Tag Archives: Yang Gao

Bulletproof graphene

A December 18, 2017 news item on Nanowerk announces research that demonstrates graphene can be harder than diamonds (Note: A link has been removed),

Imagine a material as flexible and lightweight as foil that becomes stiff and hard enough to stop a bullet on impact. In a newly published paper in Nature Nanotechnology (“Ultrahard carbon film from epitaxial two-layer graphene”), researchers across The City University of New York (CUNY) describe a process for creating diamene: flexible, layered sheets of graphene that temporarily become harder than diamond and impenetrable upon impact.

Scientists at the Advanced Science Research Center (ASRC) at the Graduate Center, CUNY, worked to theorize and test how two layers of graphene — each one-atom thick — could be made to transform into a diamond-like material upon impact at room temperature. The team also found the moment of conversion resulted in a sudden reduction of electric current, suggesting diamene could have interesting electronic and spintronic properties. The new findings will likely have applications in developing wear-resistant protective coatings and ultra-light bullet-proof films.

A December 18, 2017 CUNY news release, which originated the news item, provides a little more detail,

“This is the thinnest film with the stiffness and hardness of diamond ever created,” said Elisa Riedo, professor of physics at the ASRC and the project’s lead researcher. “Previously, when we tested graphite or a single atomic layer of graphene, we would apply pressure and feel a very soft film. But when the graphite film was exactly two-layers thick, all of a sudden we realized that the material under pressure was becoming extremely hard and as stiff, or stiffer, than bulk diamond.”

Angelo Bongiorno, associate professor of chemistry at CUNY College of Staten Island and part of the research team, developed the theory for creating diamene. He and his colleagues used atomistic computer simulations to model potential outcomes when pressurizing two honeycomb layers of graphene aligned in different configurations. Riedo and other team members then used an atomic force microscope to apply localized pressure to two-layer graphene on silicon carbide substrates and found perfect agreement with the calculations. Experiments and theory both show that this graphite-diamond transition does not occur for more than two layers or for a single graphene layer.

“Graphite and diamonds are both made entirely of carbon, but the atoms are arranged differently in each material, giving them distinct properties such as hardness, flexibility and electrical conduction,” Bongiorno said. “Our new technique allows us to manipulate graphite so that it can take on the beneficial properties of a diamond under specific conditions.”

The research team’s successful work opens up possibilities for investigating graphite-to-diamond phase transition in two-dimensional materials, according to the paper. Future research could explore methods for stabilizing the transition and allow for further applications for the resulting materials.

There’s an artist’s representation of a bullet’s impact on graphene,

By applying pressure at the nanoscale with an indenter to two layers of graphene, each one-atom thick, CUNY researchers transformed the honeycombed graphene into a diamond-like material at room temperature. Photo credit: Ella Maru Studio Courtesy: CUNY

Here’s a link to and a citation for the paper,

Ultrahard carbon film from epitaxial two-layer graphene by Yang Gao, Tengfei Cao, Filippo Cellini, Claire Berger, Walter A. de Heer, Erio Tosatti, Elisa Riedo, & Angelo Bongiorno. Nature Nanotechnology (2017) doi:10.1038/s41565-017-0023-9 Published online: 18 December 2017

This paper is behind a paywall.

University of Alberta (Canada) student nanorobotics team demonstrates potential medical technology in competitiion

A University of Alberta (Canada) nanorobotics team has entered its nanobot system into the International Mobile Micro/nanorobotics Competition in Karlsruhe, Germany, as part of the ICRA Robot Challenges at the IEEE (Institute of Electrical and Electronics Engineers) International Conference on Robotics and Automation (ICRA) being held May 6 – 10, 2013 in Karlsruhe, Germany. From the May 6, 2013 news item on Nanowerk,

A team of engineering students is putting a twist on robotics, developing a nano-scale robotics system that could lead to new medical therapies.

In less than a year, the U of A team has assembled a working system that manipulates nano-scale ‘robots’. The team uses magnets to manipulate a droplet filled with iron oxide nanoparticles. Barely visible to the naked eye, the droplet measures 400-500 micrometres.

The May 3, 2013 University of Alberta news release by Richard Cairney, which originated the news item, describes the system,

Using a joystick, team members control the robot, making it travel along a specific route, navigate an obstacle course or to push micro-sized objects from one point to another.

The challenge is simple in concept but highly technical and challenging to execute: the team first injects a water droplet with iron oxide nanoparticles into into oil. The droplet holds its shape because it is encased in a surfactant—a soap-like formula that repels water on one side and attracts water on the other.

“It’s like a capsule,” said team member Yang Gao, who is working on her master’s degree in chemical engineering. “It’s a vehicle for the nanoparticles.”

The iron-filled droplet is placed in a playing ‘field’ measuring 2 x 3 millimetres. The team uses four magnets mounted each side of the rectangular field to move the droplet in a figure-8, manoeuvring it through four gates built into the field.

“We use the magnets to pull the droplet,” explains electrical engineering PhD student Remko van den Hurk.

In a second challenge, the team will be required to use the droplet as a bulldozer of sorts, to arrange micro-scale objects that measure 200 x 300 micrometres into a particular order on an even smaller playing field.

The competition has its serious side, these nanobots could one day be used in medical applications.

In the meantime there’s the competition, good luck!