Tag Archives: Jie Liu

Next supercapacitor: crumpled graphene?

An Oct. 3, 2014 news item on ScienceDaily features the use of graphene as a possible supercapacitor,

When someone crumples a sheet of paper, that usually means it’s about to be thrown away. But researchers have now found that crumpling a piece of graphene “paper” — a material formed by bonding together layers of the two-dimensional form of carbon — can actually yield new properties that could be useful for creating extremely stretchable supercapacitors to store energy for flexible electronic devices.

The finding is reported in the journal Scientific Reports by MIT’s {Massachusetts Institute of Technology] Xuanhe Zhao, an assistant professor of mechanical engineering and civil and environmental engineering, and four other authors. The new, flexible superconductors should be easy and inexpensive to fabricate, the team says.

An Oct. 3, 2014 MIT news release by David Chandler (also on EurekAlert), which originated the news item, explains the technology at more length,

“Many people are exploring graphene paper: It’s a good candidate for making supercapacitors, because of its large surface area per mass,” Zhao says. Now, he says, the development of flexible electronic devices, such as wearable or implantable biomedical sensors or monitoring devices, will require flexible power-storage systems.

Like batteries, supercapacitors can store electrical energy, but they primarily do so electrostatically, rather than chemically — meaning they can deliver their energy faster than batteries can. Now Zhao and his team have demonstrated that by crumpling a sheet of graphene paper into a chaotic mass of folds, they can make a supercapacitor that can easily be bent, folded, or stretched to as much as 800 percent of its original size. The team has made a simple supercapacitor using this method as a proof of principle.

The material can be crumpled and flattened up to 1,000 times, the team has demonstrated, without a significant loss of performance. “The graphene paper is pretty robust,” Zhao says, “and we can achieve very large deformations over multiple cycles.” Graphene, a structure of pure carbon just one atom thick with its carbon atoms arranged in a hexagonal array, is one of the strongest materials known.

To make the crumpled graphene paper, a sheet of the material was placed in a mechanical device that first compressed it in one direction, creating a series of parallel folds or pleats, and then in the other direction, leading to a chaotic, rumpled surface. When stretched, the material’s folds simply smooth themselves out.

Forming a capacitor requires two conductive layers — in this case, two sheets of crumpled graphene paper — with an insulating layer in between, which in this demonstration was made from a hydrogel material. Like the crumpled graphene, the hydrogel is highly deformable and stretchable, so the three layers remain in contact even while being flexed and pulled.

Though this initial demonstration was specifically to make a supercapacitor, the same crumpling technique could be applied to other uses, Zhao says. For example, the crumpled graphene material might be used as one electrode in a flexible battery, or could be used to make a stretchable sensor for specific chemical or biological molecules.

Here is a link to and a citation for the paper,

Stretchable and High-Performance Supercapacitors with Crumpled Graphene Papers by Jianfeng Zang, Changyong Cao, Yaying Feng, Jie Liu, & Xuanhe Zhao. Scientific Reports 4, Article number: 6492 doi:10.1038/srep06492 Published 01 October 2014

This is an open access article.

ETA Oct. 8, 2014: Dexter Johnson of the Nanoclast blog on the IEEE (Institute of Electrical and Electronics Engineers) website has an Oct. 7, 2014 post where he comments about the ‘flexibility’ aspect of this work.

Duke University’s (North Carolina, US) Center for Environmental Implications of NanoTechnology (CEINT) wins $15M grant

A Nov. 13, 2013 news item on Azonano announces that the Center for Environmental Implications of Nanotechnology (CEINT) at Duke University has been awarded $15M,

A pioneering, multi-institution research center headquartered at Duke’s Pratt School of Engineering has just won $15-million grant renewal from the National Science Foundation and the US Environmental Protection Agency to continue learning more about where nanoparticles accumulate, how they interact with other chemicals and how they affect the environment.

Founded in 2008, the Center for Environmental Implications of NanoTechnology (CEINT) has been evaluating the effect of long-term nanomaterial exposure on organisms and ecosystems.

“The previous focus has been on studying simple, uniform nanomaterials in simple environments,” said Mark Wiesner, James L. Meriam Professor of Civil & Environmental Engineering and director of CEINT. “As we look to the next five years, we envision a dramatically different landscape. We will be evaluating more complex nanomaterials in more realistic natural environments such as agricultural lands and water treatment systems where these materials are likely to be found.”

The Nov. 11, 2013 Duke University news release by Karyn Hede, which originated the news item, provides some history and context for CEINT (Note: Links have been removed),

When CEINT formed, little research had been done on how materials manufactured at the nanoscale—about 1/10,000th the diameter of a human hair—enter the environment and whether their size and unique properties render them a new category of environmental risk. For example, nanoparticles can be highly reactive with other chemicals in the environment and had been shown to disrupt activities in living organisms. Indeed, nanosilver is used in clothing precisely because it effectively kills odor-causing bacteria.

To tackle this expansive research agenda, CEINT leadership assembled a multi-institutional research team encompassing expertise in ecosystems biology, chemistry, geology, materials science, computational science, mathematical modeling and other specialties, to complement its engineering expertise. The Center has 29 faculty collaborators, as well as 76 graduate and undergraduate students participating in research. Over its first five years, CEINT has answered some of the most pressing questions about environmental risk and has learned where to focus future research.

The center also pioneered the use of a new test chamber, called a mesocosm, that replicates a small wetland environment. “Over the long term, we want to evaluate how nanoparticles bioaccumulate in complex food webs,” said Emily Bernhardt, an associate professor of biology at Duke and ecosystem ecologist who helped design the simulated ecosystems. “The additional funding will allow us to study the subtle effect of low-dose exposure on ecosystems over time, as well as complex interactions among nanoparticles and other environmental contaminants.”

Looking forward, the investigators at CEINT plan to expand the use of systems modeling and to create a “knowledge commons,” a place to store various kinds of data that can then be analyzed as a whole, said CEINT Executive Director Christine Hendren.

“Our investigators and collaborators are located across the globe,” Hendren added. “We are committed to disseminating information that can be translated into responsible regulatory frameworks and that will be available to compare with results of future research.”

Key findings from CEINT’s first five years include:

Naturally occurring nanomaterials far outnumber engineered particles. CEINT scientist Michael Hochella, a geoscientist at Virginia Tech, inventoried nanoparticles and concluded that natural nanoparticles are found everywhere, from dust in the atmosphere to sea spray to volcanoes. The environmental risks of these natural nanomaterials are difficult to separate from engineered nanomaterials.

Engineered nanoparticles change once they enter the environment. Gregory V. Lowry, deputy director of CEINT and professor at Carnegie Mellon University, Pittsburgh, along with colleagues from the University of Birmingham, U.K. and the University of South Carolina found that the relatively large surface area of nanoparticles makes them highly reactive once they enter the environment. These transformations will alter their movement and toxicity and must be considered when studying nanomaterials. Their review article on this topic was named the best feature article of 2012 by the journal Environmental Science and Technology.

Nanoparticles can be visualized, even in complex environmental samples. A research team led by CEINT investigators Jie Liu, associate professor of chemistry at Duke, and CEINT Director Mark Wiesner showed that more than a dozen types of engineered nanoparticles, including silver, gold, and titanium dioxide, along with carbon nanotubes, can be surveyed using a technique called hyperspectral imaging, which measures light scattering caused by different types of nanoparticles. The new technique, co-developed by postdoctoral researcher Appala Raju Badireddy, is sensitive enough to analyze nanoparticles found in water samples ranging from ultrapurified to wastewater. It will be used in future long-term studies of how nanoparticles move and accumulate in ecological systems.

It is possible to estimate current and future volume of engineered nanomaterials. Understanding the volume of nanomaterials being produced and released into the environment is a crucial factor in risk assessment. CEINT researchers led by Christine Hendren measured the upper- and lower-bound annual U.S. production of five classes of nanomaterials, totaling as much as a combined 40,000 metric tons annually as of 2011.

Silver nanoparticles caused environmental stress in a simulated wetland environment. CEINT has developed  “mesocosms,”  open-air terrarium-like structures that simulate wetland ecosystems that can be evaluated over time. Even low doses of silver nanoparticles used in many consumer products produced about a third less biomass in a mesocosm. The researchers will now  look at how nanomaterials are transferred between organisms in a mesocosm.

I have written about CEINT and its work, including the mesocosm, many times. My August 15, 2011 posting offers an introduction to the CEINT mesocosm.

Using carbon nanotubes to treat neural injuries?

It’s more usual to hear about toxicology when discussing carbon nanotubes (CNTs) and health but recent work from Duke University Medical Center suggests that CNTs could be used in therapeutic treatments for neural injuries. From the Dec. 10,2012 news item on ScienceDaily,

A nanomaterial engineered by researchers at Duke can help regulate chloride levels in nerve cells that contribute to chronic pain, epilepsy, and traumatic brain injury.

The findings, published online Dec. 10, 2012, in the journal Small, were demonstrated in individual nerve cells as well as in the brains of mice and rats, and may have future applications in intracranial or spinal devices to help treat neural injuries.

The Dec. 10, 2012 news release from Duke Medicine News and Communications discusses carbon nanotubes and the applications they are usually associated with,

Carbon nanotubes are a nanomaterial with unique features, including mechanical strength and electrical conductivity. These characteristics, along with their tiny size, make them appealing to researchers in technology and medicine alike.

In a world of shrinking computers and smartphones, carbon nanotubes have been tapped as a solution for improving microchips. They outpace silicon microchips in size and performance, meeting a demand for smaller, faster devices. For people with nerve injury and certain neurological disorders, devices coated with or entirely made of carbon nanotubes could offer a new avenue for improving treatment options.

“Carbon nanotubes hold great promise for an array of applications, and we are only beginning to see their enormous potential,” said lead author Wolfgang Liedtke, M.D., PhD, associate professor of medicine and neurobiology at Duke. “Their exceptional mechanical and electrical properties make them ideal for developing devices that interface with nervous tissues. However, the precise mechanisms behind carbon nanotubes and their effect on neurons remain elusive.”

One of the Duke researchers actually developed a new kind of carbon nanotube for this research (from the Duke news release),

Not all carbon nanotubes are the same. Jie Liu, PhD, George Barth Geller Professor of Chemistry at Duke University and senior author of the study, developed specific carbon nanotubes that are extraordinarily pure. Termed few-walled carbon nanotubes, they have superior properties to their commercially-available counterparts.

Duke researchers initially set out to gauge if carbon nanotubes had toxic or adverse effects on living tissue. Studying neurons cultured from rodents, representing a “cerebral cortex in a dish,” they found the opposite. Exposing the cells to carbon nanotubes appeared to have a nourishing effect on the neurons, making them bigger and stronger.

“Previous studies have looked at the behavior of carbon nanotubes on neurons. However, the impurity in the nanotubes significantly affected the results. After we developed pure few-walled carbon nanotubes in our lab, we discovered that nanotubes actually accelerated the growth of the neuronal cells significantly,” said Liu.

Here’s what happens in some cases of neural injury and the impact that few-walled carbon nanotubes might have on future therapeutics (from the Duke news release),

Neural circuits can be corrupted by elevated chloride within neurons. A number of diseases involve such neural circuit damage, including chronic pain, epilepsy, and traumatic brain injury.

Low levels of chloride within neurons are maintained by a chloride transporter protein called KCC2, which functions by churning chloride ions out of the cell. In mature neurons, there is no back-up for this function.

The immature neurons cultured in Liedtke’s laboratory had high levels of chloride, but as the cells matured, their chloride levels dropped as KCC2 increased. When the neurons were exposed to carbon nanotubes, the cells matured much faster, and the chloride levels dropped more quickly. Researchers learned that younger cells exposed to carbon nanotubes produced more KCC2 protein.

“Carbon nanotubes enhanced the regulation of chloride in neurons to normal levels. These changes are of enormous significance to the cell,” Liedtke said.

The increase in KCC2 protein was also connected to a rise in calcium in the neurons. The increased calcium levels activated a protein found in the brain called CaMKII which signals a neuron to make more KCC2.

Similar results were observed in the brains of mice, as the carbon nanotubes prompted an increase in activity of the KCC2 gene, suggesting that the few-walled carbon nanotubes influence gene regulation of KCC2.

These findings may lead to the development of a new generation of neural engineering devices using carbon nanotubes. Existing devices that modulate the function of nerve cells use electrical systems that date back several decades.

“We hope that carbon nanotubes will work as well in injured nerves as they did in our study of developing neurons,” Liedtke continued. “The use of carbon nanotubes is just in its infancy, and we are excited to be part of a developing field with so much potential.”

Naturally (sarcasm alert), the researchers have done this (from the Duke news release),

Liedtke and Liu have filed a preliminary patent application for the few-walled carbon nanotubes used in this research. [emphasis mine]

How how many new therapies will be developed (or even researched) if the materials needed for the research are patented?

For anyone who’s interested in the paper, here’s a citation and link (from the ScienceDaily news item),

Wolfgang Liedtke, Michele Yeo, Hongbo Zhang, Yiding Wang, Michelle Gignac, Sara Miller, Ken Berglund and Jie Liu. Highly Conductive Carbon Nanotube Matrix Accelerates Developmental Chloride Extrusion in Central Nervous System Neurons by Increased Expression of Chloride Transporter KCC2. Small, 10 DEC 2012 DOI: 10.1002/smll.201201994

This paper is behind a paywall.

It should be mentioned that ScienceDaily offers a choice of citation formats, APA or MLA. This citation is in APA format.

Brain-controlled robotic arm means drinking coffee by yourself for the first time in 15 years

The video shows a woman getting herself a cup of coffee for the first time in 15 years. She’s tetraplegic (aka quadraplegic) and is participating in a research project funded by DARPA (US Defense Advanced Research Projects Agency) for developing neuroprostheses.

Kudos to the researchers and to the woman for her courage and persistence. The May 17, 2012 news item on Nanowerk provides some background,

DARPA launched the Revolutionizing Prosthetics program in 2006 to advance the state of upper-limb prosthetic technology with the goals of improving quality of life for service-disabled veterans and ultimately giving them the option of returning to duty. [emphasis mine] Since then, Revolutionizing Prosthetics teams have developed two anthropomorphic advanced modular prototype prosthetic arm systems, including sockets, which offer increased range of motion, dexterity and control options. Through DARPA-funded work and partnerships with external researchers, the arm systems and supporting technology continue to advance.

The newest development on this project (Revolutionizing Prosthetics) comes from the BrainGate team (mentioned in my April 19, 2012 posting [scroll down about 1/5th of the way) many of whom are affiliated with Brown University.  Alison Abbott’s May 16, 2012 Nature article provides some insight into the latest research,

The study participants — known as Cathy and Bob — had had strokes that damaged their brain stems and left them with tetraplegia and unable to speak. Neurosurgeons implanted tiny recording devices containing almost 100 hair-thin electrodes in the motor cortex of their brains, to record the neuronal signals associated with intention to move.

The work is part of the BrainGate2 clinical trial, led by John Donoghue, director of the Brown Institute for Brain Science in Providence. His team has previously reported a trial in which two participants were able to move a cursor on a computer screen with their thoughts.

The neuroscientists are working closely with computer scientists and robotics experts. The BrainGate2 trial uses two types of robotic arm: the DEKA Arm System, which is being developed for prosthetic limbs in collaboration with US military, and a heavier robot arm being developed by the German Aerospace Centre (DLR) as an external assistive device.

In the latest study, the two participants were given 30 seconds to reach and grasp foam balls. Using the DEKA arm, Bob — who had his stroke in 2006 and was given the neural implant five months before the study —- was able to grasp the targets 62% of the time. Cathy had a 46% success rate with the DEKA arm and a 21% success rate with the DLR arm. She successfully raised the bottled coffee to her lips in four out of six trials.

Nature has published the research paper (citation):

Reach and grasp by people with tetraplegia using a neurally controlled robotic arm

Authors: Leigh R. Hochberg, Daniel Bacher, Beata Jarosiewicz, Nicolas Y. Masse, John D. Simeral, Joern Vogel, Sami Haddadin, Jie Liu, Sydney S. Cash, Patrick van der Smagt and John P. Donoghue

Nature, 485, 372–375 (17 May 2012) doi:10.1038/nature11076

The paper is behind a paywall but if you have access, it’s here.

In the excess emotion after watching that video, I forgot for a moment that the ultimate is to repair soldiers and hopefully get them back into the field.