Tag Archives: Qian Wang

Improve car performance with graphene balls

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Lubrication is vital for car engines and it can be expensive when you get it wrong or when it’s not as effective as it could be. A Jan. 25, 2016 news item on Nanowerk highlights some research focused on improving the quality of engine lubrication,

When an automobile’s engine is improperly lubricated, it can be a major hit to the pocketbook and the environment.

For the average car, 15 percent of the fuel consumption is spent overcoming friction in the engine and transmission. When friction is high, gears have to work harder to move. This means the car burns more fuel and emits more carbon dioxide into the atmosphere.

“Every year, millions of tons of fuel are wasted because of friction,” said Northwestern Engineering’s Jiaxing Huang, associate professor of materials science and engineering. “It’s a serious problem.”

While oil helps reduce this friction, people have long searched for additives that enhance oil’s performance. Huang and his collaborators discovered that crumpled graphene balls are an extremely promising lubricant additive. In a series of tests, oil modified with crumpled graphene balls outperformed some commercial lubricants by 15 percent, both in terms of reducing friction and the degree of wear on steel surfaces.

A Jan. 25, 2015 McCormick School of Engineering at Northwestern University news release, which originated the news item, provides more information about the team’s work,

About five years ago, Huang discovered crumpled graphene balls — a novel type of ultrafine particles that resemble crumpled paper balls. The particles are made by drying tiny water droplets with graphene-based sheets inside. “Capillary force generated by the evaporation of water crumples the sheets into miniaturized paper balls,” Huang said. “Just like how we crumple a piece of paper with our hands.”

Shortly after making this discovery, Huang explained it to Chung [Yip-Wah Chung, professor of materials science and engineering] during a lunch in Hong Kong by crumpling a napkin and juggling it. “When the ball landed on the table, it rolled,” Chung recalled. “It reminded me of ball bearings that roll between surfaces to reduce friction.”

That “a-ha!” moment led to a collaboration among the two professors and Wang, who was in the middle of editing a new Encyclopedia of Tribology with Chung.

Nanoparticles, particularly carbon nanoparticles, previously have been studied to help increase the lubrication of oil. The particles, however, do not disperse well in oil and instead tend to clump together, which makes them less effective for lubrication. The particles may jam between the gear’s surfaces causing severe aggregation that increases friction and wear. To overcome this problem, past researchers have modified the particles with extra chemicals, called surfactants, to make them disperse. But this still doesn’t entirely solve the problem.

“Under friction, the surfactant molecules can rub off and decompose,” Chung said. “When that happens, the particles clump up again.”

Because of their unique shape, crumpled graphene balls self-disperse without needing surfactants that are attracted to oil. With their pointy surfaces, they are unable to make close contact with the other graphene balls. Even when they are squeezed together, they easily separate again when disturbed.

Huang and his team also found that performance of crumpled graphene balls is not sensitive to their concentrations in the oil. “A few are already sufficient, and if you increase the concentration by 10 times, performance is about the same,” Huang said. “For all other carbon additives, such performance is very sensitive to concentration. You have to find the sweet spot.”

“The problem with finding a sweet spot is that, during operation, the local concentration of particles near the surfaces under lubrication could fluctuate,” Wang [Q. Jane Wang, professor of mechanical engineering] added. “This leads to unstable performance for most other additive particles.”

Next, the team plans to explore the additional benefit of using crumpled graphene balls in oil: they can also be used as carriers. Because the ball-like particles have high surface area and open spaces, they are good carriers for materials with other functions, such as corrosion inhibition.

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

Self-dispersed crumpled graphene balls in oil for friction and wear reduction by Xuan Dou, Andrew R. Koltonow, Xingliang He, Hee Dong Jang, Qian Wang, Yip-Wah Chung, and Jiaxing Huang. PNAS 2016 doi:10 .1038/srep03863 Published ahead of print January 25, 2016

This paper is behind a paywall.

One final comment, it’s a bit unusual to see the term ‘carbon nanoparticle’. Generally speaking, carbon nanoparticles seem to have their own names, graphene, carbon nanotubes, and buckminsterfullerenes come to mind.

Speeding up bone growth with a tobacco virus

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Steven Powell in a June 22, 2012 article for the University of South Carolina news office describes progress that Qian Wang, a chemistry professor, and his colleagues at the University of South Carolina have made toward cutting down the time it takes to heal a bone. From the June 22, 2012 article (Note: I have removed a link),

Wang, Andrew Lee and co-workers just reported in Molecular Pharmaceutics that surfaces coated with bionanoparticles could greatly accelerate the early phases of bone growth. Their coatings, based in part on genetically modified Tobacco mosaic virus, reduced the amount of time it took to convert stem cells into bone nodules – from two weeks to just two days.

Here’s a description of the healing process,

The human body continuously generates and circulates cells that are undifferentiated; that is, they can be converted into the components of a range of tissues, such as skin or muscle or bone, depending on what the body needs.

The conversion of these cells – called stem cells – is set into motion by external cues. In bone healing, the body senses the break at the cellular level and begins converting stem cells into new bone cells at the location of the break, bonding the fracture back into a single unit.

There are reasons for wanting to speed the process,

The process is very slow, which is helpful in allowing a fracture to be properly set, but after that point the wait is at least an inconvenience, and in some cases highly detrimental.

“With a broken femur, a leg, you can be really incapacitated for a long time,” said Wang. “In cases like that, they sometimes inject a protein-based drug, BMP-2, which is very effective in speeding up the healing process. Unfortunately, it’s very expensive and can also have some side effects.”

Wang and his colleagues stumbled across a new approach to speeding up the healing process (Note: I have removed a link),

In a search for alternatives four years ago, Wang and colleagues uncovered some unexpected accelerants of bone growth: plant viruses. They originally meant for these viruses, which are harmless to humans, to work as controls. They coated glass surfaces with uniform coverings of the Turnip yellow mosaic virus and Tobacco mosaic virus, originally intending to use them as starting points for examining other potential variations.

But they were surprised to find that the coatings alone could reduce the amount of time to grow bone nodules from stem cells. Since then, Wang and co-workers have refined their approach to better define just what it is that accelerates bone growth.

This is a description of their latest refinements and what they imagine to be possible at some time in the future,

In the most recent effort spearheaded by Lee, they built up a layer-by-layer assembly underneath the virus coating to ensure stability. They also genetically modified the viral protein to enhance the interaction between the coating and the stem cells and help drive them toward bone growth.

Their efforts were rewarded with bone nodules that formed just two days after the addition of stem cells, compared to two weeks with a standard glass surface. They’re also carefully following the cellular signs involved with success. BMP-2 is involved, but as an intrinsic cellular product rather than an added drug.

“BMP-2 is bone morphogenetic protein 2. It can be added as a protein-based drug, but it’s a natural protein produced in the cell,” said Wang. “We see upregulation of the BMP-2 within 8 hours with the new scaffold.” They also find osteocalcin expression and calcium sequestration, two processes associated with bone formation, to be much more pronounced with their new coatings.

“What we’ve seen could prove very useful, particularly when it comes to external implants in bones,” said Wang. “With those, you have to add a foreign material, and knowing that a coating might increase the bone growth process is clearly beneficial.”

“But more importantly, we feel we’re making progress in a more general sense in bone engineering. We’re really showing the direct correlation between nanotopography and cellular response. If our results can be further developed, in the future you could use titanium to replace the bone, and you might be able to use different kinds of nanoscale patterning on the titanium surface to create all kinds of different cellular responses.” [emphasis mine]

I had not expected to leap from bone tissue engineering to creating titanium bones  the sort of thing that I imagine much interests the military.  As for “different cellular responses,” my imagination fails. What is being suggested? Thanks to the June 25,2012 news item on Nanowerk for alerting me to this work.