Tag Archives: nanotubes

New plasma printing technique can deposit nanomaterials on flexible, 3D substrates

A new nanomaterial printing method could make it both easier and cheaper to create devices such as wearable chemical and biological sensors, data storage and integrated circuits — even on flexible surfaces such as paper or cloth. The secret? Plasma.

The nozzle firing a jet of carbon nanotubes with helium plasma off and on. When the plasma is off, the density of carbon nanotubes is small. The plasma focuses the nanotubes onto the substrate with high density and good adhesion.
Image credits NASA Ames Research Center.

Printing layers of nanoparticles of nanotubes onto a substrate doesn’t necessarily require any fancy hardware — in fact, the most common method today is to use an inkjet printer very similar to the one you might have in your home or office. Although these printers are cost efficient and have stood the test of time, they’re not without limitations. They can only print on rigid materials with liquid ink — and not all materials can be easily made into a liquid. But probably the most serious limitation is that they can only print on 2D objects.

Aerosol printing techniques solve some of these problems. They can be employed to deposit smooth, thin films of nanomaterials on flexible substrates. But because the “ink” has to be heated to several hundreds of degrees to dry, using flammable materials such as paper or cloth remains a big no-no.

A new printing method developed by researchers from NASA Ames and SLAC National Accelerator Laboratory works around this issue. The plasma-based printing system doesn’t a heat-treating phase — in fact, the whole takes place at temperatures around 40 degrees Celsius. It also doesn’t require the printing material to be liquid.

“You can use it to deposit things on paper, plastic, cotton, or any kind of textile,” said Mayya Meyyappan of NASA’s Ames Research Center.

“It’s ideal for soft substrates.”

The team demonstrated their technique by covering a sheet of paper in a layer of carbon nanotubes. To do this, they blasted a mixture of carbon nanotubes and helium-ion plasma through a nozzle directly onto the paper. Because the plasma focuses the particles onto the paper’s surface, they form a well consolidated layer without requiring further heat-treatment.

They then printed two simple chemical and biological sensors. By adding certain molecules to the nanotube-plasma cocktail, they can change the tubes’ electrical resistance and response to certain compounds. The chemical sensor was designed to detect ammonia gas and the biological one was tailored to respond to dopamine, a neurotransmitter linked to disorders like Parkinson’s and epilepsy.

But these are just simple proof-of-concept constructs, Meyyappan said.

“There’s a wide range of biosensing applications,” she added.

Applications like monitoring cholesterol levels, checking for pathogens or hormonal imbalances, to name a few.

This method is very versatile and can easily be scaled up — just add more nozzles. For example, a shower-head type system could print large surfaces at once. Alternatively, it could be designed to act like a hose, spraying nanomaterials on 3D surfaces.

“It can do things inkjet printing cannot do,” Meyyappan said. “But [it can do] anything inkjet printing can do, it can be pretty competitive.”

Meyyappan said that the method is ready for commercial applications, and should be relatively simple and inexpensive to develop. The team is now tweaking their technique to allow for other printing materials, such as copper. This would allow them to print materials used for batteries onto thin sheets of metal such as aluminum. The sheet can then be rolled up to make very tiny, very powerful batteries for cellphones or other devices.

The full paper, titled “Plasma jet printing for flexible substrate” has been published online in the journal Applied Physics Letters and can be read here.

Pulsed near infrared light (shown in red) is shone onto a tumor (shown in white) that is encased in blood vessels. The tumor is imaged by multispectral optoacoustic tomography via the ultrasound emission (shown in blue) from the gold nanotubes. (credit: Jing Claussen/iThera Medical, Germany)

Three ways gold nanotubes are helping beat cancer

British researchers have demonstrated three ways gold nanotubes can be used against cancer: 1) high resolution in-vivo imaging; 2) drug delivery vehicles; 3) agents that destroy cancer itself. Their work shouldn’t be viewed as yet “another” hack that seeks to eradicate cancer. We need to be more realistic than this. Instead, the findings have the potential to be a great measure that both diagnoses and treats cancer at the same time, complementing conventional surgery and, hopefully, avoiding the need for chemotherapy.

Pulsed near infrared light (shown in red) is shone onto a tumor (shown in white) that is encased in blood vessels. The tumor is imaged by multispectral optoacoustic tomography via the ultrasound emission (shown in blue) from the gold nanotubes. (credit: Jing Claussen/iThera Medical, Germany)

Pulsed near infrared light (shown in red) is shone onto a tumor (shown in white) that is encased in blood vessels. The tumor is imaged by multispectral optoacoustic tomography via the ultrasound emission (shown in blue) from the gold nanotubes. (credit: Jing Claussen/iThera Medical, Germany)

Gold nanotube schematic showing hollow interior (left) and transmission electron microscope image (right) (credit: Jeremy Freear/Advanced Functional Materials)

Gold nanotube schematic showing hollow interior (left) and transmission electron microscope image (right) (credit: Jeremy Freear/Advanced Functional Materials)

The scientists at the University of Leeds  made the first successful demonstration of the biomedical use of gold nanotubes in a mouse model of human cancer. They injected the gold nanotubes intravenously then shone a pulsed infrared laser beam. By adjusting the brightness of the laser pulse, the researchers were able to control whether the gold nanotubes were in imaging mode or cancer-destruction mode. In addition, beforehand, the researchers claim the nanotubes  can have their lengths adjusted in order to absorb a precise wavelength.

[SEE] How gold is made and how it got to our planet

In image-mode, the gold nanotubes absorbed the the energy from the laser pulse and generated  ultrasound. Using  multispectral optoacoustic tomography (MSOT), researchers then read the ultrasound waves and detected the gold nanotubes.

For cancer destruction, there were two options:

  • Use a stronger laser beam to rapidly raise the temperature in the vicinity of the nanotubes so that the temperature was high enough to destroy cancer cells.
  • Load the central hollow core of the nanotubes with a therapeutic payload.

Although gold is not particularly harmful to the body (unless you pass a certain threshold), the team coated the nanotubes with a  protective sodium polystyrenesulfonate (PSS) coating. Ultimately, the nanotubes are safely excreted from the body, after they meet their purpose.

“High recurrence rates of tumors after surgical removal remain a formidable challenge in cancer therapy. Gold nanotubes have the potential to enhance the efficacy of these conventional treatments by integrating diagnosis and therapy in one single system,” said  lead author Sunjie Ye, who is based in the School of Physics and Astronomy and the Leeds Institute for Biomedical and Clinical Sciences at the University of Leeds.

Findings appeared in Advanced Functional Materials

Photo: Umeå University

Carbon nanotubes may help increase the efficiency of tomorrow’s solar cells

Every time a new manufacturing or development technology concerning solar cells was introduced, the futurists and tech pundits were quick to hail the coming of a new generation. The first were the monocrystal silicon cells doped with Phosphorus and Boron in a pn-junction; these are expensive to produce, yet comprise 80% of the total solar panel market. The second generation cells are usually called thin-film solar cells because when compared to crystalline silicon based cells they are made from layers of semiconductor materials only a few micrometers thick. Such cells include amorphous silicon cells, polycristalline silicon or Copper Indium diSelenide (CIS) cells; these cells have a lower efficiency than the 1st generation, yet they compensate by being very cheap. The third generation of solar cells are the most efficient cells. These cells are made from new materials besides silicon, including silicon wires, solar inks using conventional printing press technologies, organic dyes, quantum dots and conductive plastics.

So, when will the fourth generation be upon us? Looking forward, some might imply that the new wave of solar cells might be comprised, among other, by carbon nanotubes. A lot of efforts have been infested into carbon nanotube research in the past decade or so. Concerning solar cells, scientists are particularly interested in these one dimensional nanoscale cylinders made of carbon atoms because they possess some unique properties. Nanotubes have a fantastic tensile strength and an exceptional electron mobility, which makes them ideal for use in solar cells where carrying charge is paramount.

Photo:  Umeå University

Photo: Umeå University

By providing a better charge carrying medium, carbon nanotubes can significantly increase cell efficiency. However, in order to obtain the highest performance for electronic applications, the carbon nanotubes must be assembled into a well-ordered network of interconnecting nanotubes. Manufacturing tech today isn’t the best in this respect, so previous efforts thus far have been unsatisfying.

Scientists at Umeå University in Sweden found a way, however, to engineer these nanotube networks in a manner that is practical. For the first time, the researchers show that carbon nanotubes can be engineered into complex network architectures, and with controlled nano-scale dimensions inside a polymer matrix. The method offers a high degree of control and involves using far less nanotubes compared to other conventional methods, making the process cheaper by reducing material-related costs.

“We have found that the resulting nano networks possess exceptional ability to transport charges, up to 100 million times higher than previously measured carbon nanotube random networks produced by conventional methods,” says Dr David Barbero, leader of the project and assistant professor at the Department of Physics at Umeå University.

The Umea research was published in the journal Advanced Materials. Other important developments in this area include the work of Stanford researchers on an all-carbon solar cell, which promises to dramatically reduce costs if proven efficient. While the present research discusses a polymer solution to building carbon nanotube networks, worth mention are the developments made at University of Illinois  where a group there found a way to solder carbon nanotubes together. The method basically allows researchers to arrange carbon nanotubes for use as transistors where they could be embedded into thin sheets of plastic or flat-panel displays, but it could find its uses in solar cells too.

Captioned above is the Stanford University developed transparent sensor, which is capable of stretching to great lengths without getting deformed. (c) Stanford University

Skin-like material that stretches and senses might bring the tactile to the artificial

Captioned above is the Stanford University developed transparent sensor, which is capable of stretching to great lengths without getting deformed. (c) Stanford University

Captioned above is the Stanford University developed transparent sensor, which is capable of stretching to great lengths without getting deformed. (c) Stanford University

In the new mobile information age where smartphones have become an ever common part of our lives, there seems to be a dominant trend which tends to incorporate interactive touch screen capabilities to more and more consumer electronics. It’s pretty clear that our electronics are getting smarter day by day – I, for one, am still waiting for the next generation of vacuums to outwit me – and as such, the demand for innovative interactive tech is high.

Researchers at Stanford University have made a great forward in this sense after they developed a highly ductile smart-material, filled with sensors, while has the capability to stretch and return to its original size without a problem; much like the human skin. The material is made out of two layers of sillicon, coated by extremely thin single-walled carbon nanotubes, which basically act like two parallel plates. When one of the layers is pressed, the distance between the layers becomes thinner, the capacity of the sensor is increased. Silicone can store electrical charge, and thus whenever this charge is modified by pressing the plates, it is quantified by the sensors which can correlate the charge to a pressure. Basically, the material can feel, or rather sense.

RELATED: Scientists create artificial muscles from nanotubes 

The highly important stretching ability is offered by the carbon nanotubes characteristics. After being sprayed on to the sillicone layer, they randomly positioned themselves. When they are tensioned, the nanotubes stretch orientating towards the stretch direction, only to revert to their exact initial position when released.

The stretchy sensor can detect a wide array of touches, according to Darren Lipomi, a postdoctoral researcher on the team. Just like skin, the material can sense whether it’s being pressed or pinched.

Applications are numerous, the most realistic example being the prosthetic industry. However, think of robots capable of extremely sensitive manipulations, instead of the stiff maneuvers conventional robots have today. You wouldn’t want to shake hands with a robotic arm, nowadays.

wired

Meet the nanobamas

nanobama

Meet the world’s tiniest portraits of an elected president ever; meet the nanobamas. Each ‘Obama’ is made up of about 150 million tiny carbon nanotubes, which is about how many Americans voted in this year’s presidential election.

nanobama

An assistant professor professor in the Department of Mechanical Engineering at the University of Michigan, John Hart, along with his colleagues created these 3D portraits to create some awareness in some topics which he thinks are underapreciated by the mainstream, such as nanotechnology.

“Developments like this are an excellent way to bring the concepts of nanotechnology to a broader audience,” said Hart. “Also, we thought it would be fun.”

According to them, it took only a Friday evening to finish them, less than it took to create the website for them.

nanobama

To create them, they used Shepard Fairey’s famous red, white and blue Obama poster, converted into a line drawing, shrunk it, then printed it on a glass plate to create a mask (they used a laser for this). After that, they shined ultraviolet light through the glass mask the resulted and printed it on a silicon waffer to create the pattern. After that, they just used a high temperature chemical reaction to grow the nanotubes.

Nanotubes seen inside living animals

 

nanotube

Carbon nanotubes (CNTs) are allotropes of carbon. Their strength and flexibility makes them useful in controlling other nanoscale structures, which suggests they will have an important role in nanotechnology engineering. They are also used in concrete where they increase the tensile strength, and halt crack propagation in elevators, bridges, circuits, magnets, transistors, and they are may also be useful as air pollution filter or water filter or even for hydrogen storage. Sept. 24 is the day in which U.S. scientists have captured the first optical images of carbon nanotubes inside a living organism. The scientists developed a near-infrared fluorescent imaging technology which detected nanotubes inside living fruit flies.

The study co-author Professor Bruce Weisman stated “Carbon nanotubes are much smaller than living cells and they give off fluorescent light in a way that researchers hope to harness to detect diseases earlier than currently possible,” and “In order to do that, we need to learn how to detect and monitor nanotubes inside living tissues, and we must also determine whether they pose any hazards to organisms.”

They have studied carbon nanotubes interacting with tissues of rabbits, mice and other animals but the first detection of nanotubes inside a living animal took place thanks to the fruit fly which is also called Drosophila melanogaster. It is the most studied and the most used model organism as it used in studies in genetics, physiology and life history evolution.