachusetts, that is encased in a 3D-printed titanium outer shell and fitted with a custom leather strap.

With 3D printing, "Vortic was able to give new life to an antique, and create a niche high-end luxury good," said Simpson, interim department head of the School of Engineering Design, Technology, and Professional Programs and the Paul Morrow Professor in Engineering Design and Manufacturing.

A big part of the technology's appeal, Simpson added, is that it allows for a level of customization not possible with traditional manufacturing. With 3D printing, Vortic can create custom titanium fittings for each unique timepiece using the same machine and placing orders after receiving payment. For Custer and a growing number of others, 3D printing has lowered barriers to manufacturing.

"It democratizes entrepreneurship, especially for hardware-based startups," said Simpson. "Entrepreneurs don't have to invest millions of dollars in machines and equipment. They can just buy a couple of printers and start making things."

"From a capability standpoint, we are among the top institutions in the world in additive manufacturing."

Tim Simpson, Paul Morrow Professor in Engineering Design and Manufacturing

Indeed, for about $150, anyone can walk out of a Walmart with a 3D printer capable of creating a growing array of tools, toys, and other trinkets. In recent years, however, the technique has grown considerably more sophisticated; its products moving beyond just bits and bobs made of plastic to include high-tech items fabricated from metal, concrete, clay, and even biomaterials. Researchers at Penn State are at the leading edge of the field now known as additive manufacturing, working to advance the capabilities of 3D printing with a goal of addressing pressing problems in human health, housing, and transportation, among other areas.

A different ballgame

"Anyone can buy a printer, learn how to put material in it, and hit go, but designing parts that really take advantage of 3D printing — so they are better, faster, and cheaper than traditionally made components — is another ballgame," said Simpson. "You have to understand the economics, the materials, the design, the process. It's a contact sport; you have to rub shoulders and talk to experts in a lot of other disciplines to really do additive well."

The ability of Penn State's researchers to do just that — collaborate with colleagues across disciplines to address every component of a problem and its solution — is a strength of the University, Simpson said. "Because of this," he added, "from a capability standpoint, we are among the top institutions in the world in additive manufacturing, and we continue to expand into new areas as a result."

The term additive manufacturing, Simpson explained, describes the use of 3D printing to make functional components in a manufacturing setting. The process is "additive" because it produces an object by building it up one layer at a time. "Think of water dripping from the ceiling of a cave and depositing thin layers of minerals to form stalagmites on the cave floor," he said. By contrast, subtractive manufacturing creates components by removing material until the final part is complete. The additive process, by its nature, is both more flexible and far less wasteful.

Directed energy deposition additive manufacturing experiments explore the impact of pulsed laser processing on material microstructure and properties. Credit: Jason Bolt, ARL, Penn State. All Rights Reserved.

The process begins with a 3D model: a computer-aided design (CAD) representation of the object that specifies precisely how much material — plastic, metal, clay, or some other substance — needs to be deposited, and where. As the 3D printer reads its instructions, it extrudes a plastic filament from a nozzle onto the print bed in the specified manner or a laser melts metallic powder layer by layer to form a part. After completing the base layer, the printer adds additional layers until the item is complete.

In this way, users can print almost anything they can imagine. "We’re using 3D printing to make car and airplane parts, hip and knee implants, you name it," said Simpson. "Several years ago, there was an episode of 'Grey's Anatomy' where doctors reconstructed a patient's ear by growing a new one. We can do that now. This is actually happening, and Penn State has some of the leading experts in the field of 3D printing."

Printing with biomaterials

Imagine yourself a patient in an MRI machine. Likely you’re familiar with the concept of lying motionless within that snug tunnel as rotating scanners produce fine-grained images of your tissues and internal organs. Now imagine that such a machine could directly repair these tissues by depositing new layers of muscle or skin, even creating and installing new organs. Such is the dream of Ibrahim T. Ozbolat, associate professor of engineering science and mechanics, biomedical engineering and neurosurgery. Ozbolat is using 3D printing to create a range of materials for use in human health.

"I can envision a time when a patient might lie under a bioprinter and have new skin printed directly onto a wound," he said. Already, Ozbolat and his lab group have reported success in printing both bone and soft tissue onto the skulls of rats.

Miji Yeo, a postdoctoral fellow working in Ibrahim Ozbolat's lab, micro-valve bioprinting living cells for skin tissue fabrication Credit: Patrick Mansell / Penn State. Creative Commons

"Repairing injuries to the skin and bones of the skull is particularly difficult given the many layers of different types of tissues involved," he said. "Trying to work with these two materials at one time is an even greater challenge."

Currently, he explained, fixing skull injuries requires the use of skin and bone from another part of the patient's body, which requires additional surgery, or from a cadaver, which runs the risk of rejection by the patient's immune system. For their study, Ozbolat and his colleagues instead created a 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 aids in blood clotting.

After precisely scanning the rat's skull defect, Ozbolat explained, the 3D printer followed the 3D "blueprint," extruding the bone material onto the wound, followed by a barrier material, and then the skin material. The whole process took less than five minutes. After separately repairing the 6-millimeter-wide hole in the skin and the 5-millimeter-wide hole in the bone, they moved on to repair both during the same surgical procedure. "There is no surgical method for repairing soft and hard tissue at once," noted Ozbolat.

The next step, he said, is to add compounds that can help to facilitate vascularization, since blood flow to bone 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 to human applications.

In addition to repairing skin and bone, Ozbolat and his team are using 3D bioprinting to help in the study of breast cancer. In a recent study, the team generated tumor models, called tumor spheroids, to study how a tumor cell's distance from nearby endothelial cells — cells that line the walls of blood vessels — and fibroblasts — connective tissue cells — 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 precision in the variables that are being tested," said Madhuri Dey, a doctoral candidate in chemistry. "In this project, 3D printing allows us to precisely adjust the position of the tumor with respect to the main blood vessel so we can 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 capability to transform healthcare, the technique may also overhaul the way we design and build our living structures — not only 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 took second place in a NASA competition. The goal? To design an autonomous system capable of creating a human shelter on Mars using 3D-printing technology. With their entry, the team managed to build 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 raised it to its position afterward, or else used formwork to avoid its collapse during printing," added Duarte.

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 it to reach far enough to print the entire structure, thereby increasing what we call ‘design freedom,’" said Duarte.

Another challenge of the competition was to 3D print with a specialized concrete that can withstand extreme environmental conditions as a finished structure. Aleksandra Radlinska, associate professor of civil engineering, brought to the team her expertise in cement and concrete behavior. 3D printing with concrete can be tricky, Radlinska explained, because the mixture needs to be fluid enough to be extruded through a printing nozzle, but afterward stable and strong enough to support additional layers. When done right, researchers have shown, 3D printing with concrete can result in structures that are equally strong to those traditionally built, while using less material.

"You can build a large house with a small printer, one room at time. You can print the entire thing on site."

Jose Duarte, Stuckeman Chair in Design Innovation

Although the Mars shelter competition took place entirely on Earth, the team's final product could feasibly be built in space. The knowledge gained, however, will be used to create sustainable, low-cost housing options here, by simplifying and speeding up construction processes and saving on materials, Duarte said. He and his colleagues are already developing the technology to deploy structures in remote areas of Alaska, where temperature extremes rival those on Mars.

Coordinated by Ali Memari, Bernard and Henrietta Hankin Chair in Residential Building Construction, and with help from Ming Xiao, a professor of civil engineering, and Nathan Brown, a professor in architectural engineering, the team is designing an Alaska-ready 3D-printed model that includes a foundation, walls and a roof.

"The model is essentially a room, and you can combine rooms to build unique houses with a variety of configurations," said Duarte. "By doing this, you can build a large house with a small printer, one room at time. You can print the entire thing on site."

Printing with clay

Assistant Professor of Art Tom Lauerman is using 3D printing to build structures of another sort. Although much smaller in scale than a house, they are equally intriguing. And the material he is using — clay — can be found in his own backyard.

"As a sculptor, the medium I’ve worked with for many years is ceramics, but I’ve always been really interested in technology as well," said Lauerman. "So, I began learning 3D-modeling programs, like what an architect or industrial designer would use to design things. That was partly because it was an effective way for me to draw out ideas. I would make these 3D models basically as a blueprint for something that I would then go and try to make by hand."

As 3D printing advanced, Lauerman began to use the technology to make plastic molds, and from them to cast ceramic objects. "That worked really well," he said, "but it was time-consuming and cumbersome."

'Stairs' by Tom Lauerman, printed in terra cotta clay. The black surface is created using an ancient technique called 'terra sigillata' which translates to 'sealed earth'. Credit: Patrick Mansell / Penn State. Creative Commons

It was when Lauerman sought out Simpson for technical advice that the idea of 3D printing directly with clay was born. Because there were no off-the-shelf printers that suited his purpose, Lauerman, at Simpson's suggestion, went to the College of Engineering's Learning Factory to work with a team of students to build one.

The Bernard M. Gordon Learning Factory is a hands-on facility for engineering students to use in conjunction with capstone design and other courses. For the past five years, Lauerman has worked with these students to design and build custom 3D clay printers.

"The objects we were able to create at first were really crude; they were teeny, tiny little things," he said. Today, however, Lauerman's creations are much more sophisticated, and he is planning to display them in a formal exhibition in the coming year.

"3D printing allows me to experiment with nearly unlimited possibilities," he said. "I can make things with really intricate repeating patterns that would be very difficult to do by hand, and if I want to make a tiny tweak, I can do that without having to go through the immense effort of rebuilding from scratch."

Printing with metal

While biological materials, cement and clay are opening doors to exciting possibilities through 3D printing, Simpson said, "what's really supercharged additive manufacturing in the last 10 years is metals." The technology has developed to the point of allowing metal parts to be made with complex curves or cavities very difficult to achieve with subtractive processes, he explained. The results have already started to impact the manufacture of automobiles and airplanes, among other industries.

Simpson's colleague Edward "Ted" Reutzel is one of more than a dozen researchers in the Applied Research Laboratory at Penn State who are advancing metal 3D printing. Reutzel directs the Center for Innovative Materials Processing Through Direct Digital Deposition (CIMP-3D), an 8,000 square-foot facility located at Innovation Park whose cutting-edge capabilities and expertise allow it to serve as the Additive Manufacturing Demonstration Facility for the U.S. Defense Advanced Research Project Agency (DARPA). In the past 10 years, CIMP-3D has hosted more than 6,000 visitors, spun out three start-up companies, created more than 30 new jobs in the region, and supported the launch of the world's first additive manufacturing and design graduate program, which now enrolls over 200 industry practitioners from more than 80 different companies.

Ted Reutzel and Allison Beese discuss sample specimens of Ti-6Al-4V, a titanium alloy widely used in the aerospace industry, being fabricated in a laser powder bed fusion machine at the Center for Innovative Materials Processing Through Direct Digital Deposition (CIMP-3D) in Innovation Park. Credit: Jason Bolt, ARL, Penn State. All Rights Reserved.

Working with the U.S. Navy in 2016, Reutzel led a team that supported the U.S. Naval Air Systems Command in designing and building the world's first 3D-printed flight-critical component — a titanium link that helps to secure the engine to the frame of a Navy tiltrotor aircraft. Today, Reutzel and his colleagues at CIMP-3D are focused on additive manufacturing technology from early-stage research to applications for industrial use, and on helping to develop methods to efficiently assess and improve additive manufacturing part quality.

"Additive manufacturing has the potential to revolutionize manufacturing by providing on-demand production, decreasing material and manufacturing costs, allowing highly flexible designs for production, and producing features and material combinations that are not currently feasible," said Reutzel. But obstacles remain, he said — for one, the "lack of established quality control practices for built parts poses a challenge to wider adoption."

As Reutzel explained, the 3D printing process that enables rapid fabrication of complex parts is itself quite complex, and small process perturbations can be correlated to material defects such as voids or porosity — essentially holes in the material that are smaller than a human hair. These defects can lead to cracking and instability, jeopardizing durability and safety.

Reutzel and colleagues including Parisa Shokouhi, associate professor of engineering science and mechanics, are investigating various processes for identifying such defects, including nonlinear resonance ultrasonic spectroscopy, which can predict how long an object will last before failing, and X-ray computed tomography, which enables visualization of interior flaws within solid objects.

Allison Beese, associate professor of materials science and engineering and mechanical engineering, is also working toward quality control in metals. Beese, who directs Penn State's Additive Manufacturing & Design Graduate Program, focuses much of her research on functionally graded materials, which combine materials with different attributes to achieve desired properties.

"It's very exciting to be at the leading edge of the additive revolution."

Tim Simpson, Paul Morrow Professor in Engineering Design and Manufacturing

Beese also examines the relationships between temperature, microstructure, and mechanical properties related to the printing process. When additively manufacturing metals, for example, the raw material fed into the printer is often in the form of a metallic powder or wire feedstock. These materials are melted with a laser or electron beam, and as each layer of the desired object is added, it cools and solidifies and fuses to the layer below. This process introduces rapid heating and cooling cycles, resulting in microstructures within the material that differ drastically from those seen in cast or wrought counterparts. "To reliably use metals in structural applications, their mechanical properties must be understood and be predictable," said Beese. "My lab's work may ultimately aid in defining metrics for quality control and repeatability, and lead to the development of new materials."

While safety and quality are top priorities as more and more consumer and industrial products are manufactured this way, 3D printing with multiple materials is another promising area for future research. "If we want to print a house, currently we print the concrete, but leave spaces for the windows," Simpson explained. "Could we just switch to a transparent polymer during the process of putting in the concrete to get a window?"

The digital nature of additive manufacturing means that 5G, the next generation of wireless network technology, will create new opportunities for remote monitoring and operation, Simpson says. "Our hope is to build a 5G testbed on campus that will serve as a platform to develop, deploy, and test new protocols for additive manufacturing and other digital manufacturing technologies." With 5G in place, he said, "We can open up entirely new avenues for quality assurance and quality control."

From the custom watches that are already available to the artificial organs being tested for the future, 3D printing and additive manufacturing is allowing us to produce traditional products more affordably and sustainably and to create entirely new products that may transform the way we travel, build homes, and manage our health. At Penn State, researchers are using the technology in novel and exciting ways that are already impacting the world.

"Our faculty and students are working directly with industry to help solve real-world problems," said Simpson. "It's very exciting to be at the leading edge of the additive revolution at Penn State, and our ability to collaborate so easily strengthens our impact far beyond what any of us could do alone."

This story first appeared in the Fall 2021 issue of Research/Penn State magazine.

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