Jim Stasiak and Pallavi Dhagat inspect samples of devices created with their digital inkjet printer.
“I have a vison of printing an entire robot that would walk off the printer,” said Pallavi Dhagat, professor of electrical and computer engineering at Oregon State University and president of the IEEE Magnetics Society.
She and collaborators at the University of Oregon and HP Labs, the exploratory and advanced research group for HP Inc., are taking the initial step toward making that distant vision a reality — figuring out how to print electric and magnetic devices. In a project funded by the National Science Foundation, the first milestone will be the ability to print devices such as sensors or antennas. But the bigger goal is to lay the foundation for fabricating complete objects with both functional and structural components. In the process, these researchers are driving the emerging field of digital materials science.
In the same way a standard inkjet printer mixes color, Dhagat and her colleagues’ experimental printer uses inks composed of dielectric and magnetic nanoparticles to digitally print materials with tailored electromagnetic properties. If it proves successful, device designers will have the ability to print custom devices for very specific applications.
This novel printing capability will also accelerate the development of new technologies by enabling rapid prototyping and optimization. “Just like when you are designing a graphic and print several versions to see what it looks like, a device designer could test out each new tweak in the design,” Dhagat said. “That’s the beauty of this.”
Forging this new field of digital materials science has not been easy. It started over 20 years ago, when Jim Stasiak, distinguished technologist at HP Labs and an expert in advanced printing technology, began collaborating with materials scientists at Oregon State. The initial research was with John Wager, professor emeritus of electrical and computer engineering, and Douglas Keszler, distinguished professor of chemistry.
This fundamental work began with experiments that provided proof that it was possible to fabricate simple devices using digital inkjet printing methods. The current collaboration builds upon these achievements using a fabrication method based on HP’s new Multi Jet Fusion 3D printing technology. The method makes it possible to sequentially print individual layers of material with precisely determined magnetic properties.
“The biggest challenge for us has been getting enough of the magnetic or dielectric particles in the ink to be useful,” Dhagat said. “Dielectric inks have been investigated more extensively, but we are one of the few groups around the world to be looking at printing magnetic materials.”
Wrestling with this challenge has driven innovations in both materials science and printing technology. The first step is simply creating the ink. For this, Dhagat turned to longtime collaborator James Hutchison, Lokey-Harrington Chair in the Department of Chemistry and Biochemistry at the University of Oregon. He and his research team have been designing the nanoparticles and the fluid carrier, or matrix, for the ink.
“There are a lot of details to consider in the ink formulation,” Dhagat said. “It’s not trivial at all.”
For example, the nanoparticles need to be small enough and remain dispersed in the ink so they do not clog the nozzle of the print head. The matrix has to have the right chemical and fluidic properties to be jettable. The HP team has contributed expertise in formulating and optimizing stable nanoparticle-bearing inks.
Dhagat and Stasiak, meanwhile, have been working on the printing techniques, particularly with magnetic inks for which there are few published results to go by. After a layer of the magnetic ink is printed, a magnetic field is applied to orient and align the nanoparticles’ magnetic north and south poles. Then the ink is cured with ultraviolet radiation so the oriented particles are fixed. Although this method has been successful in producing material with magnetic properties, the magnetic strength is less than what is required for device applications.
Throughout the development of the project, several graduate and undergraduate students at both universities have contributed pieces to this complicated puzzle, while gaining valuable research experience with an industry partner. Currently, Stasiak and Dhagat are advising Madeleine Cannamela, a master’s student in materials science and an HP intern. For her thesis work, she will adapt and extend the Multi Jet Fusion printing process to fabricate materials with better physical and magnetic properties.
Stasiak says his collaborations over the years with Oregon State and the University of Oregon have been both productive and intellectually rewarding.
“Each organization brings unique capabilities and resources to the project that, when combined, have led to remarkable discoveries and advances in many different technology domains,” Stasiak said.
To fully achieve Dhagat’s vison of a robot walking off the printer it will take a community of researchers combining their knowledge in this new field of digital materials science.
“It’s a big goal,” Dhagat said. “Right now we are just trying to solve the first few steps, but as we are running into challenges, we are understanding all the different pieces that have to come together.”
by Rachel Robertson
MOMENTUM, College of Engineering, Fall 2019
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