Arranging fibers just like nature does it
Nature has produced exquisite composite materials--wood, bone, teeth, and shells, for example--that combine light weight and density with desirable mechanical properties such as stiffness, strength and damage tolerance.
Rotational 3-D printing precisely choreographs the speed and rotation of a 3-D printer nozzle to program the arrangement of embedded fibers in polymer matrices. This is achieved by equipping a rotational printhead system with a stepper motor to guide the angular velocity of the rotating nozzle as the ink is extruded.
Credit: Brett Compton/SEAS
Since ancient civilizations first combined straw and mud to form bricks, people have fabricated engineered composites of increasing performance and complexity. But reproducing the exceptional mechanical properties and complex microstructures found in nature has been challenging.
Now, a team of researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) has demonstrated a novel 3D printing method that yields unprecedented control of the arrangement of short fibers embedded in polymer matrices. They used this additive manufacturing technique to program fiber orientation within epoxy composites in specified locations, enabling the creation of structural materials that are optimized for strength, stiffness, and damage tolerance.
Their method, referred to as "rotational 3D printing," could have broad ranging applications. Given the modular nature of their ink designs, many different filler and matrix combinations can be implemented to tailor electrical, optical, or thermal properties of the printed objects.
"Being able to locally control fiber orientation within engineered composites has been a grand challenge," said the study's senior author, Jennifer A. Lewis, Hansjorg Wyss Professor of Biologically Inspired Engineering at Harvard SEAS. "We can now pattern materials in a hierarchical manner, akin to the way that nature builds." Lewis is also a Core Faculty Member of the Wyss Institute for Biologically Inspired Engineering at Harvard.
The work, described in the journal PNAS, was carried out in the Lewis lab at Harvard. Collaborators included then-postdoctoral fellows Brett Compton (now Assistant Professor in Mechanical Engineering at the University of Tennessee, Knoxville), and Jordan Raney (now Assistant Professor of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania); and visiting PhD student Jochen Mueller from Prof. Kristina Shea's lab at ETH Zurich.
The key to their approach is to precisely choreograph the speed and rotation of a 3D printer nozzle to program the arrangement of embedded fibers in polymer matrices. This is achieved by equipping a rotational printhead system with a stepper motor to guide the angular velocity of the rotating nozzle as the ink is extruded.
"Rotational 3D printing can be used to achieve optimal, or near optimal, fiber arrangements at every location in the printed part, resulting in higher strength and stiffness with less material," Compton said. "Rather than using magnetic or electric fields to orient fibers, we control the flow of the viscous ink itself to impart the desired fiber orientation."
Compton noted that the team's nozzle concept could be used on any material extrusion printing method, from fused filament fabrication, to direct ink writing, to large-scale thermoplastic additive manufacturing, and with any filler material, from carbon and glass fibers to metallic or ceramic whiskers and platelets.
The technique allows for the 3D printing of engineered materials that can be spatially programmed to achieve specific performance goals. For example, the orientation of the fibers can be locally optimized to increase the damage tolerance at locations that would be expected to undergo the highest stress during loading, hardening potential failure points.
"One of the exciting things about this work is that it offers a new avenue to produce complex microstructures, and to controllably vary the microstructure from region to region," Raney said. "More control over structure means more control over the resulting properties, which vastly expands the design space that can be exploited to optimize properties further."
"Biological composite materials often have remarkable mechanical properties: high stiffness and strength per unit weight and high toughness. One of the outstanding challenges of designing engineering materials inspired by biological composites is control of fiber orientation at small length scales and at the local level," said Lorna J. Gibson, Professor of Materials Science and Engineering at MIT, who was not involved in the research. "This remarkable paper from the Lewis group demonstrates a way of doing just that. This represents a huge leap forward in the design of bio-inspired composites."
The Harvard Office of Technology Development has protected the intellectual property relating to this project.
Previously, Lewis has conducted groundbreaking research in the 3D printing of tissue constructs with vasculature, lithium-ion microbatteries, and the first autonomous, entirely soft robot.
Other contributors to the paper include Thomas Ober from Harvard SEAS and Kristina Shea from ETH Zurich.
The research was supported by the Office of Naval Research and GETTYLAB.
Paul Karoff | EurekAlert!
Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern
20.07.2018 | Princeton University
Relax, just break it
20.07.2018 | DOE/Argonne National Laboratory
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences