The lattice, known as graphene, is made of pure carbon and appears under magnification like chicken wire. Because of its unique optical, electrical and mechanical properties, graphene is used in electronics, energy storage, composite materials and biomedicine.
This is crumpled graphene.
Credit: Xuanhe Zhao
However, graphene is extremely difficult to handle in that it easily "crumples." Unfortunately, scientists have been unable to control the crumpling and unfolding of large-area graphene to take advantage of its properties.
Duke engineer Xuanhe Zhao, assistant professor in Duke's Pratt School of Engineering, likens the challenge of controlling graphene to the difference between unfolding paper and wet tissue.
"If you crumpled up normal paper, you can pretty easily flatten it out," Zhao said. "However, graphene is more like wet tissue paper. It is extremely thin and sticky and difficult to unfold once crumpled. We have developed a method to solve this problem and control the crumpling and unfolding of large-area graphene films."
The Duke engineers attached the graphene to a rubber film that had been pre-stretched to many times its original size. Once the rubber film was relaxed, parts of the graphene detached from the rubber while other parts kept adhering to it, forming an attached-detached pattern with a feature size of a few nanometers. As the rubber relaxed, the detached graphene was compressed to crumple. But as the rubber film was stretched back, the adhered spots of graphene pulled on the crumpled areas to unfold the sheet.
"In this way, the crumpling and unfolding of large-area, atomic-thick graphene can be controlled by simply stretching and relaxing a rubber film, even by hands," Zhao said.
The results were published online in the journal Nature Materials.
"Our approach has opened avenues to exploit unprecedented properties and functions of graphene," said Jianfeng Zang, a postdoctoral fellow in Zhao's group and the first author of the paper. "For example, we can tune the graphene from being transparent to opaque by crumpling it, and tune it back by unfolding it."
In addition, the Duke engineers layered the graphene with different polymer films to make a "soft" material that can act like muscle tissues by contracting and expanding on demand. When electricity is applied to the graphene, the artificial muscle expands in area; when the electricity is cut off, it relaxes. Varying the voltage controls the degree of contraction and relaxation.
"The crumpling and unfolding of graphene allows large deformation of the artificial muscle," Zang said.
"New artificial muscles are enabling diverse technologies ranging from robotics and drug delivery to energy harvesting and storage," Zhao said. "In particular, they promise to greatly improve the quality of life for millions of disabled people by providing affordable devices such as lightweight prostheses and full-page Braille displays."
Zhao's work is supported by the National Science Foundation's (NSF) Triangle Materials Research Science and Engineering Center, NSF Materials and Surface Engineering program, and National Institutes of Health (NIH). Other members of the team are Duke's Qiming Wang and Qing Tu.
Richard Merritt | EurekAlert!
Move over, Superman! NIST method sees through concrete to detect early-stage corrosion
27.04.2017 | National Institute of Standards and Technology (NIST)
Control of molecular motion by metal-plated 3-D printed plastic pieces
27.04.2017 | Ecole Polytechnique Fédérale de Lausanne
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
27.04.2017 | Earth Sciences
27.04.2017 | Materials Sciences
27.04.2017 | Materials Sciences