Electronics: Printing of flexible, stretchable silver nanowire circuits

Researchers at North Carolina State University ( NC State) have developed a new technique that allows them to print circuits on flexible, stretchable substrates using silver nanowires. The advance makes it possible to integrate the material into a wide array of electronic devices.

Silver nanowires have drawn significant interest in recent years for use in many applications, ranging from prosthetic devices to wearable health sensors, due to their flexibility, stretchability and conductive properties. While proof-of-concept experiments have been promising, there have been significant challenges to printing highly integrated circuits using silver nanowires. Silver nanoparticles can be used to print circuits, but the nanoparticles produce circuits that are more brittle and less conductive than silver nanowires. But conventional techniques for printing circuits don’t work well with silver nanowires; the nanowires often clog the printing nozzles.

Our approach uses electrohydrodynamic printing, which relies on electrostatic force to eject the ink from the nozzle and draw it to the appropriate site on the substrate,” says Jingyan Dong, co-corresponding author of a paper on the work and an associate professor in NC State’s Edward P. Fitts Department of Industrial & Systems Engineering. “This approach allows us to use a very wide nozzle – which prevents clogging – while retaining very fine printing resolution.” “And because our ‘ink’ consists of a solvent containing silver nanowires that are typically more than 20 micrometers long, the resulting circuits have the desired conductivity, flexibility and stretchability,” says Yong Zhu, a professor of mechanical engineering at NC State and co-corresponding author of the paper.

In addition, the solvent we use is both nontoxic and water-soluble,” says Zheng Cui, a Ph.D. student at NC State and lead author of the paper. “Once the circuit is printed, the solvent can simply be washed off.” What’s more, the size of the printing area is limited only by the size of the printer, meaning the technique could be easily scaled up.

The researchers have used the new technique to create prototypes that make use of the silver nanowire circuits, including a glove with an internal heater and a wearable electrode for use in electrocardiography. NC State has filed a provisional patent on the technique.

Source: https://news.ncsu.edu/

How To Convert 90% Of Water Into Hydrogen

Researchers from North Carolina State University (NC State) have significantly boosted the efficiency of two techniques, for splitting water to create hydrogen gas and splitting carbon dioxide (CO2) to create carbon monoxide (CO). The products are valuable feedstock for clean energy and chemical manufacturing applications. The water-splitting process successfully converts 90 percent of water into hydrogen gas, while the CO2-splitting process converts more than 98 percent of the CO2 into CO. In addition, the process also uses the resulting oxygen to convert methane into syngas, which is itself a feedstock used to make fuels and other products.

These advances are made possible by materials that we specifically designed to have the desired thermodynamic properties for each process,” says Fanxing Li, an associate professor of chemical and biomolecular engineering at NC State who is corresponding author of two papers on the work. “These properties had not been reported before unless you used rare earth materials.”

For the CO2-splitting process, researchers developed a nanocomposite of strontium ferrite dispersed in a chemically inert matrix of calcium oxide or manganese oxide. As CO2 is run over a packed bed of particles composed of the nanocomposite, the nanocomposite material splits the CO2 and captures one of the oxygen atoms. This reduces the CO2, leaving only CO behind.

Previous CO2 conversion techniques have not been very efficient, converting well below 90 percent of the CO2 into CO,” Li says. “We reached conversion rates as high as 99 percent. “And CO is valuable because it can be used to make a variety of chemical products, including everything from polymers to acetic acid,” Li adds.

Meanwhile, the oxygen captured during the CO2-splitting process is combined with methane and converted into syngas using solar energy.

Source: https://news.ncsu.edu/

Nano Printing Heralds NanoComputers Era

A new technique using liquid metals to create integrated circuits that are just atoms thick could lead to the next big advance for electronics. The process opens the way for the production of large wafers around 1.5 nanometres in depth (a sheet of paper, by comparison, is 100,000nm thick). Other techniques have proven unreliable in terms of quality, difficult to scale up and function only at very high temperatures – 550 degrees or more.

Professor Kourosh Kalantar-zadeh, from RMIT’s School of Engineering in Australia , led the project with  colleagues from RMIT and researchers from CSIRO, Monash University, North Carolina State University and the the University of California, He observed that the electronics industry had “hit a barrier.

nano printing

The fundamental technology of car engines has not progressed since 1920 and now the same is happening to electronics. Mobile phones and computers are no more powerful than five years ago. That is why this new 2D printing technique is so important – creating many layers of incredibly thin electronic chips on the same surface dramatically increases processing power and reduces costsIt will allow for the next revolution in electronics.

Benjamin Carey, a researcher with RMIT and the CSIRO, said creating electronic wafers just atoms thick could overcome the limitations of current chip production. It could also produce materials that were extremely bendable, paving the way for flexible electronics. “However, none of the current technologies are able to create homogenous surfaces of atomically thin semiconductors on large surface areas that are useful for the industrial scale fabrication of chips.  Our solution is to use the metals gallium and indium, which have a low melting point.  These metals produce an atomically thin layer of oxide on their surface that naturally protects them. It is this thin oxide which we use in our fabrication method,”  explains Carey.

By rolling the liquid metal, the oxide layer can be transferred on to an electronic wafer, which is then sulphurised. The surface of the wafer can be pre-treated to form individual transistors.  We have used this novel method to create transistors and photo-detectors of very high gain and very high fabrication reliability in large scale,” he adds.

The paper outlining the new technique has been published in the journal Nature Communications.

Source: http://www.rmit.edu.au/

Nano-Terminators Target Cancer

Researchers at North Carolina State University (NC State) and the University of North Carolina at Chapel Hill  (NC-CH) have developed a new drug delivery technique that uses a biodegradable liquid metal to target cancer cells. The liquid metal drug delivery method promises to boost the effect of cancer drugs. To date, the technique has only been tested in an animal model.

Liquid-Metal nanoterminator

The advance here is that we have a drug-delivery technique that may enhance the effectiveness of the drugs being delivered, can help doctors locate tumors, can be produced in bulk, and appears to be wholly biodegradable with very low toxicity,” says Zhen Gu, corresponding author of a Nature Communications paper on the work and an assistant professor in the joint biomedical engineering program at NC State and UNC-CH. “And one of the advantages of this technique is that these liquid metal drug carriers – or ‘nano-terminators’ – are very easy to make.”

To create the nano-terminators, researchers place the bulk liquid metal (gallium indium alloy) into a solution that contains two types of molecules called polymeric ligands. The solution is then hit with ultrasound, which forces the liquid metal to burst into nanoscale droplets approximately 100 nanometers in diameter. The ligands in the solution attach to the surface of the droplets as they break away from the bulk liquid metal. Meanwhile, an oxidized “skin” forms on the surface of the nanodroplets. The oxidized skin, together with the ligands, prevents the nanodroplets from fusing back together.

The anticancer drug doxorubicin (Dox) is then introduced into the solution. One of the ligands on the nanodroplet sucks up the Dox and holds on to it. These drug-laden nanodroplets can then be separated from the solution and introduced into the bloodstream. The second type of ligand on the nanodroplets effectively seeks out cancer cells, causing receptors on the surface of the cancer cell to latch on to the nanodroplets. The cancer cell then absorbs the nanodroplets.

.Once absorbed, the higher level of acidity inside the cancer cell dissolves the oxidized skin of the nanodroplets. This releases the ligands, which will go on to release the Dox inside the cell. “Without the oxidized skin and ligands, the nanodroplets fuse together, forming larger drops of liquid metal,” says Michael Dickey, a co-author on this paper and professor in the Department of Chemical and Biomolecular Engineering at NC State. “These larger droplets are fairly easy to detect using diagnostic techniques, which can potentially help doctors locate tumors.”

Source: https://news.ncsu.edu/

Biodegradable Nanoparticles For Harmless Pesticides

In this lab at North Carolina State University the future of keeping crops free of harmful bacteria is taking shape – albeit a very small shape. Researcher Alexander Richter is designing a new type of nanoparticle with lignin, an organic polymer found in almost all plants and trees, at its core. Currently, silver based nanoparticles are used in a wide range of pesticides to treat crops, but while silver has strong anti-microbial properties, its use is controversial.


Their post-application activity when released into the environment was actually seen as a potential concern by the U.S. Environmental Protection Agency. This is because the particles may stay active after the application, they may translocate after the application, they may kill good bacteria in the environment, which is undesired” says Alexander Tichter.

Dr. Orlin Velev, Professor of  chemical and biomolecular engineering adds: “So the problem is how do you potentially remove that danger from engineered nanomaterials?” The answer was to use less silver and replace the metallic core with lignin, making the newly engineered particles biodegradable but still an effective weapon in tackling dangerous bacteria like e-coli.
Our idea, or our approach, was to see if we can, if this is the problem, we replace the metallic core, which doesn’t participate in microbial action, with a biodegradable core. And by doing so, we could actually make the nanoparticles keep their functionality but make them degradable while also reducing the amount of the silver core in the nanoparticle system“, explains Richter.  And that equates to safer fruits and vegetables that are treated with less with chemicals as they grow.
“We believe that this can lead to a new generation of agricultural treatment products, that they’re going to be more efficient, that they’re going to use less chemicals, and that they’re going to be more friendly toward the environment” says Dr. Yelev.
The team has started a company to take their research to the next level with the hopes of perfecting the technology, scaling it up, and preparing it for commercialization.

Source:  http://www.reuters.com/

Inhalable Vaccines For Influenza, Pneumonia

Researchers at the University of North Carolina at Chapel Hill and North Carolina State University have uncovered a novel approach to creating inhalable vaccines using nanoparticles that shows promise for targeting lung-specific diseases, such as influenza, pneumonia and tuberculosis.

The work, led by Cathy Fromen and Gregory Robbins, members of the DeSimone and Ting labs, reveals that a particle’s surface charge plays a key role in eliciting immune responses in the lung. Using the Particle Replication in Nonwetting Templates (PRINT) technology invented in the DeSimone lab, Fromen and Robbins were able to specifically modify the surface charge of protein-loaded particles while avoiding disruption of other particle features, demonstrating PRINT’s unique ability to modify particle attributes independently from one another.
When delivered through the lung, particles with a positive surface charge were shown to induce antibody responses both locally in the lung and systemically in the body. In contrast, negatively charged particles of the same composition led to weaker, and in some cases undetectable, immune responses, suggesting that particle charge is an important consideration for pulmonary vaccination.
The findings, published in the Proceedings of the National Academy of Sciences, also have broad public health implications for improving the accessibility of vaccines. An inhalable vaccine may eliminate the need for refrigeration, which can not only improve shelf life, but also enable distribution of vaccines to low-resource areas, including many developing countries where there is significant need for better access to vaccines.

Source: http://uncnews.unc.edu/

Nanoflowers Deliver Drugs To Cancer Cells

Biomedical engineering researchers have developed daisy-shaped, nanoscale structures that are made predominantly of anti-cancer drugs and are capable of introducing a “cocktail” of multiple drugs into cancer cells. The researchers are all part the joint biomedical engineering program at North Carolina State University and the University of North Carolina at Chapel Hill.
To make the “nanodaisies,” the researchers begin with a solution that contains a polymer called polyethylene glycol (PEG). The PEG forms long strands that have much shorter strands branching off to either side. Researchers directly link the anti-cancer drug camptothecin (CPT) onto the shorter strands and introduce the anti-cancer drug doxorubicin (Dox) into the solution. Once injected, the nanodaisies float through the bloodstream until they are absorbed by cancer cells. Once in a cancer cell, the drugs are released.

Early tests of the “nanodaisy” drug delivery technique show promise against a number of cancers
We found that this technique was much better than conventional drug-delivery techniques at inhibiting the growth of lung cancer tumors in mice,” says Dr. Zhen Gu, senior author of the paper. “And based on in vitro tests in nine different cell lines, the technique is also promising for use against leukemia, breast, prostate, liver, ovarian and brain cancers.”
Source: http://news.ncsu.edu/

Cancer-Killing Time Bomb

Biomedical engineering researchers have developed an anti-cancer drug delivery method that essentially smuggles the drug into a cancer cell before triggering its release. The method can be likened to keeping a cancer-killing bomb and its detonator separate until they are inside a cancer cell, where they then combine to destroy the cell.

This is an efficient, fast-acting way of delivering drugs to cancer cells and triggering cell death,” says Dr. Ran Mo, lead author of a paper on the work and a postdoctoral researcher in the joint biomedical engineering program at North Carolina State University and the University of North Carolina at Chapel Hill. “We also used lipid-based nanocapsules that are already in use for clinical applications, making it closer to use in the real world.”

The technique uses nanoscale lipid-based capsules, or liposomes, to deliver both the drug and the release mechanism into cancer cells. One set of liposomes contains adenosine-5’-triphosphate (ATP), the so-called “energy molecule.” A second set of liposomes contains an anti-cancer drug called doxorubicin (Dox) that is embedded in a complex of DNA molecules. When the DNA molecules come into contact with high levels of ATP, they unfold and release the Dox.

Source: http://news.ncsu.edu/

How To Increase Solar Cells Efficiency by 30%

Researchers from North Carolina State University and the Chinese Academy of Sciences have found an easy way to modify the molecular structure of a polymer commonly used in solar cells. Their modification can increase solar cell efficiency by more than 30 percent.

Polymer-based solar cells have two domains, consisting of an electron acceptor and an electron donor material. Excitons are the energy particles created by solar cells when light is absorbed. In order to be harnessed effectively as an energy source, excitons must be able to travel quickly to the interface of the donor and acceptor domains and retain as much of the light’s energy as possible.

solar cell in one molecule
The possible drawback in changing the molecular structure of these materials is that you may enhance one aspect of the solar cell but inadvertently create unintended consequences in devices that defeat the initial intent,” according to NC State physicist and co-author Harald Ade. “In this case, we have found a chemically easy way to change the electronic structure and enhance device efficiency by capturing a lager fraction of the light’s energy, without changing the material’s ability to absorb, create and transport energy.

The researchers’ findings appear in Advanced Materials.

Source http://news.ncsu.edu/

Nanoparticles Carry 2 Different Cancer-killing Drugs

Researchers have developed a technique for creating nanoparticles that carry two different cancer-killing drugs into the body and deliver those drugs to separate parts of the cancer cell where they will be most effective. The technique was developed by researchers at North Carolina State University and the University of North Carolina at Chapel Hill.
In testing on laboratory mice, our technique resulted in significant improvement in breast cancer tumor reduction as compared to conventional treatment techniques,” says Dr. Zhen Gu, senior author of a paper on the research and an assistant professor in the joint biomedical engineering program at NC State and UNC-Chapel Hill.
We designed this drug delivery vehicle using a ‘programmed’ strategy,” says Tianyue Jiang, a lead author in Dr. Gu’s lab. “Different drugs can be released at the right time in their right places,” adds Dr. Ran Mo, a postdoctoral researcher in Gu’s lab and the other lead author.
Source: http://news.ncsu.edu/

Diabetics: Ultrasound To Avoid the Needle

A new nanotechnology-based technique for regulating blood sugar in diabetics may give patients the ability to release insulin painlessly using a small ultrasound device, allowing them to go days between injections – rather than using needles to give themselves multiple insulin injections each day. The technique was developed by researchers at North Carolina State University and the University of North Carolina at Chapel Hill.
Ultrasound to cure diabetics

New technique allows diabetics to control insulin release with an injectable nano-network and portable ultrasound device

This is hopefully a big step toward giving diabetics a more painless method of maintaining healthy blood sugar levels,” says Dr. Zhen Gu, senior author of a paper on the research and an assistant professor in the joint biomedical engineering program at NC State and UNC-Chapel Hill.
Source: http://news.ncsu.edu/

Public Ready To Pay For Infos When Nanotech is Used in Food

New research from North Carolina State University (NC State) and the University of Minnesota finds that people in the United States want labels on food products that use nanotechnology – whether the nanotechnology is in the food or is used in food packaging. The research also shows that many people are willing to pay more for the labeling. Study participants were particularly supportive of labeling for products in which nanotechnology had been added to the food itself, though they were also in favor of labeling products in which nanotechnology had only been incorporated into the food packaging.
Hamburger made from a stem cell

We wanted to know whether people want nanotechnology in food to be labeled, and the vast majority of the participants in our study do,” says Dr. Jennifer Kuzma, senior author of a paper on the research and Professor of Public Administration at NC State. “Our study is the first research in the U.S. to take an in-depth, focus group approach to understanding the public perception of nanotechnology in foods.”

The researchers convened six focus groups – three in Minnesota and three in North Carolina – and gave study participants some basic information about nanotechnology and its use in food products. Participants were then asked a series of questions addressing whether food nanotechnology should be labeled.

Source: http://news.ncsu.edu/