Graphene has been the subject of many studies due to its unusual properties, especially its strength. The material is thought to be the strongest of all known materials. However, researchers have had a hard time translating the strength of 2D graphene—basically a flat sheet that is just one atom in thickness—into useful, 3D structures.
A recent study from MIT proves it can be done. The team compressed and fused flakes of graphene into stable 3D structures using a combination of high pressure and heat. The shapes that formed had an enormous surface area in proportion to their volume and were extraordinarily strong: One sample had 5% the density of steel, but 10 times the strength.
The MIT team also discovered that when they compressed the graphene, the resulting geometric shape that formed resembled some corals and microscopic creatures called diatoms. The graphene naturally became round and porous and formed a gyroid shape. Markus Buehler, the head of MIT’s Department of Civil and Environmental Engineering and one of the study’s authors, said that actually making these gyroid shapes using conventional manufacturing processes is “probably impossible.”
In fact, the geometric shape proved even more important than the material. The unusual geometrical configuration could also be made with similar strong, lightweight materials, opening up the possibility of many applications.
For instance, concrete for large-scale structures like bridges could be made with this porous geometry. Because the shape is riddled with very tiny pore spaces, the material might also find application in some filtration systems, for either water or chemical processing.
“You could either use the real graphene material or use the geometry we discovered with other materials, like polymers or metals,” Buehler said. “You can replace the material itself with anything. The geometry is the dominant factor. It’s something that has the potential to transfer to many things.”
The researchers examined the geometric structure of these gyroid shapes further by creating 3D-printed plastic models and subjected them to various tests, including tensile and compression tests. Computational simulations the group conducted showed that one of the sample shapes had 5% the density of steel, but 10 times the strength. The results from the experiments and computational simulations matched accurately.
“The combination of computational modeling with 3D-printing-based experiments used in this paper is a powerful new approach in engineering research. It is impressive to see the scaling laws initially derived from nanoscale simulations resurface in macroscale experiments under the help of 3D printing,” said Huajian Gao, a professor of engineering at Brown University, who was not involved in this work.
The research was supported by the Office of Naval Research, the Department of Defense Multidisciplinary University Research Initiative, and BASF-North American Center for Research on Advanced Materials and was published in the journal Science Advances.
Soft robotic sleeve helps a beating heart
Researchers at Harvard University and Boston Children’s Hospital developed a soft robotic sleeve that fits around a heart and augments cardiovascular functions weakened by heart failure. The development has the potential to greatly expand treatment options for those suffering from the disease.
The soft robotic sleeve takes inspiration from the heart itself. It uses pneumatic actuators that twist and compress around the heart, mimicking the organ’s natural outer muscle layers. The sleeve is attached to the heart using a combination of a suction device, sutures and a gel interface to help with friction between the device and the heart. The device is tethered to an external pump, which uses air as a power source.
Currently, ventricular assist devices (VADs), which pump blood from the ventricles into the aorta, are used to treat heart failure. A major difference between VADs and the soft robotic sleeve is that the sleeve doesn’t directly come into contact with blood. Patients using VADs are at a greater risk for blood clots and stroke. The soft robotic sleeve reduces this risk and eliminate the need for patients to take blood thinner medications.
The robotic sleeve is customizable. The actuators can be tuned to give more assistance on one side of the heart, if the patient is weaker on one side. The pressure can also increase or decrease over time depending on the patient’s progress.
“The cardiac field had turned away from idea of developing heart compression instead of blood-pumping VADs due to technological limitations. But now, with advancements in soft robotics, it’s time to turn back,” said Frank Pigula, a cardiothoracic surgeon and co-corresponding author on the study. “Most people with heart failure do still have some function left. One day the robotic sleeve may help their heart work well enough that their quality of life can be restored.”
Researchers tested the device on animal models. And while it isn’t quite ready for use in humans, Harvard’s Office of Technology Development has filed a patent application and is pursuing commercialization opportunities.
The research, published in Science Translational Medicine, was a collaboration between the Harvard John A. Paulson School of Engineering and Applied Sciences, The Wyss Institute of Biologically Inspired Engineering at Harvard, and Boston Children’s Hospital.
Getting closer to devices that convert heat to power
Engineers from The Ohio State University who previously pioneered the use of a quantum mechanical effect to convert heat into electricity adapted their research for industrial applications.
The study, published in the journal Nature Communications, describes how the OSU researchers used magnetism on a nickel-platinum composite to amplify the voltage output by 10 times or more. By distributing a small amount of platinum nanoparticles randomly throughout the nickel, the resulting composite produced the enhanced voltage due to the Seebeck effect. This means that, for a given amount of heat, the composite material generated more electrical power than either material could on its own.
In related research from the same group, published in 2012, the platinum was applied on top of a magnetic material in a thin film. That study showed that magnetic fields boosted the Seebeck effect, and boosted the voltage output of the thin film from a few microvolts to a few millivolts.
The group’s latest research uses a thicker piece of material that more closely resembles components in electronic devices. Since the entire piece of composite is electrically conducting, other electrical components can draw the voltage from it with increased efficiency compared with a film. The 2012 study also used exotic nano-structured materials for the film, instead of the two common and accessible metals used in the present-day study. The voltage output is smaller—measured in nanovolts instead of the microvolts and millivolts of the earlier study—but the device is much simpler, requiring no nanofabrication and able to be easily scaled up for industry.
The study is part of a growing area of research called solid-state thermoelectrics. Solid-state thermoelectrics aims to capture “waste heat”—heat that’s a normal byproduct of numerous electrical and mechanical devices, such as a car engine—and use it as an energy source.
“Over half of the energy we use is wasted and enters the atmosphere as heat,” Stephen Boona, a co-author of the study, said. “Solid-state thermoelectrics can help us recover some of that energy. These devices have no moving parts, don’t wear out, are robust and require no maintenance. Unfortunately, to date, they are also too expensive and not quite efficient enough to warrant widespread use. We’re working to change that.”
While the composite isn’t yet part of a real device, the group hopes its study will inspire further research that will lead to applications for common waste heat generators.
The research was funded by the National Science Foundation’s Materials Research Science and Engineering Program and the US Army’s Multidisciplinary University Research Initiative.
Robotics institute latest to join Manufacturing USA
Carnegie Mellon University formed a nonprofit venture called American Robotics in Pittsburgh, and it will lead The Advanced Robotics Manufacturing (ARM) Institute that the Obama administration formed in January.
The institute has a four-pronged mission:
• empower American workers to compete with low-wage workers abroad;
• create and sustain new jobs to secure US national prosperity;
• lower the technical, operational, and economic barriers for small- and medium-sized enterprises, as well as large companies to adopt robotics technologies, and
• assert US leadership in advanced manufacturing.
The institute’s activities will be funded by $80 million from the Department of Defense and $173 million from partner organizations.
The institute includes a national network of 231 stakeholders from industry, academia, local governments and nonprofits. Some of the robotics technologies the institute will focus on are collaborative robotics; robot learning, adapting, and repurposing; dexterous manipulation; autonomous navigation and mobility, and perception and sensing.
ARM’s 10-year goals include increasing worker productivity by 30%, creating 510,000 new manufacturing jobs in the US, ensuring that 30% of small and medium-sized enterprises adopt robotics technology, and providing the ecosystem where major industrial robotics manufacturers will emerge.
Gary Fedder, vice provost for research at Carnegie Mellon University, is the interim CEO of The ARM Institute.
The Manufacturing USA network is a bipartisan program that brings together industry, academia and government to co-invest in the development of world-leading manufacturing technologies and capabilities.
MIT researchers used 3D-printed gyroid models like this one to test the strength and mechanical properties of a new lightweight material.
Harvard researchers developed a customizable soft robot that fits around a heart and helps it beat, potentially opening new treatment options for people suffering from heart disease. The device is tethered to an external pump, which uses air to power the soft actuators
A scanning transmission electron microscope image of a nickel-platinum composite material created at Ohio State University. At left, the image is overlaid with false-color maps of elements in the material, including platinum (red), nickel (green) and oxygen (blue). Imaging by Isabel Boona, OSU Center for Electron Microscopy and Analysis; Left image prepared by Renee Ripley.