Move Over, Silicon, There’s a New Circuit in Town

Hybrid CNT/IGZO circuits fabricated on a polyimide film laminated on a polydimethylsiloxane (PDMS) substrate (USC Viterbi / Chongwu Zhou)

When it comes to electronics, silicon will now have to share the spotlight.

In a paper recently published in Nature Communications, researchers from the USC Viterbi School of Engineering describe how they have overcome a major issue in carbon nanotube technology by developing a flexible, energy-efficient hybrid circuit combining carbon nanotube thin film transistors with other thin film transistors. This hybrid could take the place of silicon as the traditional transistor material used in electronic chips, since carbon nanotubes are more transparent, flexible, and can be processed at a lower cost.

“The possibilities are endless, as digital circuits can be used in any electronics,” Chen said. “One day we’ll be able to print these circuits as easily as newspapers.”

Read more . . .

 

The Latest on: Hybrid thin film transistors

via  Bing News

 

 

Bioprinting a 3D Liver-Like Device to Detoxify the Blood

Nanoengineering Professor Shaochen Chen

Nanoengineers at the University of California, San Diego have developed a 3D-printed device inspired by the liver to remove dangerous toxins from the blood.

The device, which is designed to be used outside the body — much like dialysis – uses nanoparticles to trap pore-forming toxins that can damage cellular membranes and are a key factor in illnesses that result from animal bites and stings, and bacterial infections. Their findings were published May 8 in the journal Nature Communications.

Nanoparticles have already been shown to be effective at neutralizing pore-forming toxins in the blood, but if those nanoparticles cannot be effectively digested, they can accumulate in the liver creating a risk of secondary poisoning, especially among patients who are already at risk of liver failure. To solve this problem, a research team led by nanoengineering professor Shaochen Chen created a 3D-printed hydrogel matrix to house nanoparticles, forming a device that mimics the function of the liver by sensing, attracting and capturing toxins routed from the blood.  The device, which is in the proof-of-concept stage, mimics the structure of the liver but has a larger surface area designed to efficiently attract and trap toxins within the device. In an in vitro study, the device completely neutralized pore-forming toxins.

“One unique feature of this device is that it turns red when the toxins are captured,” said the co-first author, Xin Qu, who is a postdoctoral researcher working in Chen’s laboratory.  “The concept of using 3D printing to encapsulate functional nanoparticles in a biocompatible hydrogel is novel,” said Chen. “This will inspire many new designs for detoxification techniques since 3D printing allows user-specific or site-specific manufacturing of highly functional products,” Chen said.

Chen’s lab has already demonstrated the ability to print complex 3D microstructures, such as blood vessels, in mere seconds out of soft biocompatible hydrogels that contain living cells.

Chen’s biofabrication technology, called dynamic optical projection stereolithography (DOPsL), can produce the micro- and nanoscale resolution required to print tissues that mimic nature’s fine-grained details, including blood vessels, which are essential for distributing nutrients and oxygen throughout the body. The biofabrication technique uses a computer projection system and precisely controlled micromirrors to shine light on a selected area of a solution containing photo-sensitive biopolymers and cells. This photo-induced solidification process forms one layer of solid structure at a time, but in a continuous fashion.

Read more . . .

 

The Latest on: Biofabrication

via  Bing News

 

Using tobacco to thwart West Nile virus

ASU researchers Qiang “Shawn ” Chen and Huafang “Lily ” Lai infiltrate a tobacco plant to produce monoclonal antibodies against West Nile virus.

A new generation of potentially safer and more cost-effective therapeutics against West Nile virus, and other pathogens

An international research group led by Arizona State University professor Qiang “Shawn” Chen has developed a new generation of potentially safer and more cost-effective therapeutics against West Nile virus, and other pathogens.

The therapeutics, known as monoclonal antibodies (MAbs) and their derivatives, were shown to neutralize and protect mice against a lethal dose challenge of West Nile virus—even as late as 4 days after the initial infection.

“The overarching goal of our research is to create an innovative, yet sustainable and accessible, low cost solution to combat the global threat of West Nile virus,” said Chen, a researcher at Arizona State University’s Biodesign Institute and professor in the Department of TEIM.

West Nile virus is spread by infected mosquitoes, and targets the central nervous system. It can be a serious, life-altering and even fatal disease and currently, there is no cure or drug treatment against West Nile virus, which has been widely spread across the U.S., Canada, Latin America and the Caribbean.

“The goal of this latest research was twofold,” said Chen. “First, we wanted to show proof-of-concept, demonstrating that tobacco plants can be used to manufacture large and complex MAb-based therapeutics. Secondly, we’ve wanted to improve the delivery of the therapeutic into the brain to combat West Nile virus at the place where it does the greatest harm.”

The study appears in the March 27 online edition of PLOS ONE. Along with Chen, the research team included Junyun He, Huafang “Lily” Lai, Michael Engle, Sergey Gorlatov, Clemens Gruber, Herta Steinkellner and long-time Washington University collaborator Michael S. Diamond.

Chen’s group has been a pioneer in producing MAbs as therapeutic candidates in plants, including tobacco and lettuce plants. A couple of years ago, his team demonstrated that their first candidate, pHu-E16, could neutralize West Nile infection and protect mice from exposure. MAbs target proteins found on the surface of West Nile virus.

However, this antibody was not able to accumulate at high levels in the brain.

One approach to tackle this challenge is to program into the therapeutic antibodies the capability of binding to receptors that can help the MAbs to cross into the brain. Chen wanted to use this strategy to produce a more effective way to combat West Nile virus.

In the new study, they improved upon their pHu-E16 design, making half a dozen new variants that could, for the first time, lead to the development of MAbs that effectively target the brain and neutralize West Nile virus.

Mice were infected with a lethal dose of West Nile virus, and increasing amounts of a MAb therapeutic were delivered as a single dose the same day of infection. In another experiment, Chen’s team tested whether the therapeutic, called Tetra pHu-E16, could be effective after infection. In this case, the therapeutic was administered 4 days after West Nile virus infection, when the virus has already spread to the brain. In each case, they protected up to 90 percent of the mice from lethal infection.

This is the first instance of such an effect and makes possible neutralizing West Nile virus even after infection by a tetravalent MAb. The tetravalent MAbs design will offer the researchers greater flexibility toward selection of disease, tissue and antigen targets.

For Chen, this also gives promise to his team developing a plant-based system to dramatically reduce the costs of commercial manufacturing of MAbs.

“This study is a major step forward for plant-based MAbs, and also demonstrates for the first time the capacity of plants to express and assemble large, complex and functional tetravalent MAb complexes,” said Chen.

MAbs are a hot and highly competitive research field, having been shown to effectively target cancer, autoimmune and inflammatory diseases. Now a $60 billion market for the biotechnology and pharmaceutical sectors, growth of the market has been hampered by high development costs of producing these in animal cell systems, which when factoring in a long period for manufacturing, R&D and clinical trials, may reach around $1 billion per each therapeutic candidate.

Therapeutic MAbs are typically made in animal host cells and assembled into Y-shaped complexes. Until now, tetravalent MAbs had never been made in a plant system before. To make the potential therapeutics, the group is able to use young tobacco plants and a protein expression system to make and harvest the proteins in the leaves.

For the study, MAbs were rapidly produced in tobacco plants in as little as ten days, giving promise to change the image of scourged product that causes lung cancer into a manufacturing system for societal benefits against infectious diseases.

“It is our hope that these results may usher in new age of cost-effective, MAbs therapeutics against WNV and other neurological diseases,” said Chen. “Our next step is to move this forward with the development of bifunctional MAbs that can target to the brain with the ultimate goal of entering human clinical trials.”

Read more . . .

 

The Latest on: West Nile virus

via  Bing News

 

Research could bring new devices that control heat flow

ruan-rectificationLO

Researchers are proposing a new technology that controls the flow of heat the way electronic devices control electrical current. Triangular graphene nanoribbons (a) are proposed as a new thermal rectifier, in which the heat flow in one direction is larger than that in the opposite direction. Thermal rectification (b) is not limited to graphene, but can also be seen in other “asymmetric nanostructure materials” including thin films, pyramidal quantum dots, nanocones and triangles. (Purdue University image)

Researchers are proposing a new technology that might control the flow of heat the way electronic devices control electrical current, an advance that could have applications in a diverse range of fields from electronics to textiles.

The concept uses tiny triangular structures to control “phonons,” quantum-mechanical phenomena that describe how vibrations travel through a material’s crystal structure.

Findings in research using advanced simulations show the triangular or T-shaped structures – if small enough in width – are capable of “thermal rectification,” or permitting a greater flow of heat in one direction than in the opposite direction, said Xiulin Ruan, an associate professor in Purdue University‘s School of Mechanical Engineering and Birck Nanotechnology Center.

Rectification has made possible transistors, diodes and memory circuits central to the semiconductor industry. The new devices are thermal rectifiers that might perform the same function, but with phonons instead of electrical current.

“In most systems, heat flow is equal in both directions, so there are no thermal devices like electrical diodes. However, if we are able to control heat flow like we control electricity using diodes then we can enable a lot of new and exciting thermal devices including thermal switches, thermal transistors, logic gates and memory,” said Ruan, whose research group collaborated with a group led by Yong Chen, an associate professor in Purdue’s Department of Physics and School of Electrical and Computer Engineering. “People are just starting to understand how it works, and it is quite far from being used in applications.”

Findings are detailed in a research paper that has appeared online in the journal Nano Letters and will be published in an upcoming issue of the journal. The paper was authored by doctoral students Yan Wang, Ajit Vallabhaneni and Jiuning Hu and former doctoral student Bo Qiu; Chen; and Ruan.

The researchers used an advanced simulation method called molecular dynamics to demonstrate thermal rectification in structures called “asymmetric graphene nanoribbons.” Molecular dynamics simulations can simulate the vibrations of atoms and predict the heat flow in a material.

Graphene, an extremely thin layer of carbon, is promising for applications in electronics and computers. The triangular structure must be tiny in width to make possible the “lateral confinement” of phonons needed for the effect. Findings also show thermal rectification is not limited to graphene but could be seen in other materials in structures such as pyramidal, trapezoidal or T-shaped designs.

Hu, Ruan, and Chen also published a paper four years ago in the journal Nano Letters, among the first to propose asymmetric graphene nanoribbons as a thermal rectifier in research using the molecular dynamics simulations. Although numerous studies have been devoted to this topic since then, until now researchers did not know the mechanism behind thermal rectification. The new findings show that this mechanism works by restricting vibrations as they travel through the small lateral direction of an asymmetrical structure.

“We demonstrate that other asymmetric materials, such as asymmetric nanowires, thin ?lms, and quantum dots of a single material can also be high-performance thermal recti?ers, as long as you have lateral confinement,” Ruan said. “This really broadens the potential of this rectification to a much wider spectrum of applications.”

Thermal rectification is not seen in larger triangular-shape structures because they lack lateral confinement. In order for lateral confinement to be produced, the cross section of the structure must be much smaller than the “mean free path” of a phonon, or only a few to hundreds of nanometers depending on the material, Wang said.

“This is the average distance a phonon can travel before it collides with another phonon,” he said.

However, although the devices must be tiny, they could be linked in series to produce larger structures and better rectification performance.

The concept could find uses in “thermal management” applications for computers and electronics, buildings and even clothing.

“For example, on a winter night you don’t want a building to lose heat quickly to the outside, while during the day you want the building to be warmed up by the sun, so it would be good to have building materials that permit the flow of heat in one direction, but not the other,” Ruan said.

A potential, although speculative, future application could be thermal transistors. Unlike conventional transistors, thermal transistors would not require the use of silicon, are based on phonons rather than electrons and might make use of the large amount of waste heat that is already generated in most practical electronics, said Chen.

Read more . . .

 

The Latest on: Thermal management

via Google News

 

The Latest on: Thermal management

via  Bing News

 

Neuron regeneration may help sufferers of brain injury, Alzheimer’s disease

Chen_InvivoConversion_12-2013_0

Scientists have used supporting cells of the central nervous system, glial cells, to regenerate from damaged cells the healthy and functional neurons that are critical for transmitting signals in the brain, shown in green in this image in the brain of a mouse with Alzheimer’s disease. The red areas are the red-stained nuclei of neuron cells.

Researchers at Penn State have developed an innovative technology to regenerate functional neurons after brain injury and also in model systems used for research on Alzheimer’s disease.

The scientists have used supporting cells of the central nervous system, glial cells, to regenerate healthy, functional neurons, which are critical for transmitting signals in the brain.

Gong Chen, a professor of biology, the Verne M. Willaman Chair in Life Sciences at Penn State, and the leader of the research team, called the method a breakthrough in the long journey toward brain repair.

“This technology may be developed into a new therapeutic treatment for traumatic brain and spinal cord injuries, stroke, Alzheimer’s disease, Parkinson’s disease and other neurological disorders,” Chen said. The research was posted online Dec. 19 by the journal Cell Stem Cell.

When the brain is harmed by injury or disease, neurons often die or degenerate, but glial cells become more branched and numerous. These “reactive glial cells” initially build a defense system to prevent bacteria and toxins from invading healthy tissues, but this process eventually forms glial scars that limit the growth of healthy neurons.

“A brain-injury site is like a car-crash site,” Chen explained. “Reactive glial cells are like police vehicles, ambulances and fire trucks immediately rushing in to help — but these rescue vehicles can cause problems if too many of them get stuck at the scene. The problem with reactive glial cells is that they often stay at the injury site, forming a glial scar and preventing neurons from growing back into the injured areas.”

So several years ago, Chen’s lab tested new ways to transform glial scar tissue back to normal neural tissue.

“There are more reactive glial cells and fewer functional neurons in the injury site,” Chen said, “so we hypothesized that we might be able to convert glial cells in the scar into functional neurons at the site of injury in the brain. This research was inspired by the Nobel Prize-winning technology of induced pluripotent stem cells (iPSCs) developed in Shinya Yamanaka’s group, which showed how to reprogram skin cells into stem cells.”

Chen and his team began by studying how reactive glial cells respond to a specific protein, NeuroD1, which is known to be important in the formation of nerve cells in the hippocampus area of adult brains. They hypothesized that expressing NeuroD1 protein into the reactive glial cells at the injury site might help to generate new neurons — just as it does in the hippocampus. To test this hypothesis, his team infected reactive glial cells with a retrovirus that specifies the genetic code for the NeuroD1 protein.

“The retrovirus we used is replication-deficient and thus cannot kill infected cells like other viruses found in the wild,” Chen said. “More importantly, a retrovirus can infect only dividing cells such as reactive glial cells, but it does not affect neurons, which makes it ideal for therapeutic use with minimal side effect on normal brain functions.”

In a first test, Chen and his team investigated whether reactive glial cells can be converted into functional neurons after injecting NeuroD1 retrovirus into the cortex area of adult mice. The scientists found that two types of reactive glial cells — star-shaped astroglial cells and NG2 glial cells — were reprogrammed into neurons within one week after being infected with the NeuroD1 retrovirus.

“Interestingly, the reactive astroglial cells were reprogrammed into excitatory neurons, whereas the NG2 cells were reprogrammed into both excitatory and inhibitory neurons, making it possible to achieve an excitation-inhibition balance in the brain after reprogramming,” Chen said.

His lab also performed electrophysiological tests, which demonstrated that the new neurons converted by the NeuroD1 retrovirus could receive neurotransmitter signals from other nerve cells, suggesting that the newly converted neurons had successfully integrated into local neural circuits.

In a second test, Chen and his team used a transgenic-mouse model for Alzheimer’s disease, and demonstrated that reactive glial cells in the mouse’s diseased brain also can be converted into functional neurons. Furthermore, the team demonstrated that even in 14-month-old mice with Alzheimer’s disease — an age roughly equivalent to 60 years old for humans — injection of the NeuroD1 retrovirus into a mouse cortex can still induce a large number of newborn neurons reprogrammed from reactive glial cells.

“Therefore, the conversion technology that we have demonstrated in the brains of mice potentially may be used to regenerate functional neurons in people with Alzheimer’s disease,” Chen said.

Read more . . .

 

The Latest on: Neuron regeneration

via  Bing News