Blood-Resistant Surgical Glue For Mending Broken Hearts
14 February 2014, 08:00
Categories: adhesives bionanotech--nanobiotech
Researchers at the Brigham and Women’s Hospital in Boston have developed a surgical glue with promising properties: it doesn’t dissolve in blood, and it’s rubbery enough to hold a seal inside a beating heart. The cardiac adhesive has been tested in mice and pigs and is being developed as a commercial product by French startup Gecko Biomedical.
The adhesive is called a hydrophobic light-activated adhesive, or HLLA. It is a stretchy, sticky rubber made out of two biomolecules: glycerol and sebacic acid. This HLLA can be applied in a liquid form, and then solidified after a few seconds of exposure to UV light. In its liquid state, it’s viscous and hydrophobic, so it won’t wash away.
Toward Nanoscale Three-Dimensional Printing
6 February 2014, 13:59
Categories: tools techniques
Fabrication of three-dimensional objects through direct deposition of functional materials – also called additive manufacturing – has been a subject of intense study in the area of macroscale manufacturing for several decades. These 3D printing techniques are reaching a stage where desired products and structures can be made independent of the complexity of their shapes – even bioprinting tissue is now in the realm of the possible.
Researchers at Seoul National University have now shown that nanoscale 3D objects, such as free-standing nanowalls, can by constructed by additive manufacturing. Applying such 3D printing concepts to nanotechnology could bring similar advantages to nano fabrication – speed, less waste, economic viability – than it is expected to bring to manufacturing technologies.
“Electrospinning that produces polymer nano jets is a relatively simple and inexpensive method to yield nanoscale fibers, but the fiber streams are so chaotic that control of individual fibers has been considered almost impossible,” says Ho-Young Kim. “In our recent work, we have shown that an electrospun polymer solution jet, which tends to become unstable as traveling in the air due to Coulombic repulsion, can be stably focused onto a thin metal electrode line.”
Nanostructured Paper Improves Solar Cell Performance
4 February 2014, 11:21
Categories: nanocomposites smt-energy-photovoltaic
Researchers at the University of Maryland and the University of Nebraska-Lincoln have reported a novel transparent paper substrate design optimized for solar cells. The team created a novel transparent paper made of pulp from pine wood that simultaneously achieves an ultrahigh transmittance (∼96%) and ultrahigh optical haze (∼60%).
“We demonstrated that simple lamination of transparent paper on solar cell devices can increase the devices’ efficiency by 10-20% due to its high optical transmittance and light scattering,” says Liangbin Hu.
Transmission haze is an important optical property for optoelectronic devices and refers to the percentage of light diffusely scattered through a transparent surface from the total light transmitted. Higher transmission haze improves the light absorption efficiency of solar cells.
“Whereas displays and touch screens need high clarity and low optical haze, this is a property preferably maximized in transparent substrates integrated into solar devices,” explains Hu. “This means that current commercial substrates are best suited for displays but are not optimized for solar cell devices. We developed a new paper-based on wood cellulose materials, which has both high optical transmittance and high optical haze.”
“We demonstrated this with an organic solar cell by simply laminating a piece of such transparent paper and observed its power conversion efficiency (PCE) increased from 5.34 to 5.88%,” says Hu. Additionally, the mechanical properties of paper – such as toughness and strength – are important for various applications.
E-Whiskers Serve As Highly Sensitive Tactile Sensors
4 February 2014, 09:29
Categories: sensors biomimicry
Researchers at the University of California (UC) Berkeley have created tactile sensors, from composite films of carbon nanotubes and silver nanoparticles, which are similar to the highly sensitive whiskers of cats and rats. These new e-whiskers respond to pressure as slight as a single Pascal, about the pressure exerted on a table surface by a dollar bill. Among their many potential applications is giving robots new abilities to “see” and “feel” their surrounding environment.
“Whiskers are hair-like tactile sensors used by certain mammals and insects to monitor wind and navigate around obstacles in tight spaces,” says the leader of this research Ali Javey. “Our electronic whiskers consist of high-aspect-ratio elastic fibers coated with conductive composite films of nanotubes and nanoparticles. In tests, these whiskers were 10 times more sensitive to pressure than all previously reported capacitive or resistive pressure sensors.”
Javey and his research group have been leaders in the development of e-skin and other flexible electronic devices that can interface with the environment. In this latest effort, they used a carbon nanotube paste to form an electrically conductive network matrix with excellent bendability. To this carbon nanotube matrix they loaded a thin film of silver nanoparticles that endowed the matrix with high sensitivity to mechanical strain.
“The strain sensitivity and electrical resistivity of our composite film is readily tuned by changing the composition ratio of the carbon nanotubes and the silver nanoparticles,” Javey says. “The composite can then be painted or printed onto high-aspect-ratio elastic fibers to form e-whiskers that can be integrated with different user-interactive systems.”
Javey notes that the use of elastic fibers with a small spring constant as the structural component of the whiskers provides large deflection and therefore high strain in response to the smallest applied pressures. As proof-of-concept, he and his research group successfully used their e-whiskers to demonstrate highly accurate 2D and 3D mapping of wind flow. In the future, e-whiskers could be used to mediate tactile sensing for the spatial mapping of nearby objects, and could also lead to wearable sensors for measuring heartbeat and pulse rate.
“Our e-whiskers represent a new type of highly responsive tactile sensor networks for real time monitoring of environmental effects,” Javey says. “The ease of fabrication, light weight and excellent performance of our e-whiskers should have a wide range of applications for advanced robotics, human-machine user interfaces, and biological applications.”
New, Inexpensive, Transparent, Projection Screen
3 February 2014, 13:39
Categories: nanoparticles nano-emissive-displays
A team from MIT, Harvard University, and the US Army Edgewood Chemical Biological Center, has developed a new approach to making transparent projection screens. Their result paves the way for a new class of transparent displays with many attractive features, including wide viewing angle, scalability to large size, and low cost.
The new approach to transparent displays relies on the design of nanoparticles that interact with a single color. Their method is relatively simple: the first step consists in tailoring nanoparticles that interact, or better resonate, with one single color and neglect all the others; they are capable of reflecting a single specific color but let all other wavelengths through. The second step incorporates these color-selective nanoparticles into a transparent material, such as glass.
The result is a material that lets most of the ambient light go through and therefore the glass appears transparent; however, by using a laser projector that sends a light beam of the specific color that is scattered by the embedded nanoparticles, one can obtain a high-resolution projected image. As a proof of concept the research team developed a screen that interacts preferentially with blue light.
“We wanted to create a transparent screen sensitive to the blue light of a laser projector” says Chia Wei Hsu. “To this extent we used nanoparticles that scattered the same hue of blue as the laser in the projector. The resonance wavelength, the interaction color of a nanoparticle, can be tuned to arbitrary colors. We picked silver based nanoparticles because they are common and because they perform better than other metals”.
The group mixed silver nanoparticles of the diameter of 62 nanometers with a water-soluble transparent polymer. They poured the solution into a frame and let it dry at room temperature, obtaining a screen of 25×25 centimeters (about 10×10 inches) and around 0.5 millimeters thick (two hundredths of an inch).
“The apparent color and brightness seem to be those of regular glass,” says Bo Zhen, “but the show begins when we project blue light. Look at our figure 2, the projection of the MIT logo is clearly visible on our screen, unlike regular glass.”
“We are excited about our transparent display, but we are already thinking of the next challenges,” adds Professor Marin Soljacic. “In principle, we could implement a full-color display by embedding three types of nanoparticles each scattering selectively red, green and blue. Alternatively, one could design a single nanoparticle with multiple resonances, like a tennis player who hits specific RGB balls, but the difficulty there lies in maintaining high transparency away from the selected red, green, and blue.”
Transparent screens have innumerable applications, from showing navigation data on car windshields and aircraft cockpit windows, to projecting information and figures on glass windows and eyeglasses, to advertising and retail.
As Professor John Joannopoulos points out, “A variety of transparent displays have been developed for specific applications and are already in commerce, but each of them has some limitations. Our design has several attractive features that could make it a suitable option in many fields.” Existing head-up displays used in navigation systems have a narrow viewing angle that limits the position of the viewer. Diffusive screens can cover large surfaces: they use light scattering but no color selectivity and therefore look “hazy,” less transparent. Electronic flat-panel displays with transparent electronics are difficult to scale to large size. Fluorescent screens, usable in principle in storefront glass windows or similar large surfaces, are difficult to make at high efficiency.
“There is growing interest in transparent displays and our approach could serve many purposes,” says Hsu, “our display is very transparent and easily scalable to large size; the projection has very high resolution and is visible from a wide angle; the design is efficient and has low production and maintenance cost. We spent less than ten dollars to build our sample!”
The resonant nanoparticle scattering technique has potential to lead to new developments and applications such as flexible and scrollable displays, 3D transparent screens, and peel-and-stick projection foils.
“Think of all the surfaces covered by windows,” concludes Soljacic, “it is a lot of space that is not fully used: when I stroll downtown and look at the glass of skyscrapers at night, or at the subway windows, I imagine all that we can project on them.”
Ultra-Flexible OTFT Arrays For Future Flexible Displays
3 February 2014, 13:16
The Centre for Process Innovation (CPI), a UK-based technology innovation centre, has developed a novel fabrication processes that allows Organic Thin Film Transistors (OTFT) to be bent to small radii (1 mm) without a significant reduction in device performance. The work demonstrates progress towards ultra-flexible Active Matrix Organic Light Emitting Diode (AMOLED) displays.
In order to achieve the tight bend radius, the multiple interfaces present in the device stack were optimized to allow good adhesion under the strains experienced in the bending test. The fabricated OTFTs were repeatedly bent (up to 10,000 times) to a radius of 1 mm, which equates to a strain of 2.5%. Minimal change in the turn on voltage and on current were observed for the elongated cycle test.
This demonstration of bend resistance in high performance OTFT devices is part of ongoing work to integrate these materials into active matrix backplanes for AMOLED. It is expected that within 2014 the first plastic based display demonstrators will be completed using OTFT in project ROBOLED, which has received funding through the Technology Strategy Board.
NanoHouse Shows Nano Paints Present No Health Risk
3 February 2014, 12:23
After 42 months a EU research project called NanoHouse has ended, and the finding is that nanoparticles in the paint used on building façades do not represent a particular health risk. In the course of a technology briefing, researchers discussed these results with specialists from the construction industry.
Five Swiss labs at EMPA were involved in the NanoHouse project, along with four other European research institutes and four industrial partners. The aim of the project was to investigate the opportunities and risks presented by the nanomaterials used in the surface coatings applied to building façades. For the first time, not only were freshly manufactured products studied to see if they set free nanoparticles, but also aged samples.
Silic Shirt Repels Liquids
2 February 2014, 17:48
Categories: superhydrophobicphilic designers
Entrepreneur Aamir Patel has developed a shirt that is made from a hydrophobic fabric. The shirt’s soft polyester fabric is layered with microscopic silica particles, but the shirt looks like a simple, form-fitting T-shirt you’d find in any clothing store until you see what happens when someone throws a glass of water on it. As an added bonus, since the material never retains any moisture for bacteria to grow, it’s also anti-microbial and doesn’t need to be washed as often as a result.
There are already some effective hydrophobic coatings on the market today, the most prominent being NeverWet, but these tend to change a fabric’s texture and rinse away in the wash. Patel says his own experience with NeverWet is what convinced him to create the Silic shirt.
According to Patel, the Silic shirt is just as comfortable as any other shirt and can be machine washed 80 times before its water-repelling properties are affected.
Printed Eye Cells Could Help Treat Blindness
2 February 2014, 17:36
Categories: bionanotech--nanobiotech tools
Researchers at the University of Cambridge used a standard inkjet printer to form layers of two types of cells taken from the retinas of rats, and showed that the process did not compromise the cells’ health or ability to survive and grow in culture. Inkjet printing has been used to deposit cells before, but this is the first time cells from an adult animal’s central nervous system have been printed.
The group hopes to develop the technology into a tool for generating new tissues that can be grown outside the eye and implanted in patients with retinal damage. Alternatively, the technique could potentially be used to insert cells directly into damaged retinas during ocular surgery, says Keith Martin, a professor of ophthalmology who led the research.
Whether such printed structures will actually work in the eye, though, remains an unanswered question. Not only must they survive, but they must integrate with the rest of the retina and ultimately connect to the brain via the optic nerve.
A Self-Propelled Bio-Bot Swims In Liquid
2 February 2014, 17:08
Categories: bionanotech--nanobiotech biomimicry
A team of engineers at the University of Illinois has developed a class of tiny bio-hybrid machines that swim like sperm, the first synthetic structures that can traverse the viscous fluids of biological environments on their own. “Micro-organisms have a whole world that we only glimpse through the microscope,” said team leader Taher Saif. “This is the first time that an engineered system has reached this underworld.”
The bio-bots are modeled after single-celled creatures with long tails called flagella – for example, sperm. The researchers begin by creating the body of the bio-bot from a flexible polymer. Then they culture heart cells near the junction of the head and the tail. The cells self-align and synchronize to beat together, sending a wave down the tail that propels the bio-bot forward.
This self-organization is a remarkable emergent phenomenon, Saif said, and how the cells communicate with each other on the flexible polymer tail is yet to be fully understood. But the cells must beat together, in the right direction, for the tail to move.
“It’s the minimal amount of engineering – just a head and a wire,” Saif said. “Then the cells come in, interact with the structure, and make it functional.”
The team also built two-tailed bots, which they found can swim even faster. Multiple tails also opens up the possibility of navigation. The researchers envision future bots that could sense chemicals or light and navigate toward a target for medical or environmental applications.
“The long-term vision is simple,” said Saif. “Could we make elementary structures and seed them with stem cells that would differentiate into smart structures to deliver drugs, perform minimally invasive surgery or target cancer?”
Biomimetic Glass Overcomes Brittleness By Bending
2 February 2014, 16:43
Normally when you drop a drinking glass on the floor it shatters. But in future, thanks to a technique developed at McGill University in Canada, when the same thing happens the glass is likely to simply bend and become slightly deformed. That’s because Prof. François Barthelat and his team have successfully taken inspiration from the mechanics of natural structures like seashells in order to significantly increase the toughness of glass.
“Mollusk shells are made up of about 95 per cent chalk, which is very brittle in its pure form,” says Barthelat. “But nacre, or mother-of-pearl, which coats the inner shells, is made up of microscopic tablets that are a bit like miniature Lego building blocks, is known to be extremely strong and tough, which is why people have been studying its structure for the past twenty years.”
Previous attempts to recreate the structures of nacre have proved to be challenging, according to Barthelat. “Imagine trying to build a Lego wall with microscopic building blocks. It’s not the easiest thing in the world.” Instead, what he and his team chose to do was to study the internal ‘weak’ boundaries or edges to be found in natural materials like nacre and then use lasers to engrave networks of 3D micro-cracks in glass slides in order to create similar weak boundaries. The results were dramatic.
The researchers were able to increase the toughness of glass slides (the kind of glass rectangles that get put under microscopes) 200 times compared to non-engraved slides. By engraving networks of micro-cracks in configurations of wavy lines in shapes similar to the wavy edges of pieces in a jigsaw puzzle in the surface of borosilicate glass, they were able to stop the cracks from propagating and becoming larger. They then filled these micro-cracks with polyurethane, although according to Barthelat, this second process is not essential since the patterns of micro-cracks in themselves are sufficient to stop the glass from shattering.
The researchers worked with glass slides simply because they were accessible, but Barthelat believes that the process will be very easy to scale up to any size of glass sheet, since people are already engraving logos and patterns on glass panels. He and his team are excited about the work that lies ahead for them.
“What we know now is that we can toughen glass, or other materials, by using patterns of micro-cracks to guide larger cracks, and in the process absorb the energy from an impact,” says Barthelat. “We chose to work with glass because we wanted to work with the archetypal brittle material. But we plan to go on to work with ceramics and polymers in future. Observing the natural world can clearly lead to improved man-made designs.”
3D Printed "Soil" Shows How Microbes Move Beneath Our Feet
2 February 2014, 16:27
Soil scientists at Abertay University, in the UK, are using 3D printing technology to find out, for the very first time, exactly what is going on in the world beneath our feet. The detailed plastic cubes are replicas of the structure of the soil, and are being used by the scientists as experimental systems in the lab.
By inserting microorganisms (such as fungi and bacteria) into the pore spaces within the plastic soil, the scientists can now observe how these microorganisms move through it, survive, find food sources and interact.
Carbon Nanotube Sponge Improves Water Clean-Up
1 February 2014, 14:36
Categories: filtration nanotubes-wires-fullerenes
Carbon nanotube (CNT) sponges, uniquely doped with sulphur, demonstrated a high capacity to absorb both wastewater and oil, potentially opening up the possibility of using the material in industrial accidents and oil spill clean-ups.
CNTs have been touted as excellent candidates for wastewater clean-up in the past, however problems have arisen when trying to handle the fine powders and eventually retrieve them from the water. But in the new study, researchers from the University of Roma, University of Nantes and University of L’Aquila, bulked up the CNTs to the necessary size by adding sulphur during the production process―the resulting sponge had an average length of 20 mm.
The addition of sulphur caused defects to form on the surface of the CNT sponges which then enabled ferrocene, which was also added during the production process, to deposit iron into tiny capsules within the carbon shells.
The presence of iron meant the sponges could be magnetically controlled and driven without any direct contact, easing the existing problem of trying to control CNTs when added onto the water’s surface.
Nanoparticles Self-Assemble Into Transparent, Conductive Film
1 February 2014, 14:31
Categories: nanoparticles membranes
Cima NanoTech of St. Paul, MN develops next-generation transparent conductive films; their SANTE® Technology is a nanoparticle dispersion that self-assembles into a random mesh-like network pattern when coated onto substrates, enabling transparent conductors. The silver nanoparticle technology can be transferred to various substrates such as polycarbonate, acrylic, polypropylene, glass, and semiconductor materials.
SANTE® Technology can be used for applications such as electromagnetic interference (EMI) shielding, touch, transparent heating, photovoltaic, flexible electronics, and OLED lighting. This video demonstration shows how SANTE® Technology self-assembles into a transparent conductive nanoparticle network.
Nanotubes Enable Photoresponsive Smart Curtains
1 February 2014, 14:25
Categories: nanocomposites smt-polymorphic-shape-shifters
University of California, Berkeley researchers have layered carbon nanotubes onto a plastic polycarbonate membrane to create a material that moves quickly in response to light. The researchers were able to tweak the size and chirality – referring to the left or right direction of twist – of the nanotubes to make the material react to different wavelengths of light.
The swaths of material they created, dubbed “smart curtains,” could bend or straighten in response to the flick of a light switch. “We envision these in future smart, energy-efficient buildings,” says Ali Javey. “Curtains made of this material could automatically open or close during the day.” Other potential applications include light-driven motors and robotics that move toward or away from light.
Carbon Nanotube Films Conduct Heat As Well As Metals
1 February 2014, 14:16
Categories: energy nanotubes-wires-fullerenes
Single-walled carbon nanotube films are not only mechanically flexible but they also conduct heat extremely well. This finding, from researchers at Stanford University, means that the films might be used in a variety of innovative surface technologies – ranging from solar cells to waste heat recovery systems in automobiles and even smart phones and tablets.
According to the scientists, the simulations and experiments described in their new work could help them engineer a variety of nanostructured materials based on aligned fibres and sheets that not only conduct heat well but also have the right mechanical properties. Such materials might find use in a host of energy conversion and thermal management applications – for example, cooling down portable devices.
Goodson and colleagues say that they are now busy extending their studies to metallic nanowires films and porous metal foams, both of which are resilient to high temperatures.
Supercritical Water Helps Start Fire
1 February 2014, 14:10
Astronauts on board the ISS are experimenting with a form of water that helps start fire. “We call it ‘supercritical water,’” says Mike Hicks of the Glenn Research Center in Ohio. “And it has some interesting properties.”
Water becomes supercritical when it compressed to a pressure of 217 atmospheres and heated above 373 ºC. Above that so-called critical point, ordinary H2O transforms into something that is neither solid, liquid, nor gas. It’s more of a “liquid-like gas.”
“When supercritical water is mixed with organic material, a chemical reaction takes place—oxidation.” Says Hicks. “It’s a form of burning without flames.”
This really comes in handy when you want to get rid of certain unpleasant materials—like sewage. Cities, corporate farms, ships at sea and manned spacecraft accumulate waste materials that could benefit from this kind of treatment.
“When we push a wet waste stream above the critical point, supercritical water breaks the bonds of the hydrocarbons. Then, they can react with oxygen.” In other words, the slurry ignites. Sometimes, hotspots in the slurry produce visible flame, but usually not. “This is a relatively clean form of burning that produces pure water and carbon dioxide, but none of the toxic products of ordinary fire.”
The results could have down-to-Earth applications. The US Navy has already started using supercritical water technologies to purify waste streams onboard some of their ships, while the City of Orlando has started a supercritical treatment plant for processing municipal sludge.
Bacterial Spores Bend Latex Sheet
31 January 2014, 17:05
Categories: bionanotech--nanobiotech smt-polymorphic-shape-shifters
A new type of electrical generator uses bacterial spores to harness the untapped power of evaporating water, according to research conducted at the Wyss Institute of Biologically Inspired Engineering at Harvard University. Its developers foresee electrical generators driven by changes in humidity from sun-warmed ponds and harbors.
Alternating the humidity between that of a humid, misty day and that of a dry, sunny one causes a spore-covered sheet of latex rubber to bend and straighten. A flexible, spore-covered material could be used as a humidity-driven actuator. Credit: Xi Chen/Columbia University.
Vanadium Dioxide Micro-Motor Much More Powerful Than Human Muscle
31 January 2014, 16:48
Categories: smt-polymorphic-shape-shifters NEMS--MEMS
Highly valued by the electronics industry, vanadium dioxide is an insulator at low temperatures but abruptly becomes a conductor at 67 degrees Celsius. This temperature-driven phase transition from insulator-to-metal is expected to one day yield faster, more energy-efficient electronic and optical devices. It is also an ideal candidate material for creating miniaturized, multi-functional motors and artificial muscles.
Berkeley Lab researchers have now demonstrated a vanadium dioxide-based robotic torsional muscle/motor that for its size is a thousand times more powerful than a human muscle. “We’ve created a micro-bimorph dual coil that functions as a powerful torsional muscle, driven thermally or electro-thermally by the phase transition of vanadium dioxide,” says physicist Junqiao Wu. “We achieve superior performance in power density and speed over the motors and actuators now used in integrated micro-systems.”
This video clip shows the micro-muscle functioning first in micro-catapult mode, throwing out an object, and then in micro-explosion mode, sensing a proximate object and reacting by pushing the object away.
Graphene Ink For Transparent, Flexible Electronics
31 January 2014, 16:29
Categories: nanotubes-wires-fullerenes coatings
Researchers at the UK’s University of Cambridge have developed a graphene-based ink with properties including flexibility, optical transparency, and electrical conductivity. A printed piano prototype, designed in collaboration with Novalia Limited, demonstrates the ink’s potential.
The keys of the transparent piano are made from graphene-based inks, which have been printed onto a plastic film. These keys, working as electrodes, are connected to a simple electronic circuit-board, a battery, and speaker. When a person touches the graphene electrode, the amount of electrical charge held in the key changes. This is then detected and redirected by the circuit to the speaker, creating the musical note.
The University of Cambridge researchers also developed a flexible prototype digital display in collaboration with Printed Electronics Limited. The display uses conventional printable materials, but with a transparent, electrically conductive graphene layer on top. The graphene layer is flexible and more conductive and transparent than the conventional polymer it replaces.