MIT researchers develop printable electronics

MIT engineers have developed a fast, reliable and relatively cheap process through which they can print electronic surfaces. In a paper published today in Science Advances, the researchers report that they have fabricated carbon nanotube stamps able to print electronic ink onto both rigid and flexible surfaces.

The key here is being able to print small enough transistors so that they can control individual pixels in high-resolution displays and touchscreens. This opens up a huge market for potential applications, although the full extent of this potential has not been gauged yet.

Sanha Kim, a postdoc in MIT’s departments of Mechanical Engineering and Chemical Engineering, is the lead author, and A. John Hart, the Mitsui Career Development Associate Professor in Contemporary Technology and Mechanical Engineering is the senior researcher.

“There is a huge need for printing of electronic devices that are extremely inexpensive but provide simple computations and interactive functions,” Hart says. “Our new printing process is an enabling technology for high-performance, fully printed electronics, including transistors, optically functional surfaces, and ubiquitous sensors.”

It’s not the first time something like this was attempted. Other teams have tried to print electronics using inkjet printing and rubber stamping techniques but results have generally been fuzzy – literally. Because the printing is very hard to control at small scales, the technique tends to produce “coffee-ring” botches, with the ink spilling outside the borders leading to incomplete or aberrant circuits.

“There are critical limitations to existing printing processes in the control they have over the feature size and thickness of the layer that’s printed,” Hart says. “For something like a transistor or thin film with particular electrical or optical properties, those characteristics are very important.”

This new technology uses “nanoporous” stamps to remedy that issue. Imagine a small, spongy stamp half the size of a normal fingernail, with pores thinner than the width of a human hair. These pores allow the “ink” to flow uniformly and ensure the printing precision and achieving very high resolution. The stamp itself is fabricated from carbon nanotubes – strong, microscopic sheets of carbon atoms, arranged in cylinders – arranged in forest-like patterns.

The end result looked promising, and then they tested the electronics, to ensure that everything works fine. The patterns turned out to be indeed highly conductive and they worked as proper circuits.

Now, researchers are looking at three things: the first is how this process can be scaled up. They’ve already done the first steps, with a printing machine, including a motorized roller, and various substrates. Initial results show that this process could be scaled up and brought to industrial standards.

“This would be a continuous industrial process, where you would have a stamp, and a roller on which you’d have a substrate you want to print on, like a spool of plastic film or specialized paper for electronics,” Hart says. “We found, limited by the motor we used in the printing system, we could print at 200 millimeters per second, continuously, which is already competitive with the rates of industrial printing technologies. This, combined with a tenfold improvement in the printing resolution that we demonstrated, is encouraging.”

The second thing is finding applications for this technology. There might be a small emerging market for printable electronics, but just how large the demand is remains to be seen. Lastly, the team is already looking at ways to make this technology even more advanced – especially through graphene.

“Another exciting next step is the integration of our printing technologies with 2-D materials, such as graphene, which together could enable new, ultrathin electronic and energy conversion devices,” Hart says.


Lithium-ion batteries: Capacity might be increased by 6 times

The team was able to show through neutron measurements made at the Institut Laue-Langevin in Grenoble, France, that lithium ions do not penetrate deeply into the silicon. During the charge cycle, a 20-nm anode layer develops containing an extremely high proportion of lithium. This means extremely thin layers of silicon would be sufficient to achieve the maximal load of lithium.

Lithium-ion batteries: Capacity might be increased by 6 times

Berlin, Germany | Posted on August 9th, 2016

Lithium-ion batteries provide laptops, smart phones, and tablet computers with reliable energy. However, electric vehicles have not gotten as far along with conventional lithium-ion batteries. This is due to currently utilised electrode materials such as graphite only being able to stably adsorb a limited number of lithium ions, restricting the capacity of these batteries. Semiconductor materials like silicon are therefore receiving attention as alternative electrodes for lithium batteries. Bulk silicon is able to absorb enormous quantities of lithium. However, the migration of the lithium ions destroys the crystal structure of silicon. This can swell the volume by a factor of three, which leads to major mechanical stresses.

Observation during charging cycle

Now a team from the HZB Institute for Soft Matter and Functional Materials headed by Prof. Matthias Ballauff has directly observed for the first time a lithium-silicon half-cell during its charging and discharge cycles. “We were able to precisely track where the lithium ions adsorb in the silicon electrode using neutron reflectometry methods, and also how fast they were moving”, comments Dr. Beatrix-Kamelia Seidlhofer, who carried out the experiments using the neutron source located at the Institute Laue-Langevin.

Lithium-rich layer of only 20 nanometer

She discovered two different zones during her investigations. Near the boundary to the electrolytes, a roughly 20-nm layer formed having extremely high lithium content: 25 lithium atoms were lodged among 10 silicon atoms. A second adjacent layer contained only one lithium atom for ten silicon atoms. Both layers together are less than 100 nm thick after the second charging cycle.

Theoretical maximum capacity

After discharge, about one lithium ion per silicon node in the electrode remained in the silicon boundary layer exposed to the electrolytes. Seidlhofer calculates from this that the theoretical maximum capacity of these types of silicon-lithium batteries lies at about 2300 mAh/g. This is more than six times the theoretical maximum attainable capacity for a lithium-ion battery constructed with graphite (372 mAh/g).

Less is more

These are substantial findings that could improve the design of silicon electrodes: very thin silicon films should be sufficient for adsorbing the maximum possible amount of lithium, which in turn would save on material and especially on energy consumed during manufacture – less is more

Oxford Nanoimaging to provide desktop super-resolution microscopes

ONI’s microscope, the Nanoimager, has the footprint of a desktop computer, is about 30 times smaller and significantly less expensive than current super-resolution microscopes, and it will be manufactured in the UK.

ONI have raised £1.2m in a seed funding round from Oxford Sciences Innovation plc, Oxford Technology Management and Oxford-based investors Barnaby Martin and George Robinson.

This super-resolution microscope – developed by an interdisciplinary team led by Professor Achillefs Kapanidis and PhD student, Bo Jing, at Oxford’s Department of Physics – uses precise, rapid imaging of single fluorescent molecules and sophisticated software to generate striking images which differentiate objects spaced as close as 20 nanometers, a distance 200 times smaller than the length of an E. coli bacterium. This high performance offers much sharper images of live cells than conventional optical microscopy which is limited by diffraction.

Professor Kapanidis said: “The new microscope will take single-molecule imaging out of physics labs and centralised facilities, and into the hands of the chemist, the biologist, the biotechnologist. It is not only an excellent instrument for super-resolution imaging, but also a versatile, user-friendly toolbox that will help new users innovate with single molecules as their new currency.”

The new microscope can also help study how the tiny “biological machines” within cells assemble or break down biological structures such as proteins. These powerful capabilities can be exploited to screen chemical libraries for drug discovery, and to develop new generations of biosensors for detecting pathogens or disease markers. “It will unlock the users’ imagination and creativity,” Kapanidis said, “I wish I had this when I was a graduate student.”

Oxford Nanoimaging CEO Jeremy Warren said: “With Oxford Nanoimaging, we aim to democratise the use of super-resolution microscopy. Scientists who don’t have a lab equipped with specialist physics kit and a large budget can still access the information this very powerful technology provides. We anticipate that by our second year, 90 per cent of sales will be to groups outside of the UK creating a strong exporting business.”

Isis Innovation managing director Linda Naylor said: “In 2014, three prominent physicists won the Nobel Prize in Chemistry for starting super-resolution fluorescence microscopy and “bringing optical microscopy into the nano-dimension”. This Oxford spinout will make this advance accessible across the scientific world.”


Gallium nitride nano-sized LEDs

In 2014, the Nobel Prize in physics was awarded for the discovery of the gallium-nitride-based blue-light LED and its use for new, efficient LED-based white lamps. The development efforts in this field, however, do not stop there. The active layers in this type of diode take up less than 1μm. This means that most of the material in planar LEDs now on the market, which are hundreds of micrometers thick, is not used. This provides a motivation to continue research on efficient LEDs with nanoscale dimensions.1
In the last few years, it has been shown that an efficient LED can be made as a 3D nanostructure, in which the active parts take up less than 1μm. This makes more efficient use of the materials involved and, at the same time, excludes structural defects that limit the LED performance from the active device volume. Nanometer-sized LED structures can take many different shapes, such as thin elongated wires, pyramids, cubes, or platelets. To grow each of these small objects, different sections—including contact layers and an active region where the light is produced—are used. Basic material properties, however, put constraints on what can be grown, which affects the choice of shape for the nano-LED. For visible-light LEDs, the III nitrides—gallium nitride (GaN), aluminum nitride, indium nitride, and their alloys—are very suitable since they offer bandgaps in the visible range of photon energies.
We have recently summarized the current status of the development of nanowire-based LEDs.1 These devices are mainly shaped like nanorods with hexagonal cross sections, where the different layers are grown in a concentric manner around a core section (see Figure 1). The active region that produces the light consists of indium gallium nitride (InGaN) quantum wells (QWs) on m-plane facets, where ‘m’ refers to a specific crystallography orientation. Such QWs do not suffer from any polarization fields since the m-plane is non-polar. All other layers in the structure—the core, underlayer, QW barrier layers, p-layer and p-contact layer—are grown from GaN. A disadvantage with this design is that emission wavelengths longer than green are difficult to produce because of limitations with incorporating indium in the m-plane. Furthermore, there is a large lattice misfit strain built into the active QW region for high concentrations of indium corresponding to long wavelengths. This eventually causes defects and a reduced radiative efficiency for the LED.

Figure 1. Top left: Electroluminescence from the first blue nanowire LED fabricated by Glo AB in April 2007. Bottom left: Blue, green, yellow, and red examples from current state-of-the-art nanowire LEDs, grown by Glo-USA Inc. in 2013. Center: Side-view of a scanning electron microscope (SEM) image, showing nanowire LEDs monolithically grown on a wafer of gallium nitride on silicon. The edge of the top contact layer is visible, and both the contacted and non-contacted LEDs can be seen. Right: SEM image illustrating the air-bridge process. Images provided courtesy of QuNano AB and Glo AB.1 p-GaN: p-Type gallium nitride. p-AlGaN: p-Type aluminum gallium nitride.

In our latest work,2 we aim to solve these problems. The main concept driving our research is the need to create a ternary InGaN alloy in the form of a fully relaxed and dislocation-free c-oriented micro-substrate, where ‘c’ refers to another crystallography orientation. Our basic idea is to use the c-plane for the growth of the main LED structure, which improves the indium incorporation, with the use of a pre-fabricated indium-containing c-facet. This provides an opportunity to extend the possible emission wavelengths towards the red (see Figure 2). To handle the polarization fields existing in the c-plane structures, all layers in the structure should be made of InGaN, thereby reducing the strain. Importantly, this also also relaxes the otherwise stringent limitation on the QW width (because of the piezoelectric field in the QWs), which is typical for planar c-plane structures.

Figure 2. Top left: Schematic side-view cross section of a red-emitting LED. Bottom left: Top-view SEM image of a vertically grown pn-junction. The scale bar indicates 250nm. Right: Electrically driven red-emitting LED for the structure shown to the left. n/p-InGaN: n-Type/p-Type indium gallium nitride. QW: Quantum well. SQW: Single QW.

In our work, we demonstrate how a unique sequence of growth and processing steps—initiated by a nanowire structure—enables the formation of c-oriented platelets of fully relaxed, still dislocation-free, InGaN micro-substrates. On top of these substrates, it is now possible to grow dislocation-free, more indium-rich InGaN QWs that are designed to emit throughout the green to red spectral range. We have not yet established the typical efficiency of these LEDs, but we estimate it to be a few percent at present. This is considerably better than for typical planar red LEDs, even though these efficiencies were reached without any real optimization efforts.

In summary, we have shown that InGaN-based nano-LED structures show promise for solving the problems associated with long-wavelength nitride LEDs. There is a demand for LEDs covering all visible wavelengths using the GaN-InGaN material system. The first applications of our device, which does not require very high output power from the LEDs, may be for display technology. In fact, we can fabricate InGaN nano-LEDs that emit at blue and green wavelengths in one processing step on the same wafer. This provides additional opportunities and flexibility for display design. In the future we aim to create a flat substrate on to which we can form an active QW with an even higher indium-concentration, corresponding to emission of longer wavelengths (e.g. green, yellow, and red).

Five ways nanotechnology is securing your future

The past 70 years have seen the way we live and work transformed by two tiny inventions. The electronic transistor and the microchip are what make all modern electronics possible, and since their development in the 1940s they’ve been getting smaller. Today, one chip can contain as many as 5 billion transistors. If cars had followed the same development pathway, we would now be able to drive them at 300,000mph and they would cost just £3 each.

But to keep this progress going we need to be able to create circuits on the extremely small, nanometre scale. A nanometre (nm) is one billionth of a metre and so this kind of engineering involves manipulating individual atoms. We can do this, for example, by firing a beam of electrons at a material, or by vaporising it and depositing the resulting gaseous atoms layer by layer onto a base.

The real challenge is using such techniques reliably to manufacture working nanoscale devices. The physical properties of matter, such as its melting point, electrical conductivity and chemical reactivity, become very different at the nanoscale, so shrinking a device can affect its performance. If we can master this technology, however, then we have the opportunity to improve not just electronics but all sorts of areas of modern life.

1. Doctors inside your body

Wearable fitness technology means we can monitor our health by strapping gadgets to ourselves. There are even prototype electronic tattoos that can sense our vital signs. But by scaling down this technology, we could go further by implanting or injecting tiny sensors inside our bodies. This would capture much more detailed information with less hassle to the patient, enabling doctors to personalise their treatment.

The possibilities are endless, ranging from monitoring inflammation and post-surgery recovery to more exotic applications whereby electronic devices actually interfere with our body’s signals for controlling organ function. Although these technologies might sound like a thing of the far future, multi-billion healthcare firms such as GlaxoSmithKline are already working on ways to develop so-called “electroceuticals”.

2. Sensors, sensors, everywhere

These sensors rely on newly-invented nanomaterials and manufacturing techniques to make them smaller, more complex and more energy efficient. For example, sensors with very fine features can now be printed in large quantities on flexible rolls of plastic at low cost. This opens up the possibility of placing sensors at lots of points over critical infrastructure to constantly check that everything is running correctly. Bridges, aircraft and even nuclear power plants could benefit.

3. Self-healing structures

If cracks do appear then nanotechnology could play a further role. Changing the structure of materials at the nanoscale can give them some amazing properties – by giving them a texture that repels water, for example. In the future, nanotechnology coatings or additives will even have the potential to allow materials to “heal” when damaged or worn. For example, dispersing nanoparticles throughout a material means that they can migrate to fill in any cracks that appear. This could produce self-healing materials for everything from aircraft cockpits to microelectronics, preventing small fractures from turning into large, more problematic cracks.

4. Making big data possible

All these sensors will produce more information than we’ve ever had to deal with before – so we’ll need the technology to process it and spot the patterns that will alert us to problems. The same will be true if we want to use the “big data” from traffic sensors to help manage congestion and prevent accidents, or prevent crime by using statistics to more effectively allocate police resources.

Here, nanotechnology is helping to create ultra-dense memory that will allow us to store this wealth of data. But it’s also providing the inspiration for ultra-efficient algorithms for processing, encrypting and communicating data without compromising its reliability. Nature has several examples of big-data processes efficiently being performed in real-time by tiny structures, such as the parts of the eye and ear that turn external signals into information for the brain.

Computer architectures inspired by the brain could also use energy more efficiently and so would struggle less with excess heat – one of the key problems with shrinking electronic devices further.

5. Tackling climate change

The fight against climate change means we need new ways to generate and use electricity, and nanotechnology is already playing a role. It has helped create batteries that can store more energy for electric cars and has enabled solar panels to convert more sunlight into electricity.

The common trick in both applications is to use nanotexturing or nanomaterials (for example nanowires or carbon nanotubes) that turn a flat surface into a three-dimensional one with a much greater surface area. This means that there is more space for the reactions that enable energy storage or generation to take place, so the devices operate more efficiently

In the future, nanotechnology could also enable objects to harvest energy from their environment. New nano-materials and concepts are currently being developed that show potential for producing energy from movement, light, variations in temperature, glucose and other sources with high conversion efficiency.

The ConversationReference:

PV Nano Cell and Their Sicrys Conductive Inks are Bringing Us One Step Closer to 3D Printed Electronics

The Sicrys family of conductive inks are based on technology that produce narrower conductive patterns with minimum waste results when used during digital inkjet printing. The inks were developed to be used for the mass production of printed electronics and that industry’s extremely demanding requirements. PV Nano Cell, the developer of advanced single-crystal nanometric conductive digital inks, and their dispersion technology is capable of producing some highly efficient electronics. Products made with the inks offer improved conductivity, superior electrical properties and produce less waste than traditionally manufactured electronics. The company has just introduced their new copper Sicrys conductive ink, which is actually the first copper-based nanometric solution available on the market.

Sicrys single crystal nanoparticle inks.

PV Nano Cell will be showing off their entire portfolio of Sicrys conductive inks to LOPEC 2016, the international printed electronics event being held in Munich, Germany on April 6th and 7th. Their new inks are a huge leap forward in the race to perfect the process of 3D printing electronics, and products made with them will have applications in computing, wearable devices and is likely to play a large role in the continued development of the Internet of Things. The Sicrys inks are expected to finally make the mass production of printed electronics possible, something that has never been viable previously.

“LOPEC 2016 will be particularly exciting, as 3D printed electronics are on the verge of becoming reality. 3D printed electronics with embedded electronics within the structural material will revolutionize the use of electronics and data usage. Printed electronics will soon become integrated into daily life, from customized electronics to medical devices,” explained PV Nano Cell CEO Fernando de la Vega.

Solar cells made with Sicrys inks.

The cost effective and sustainable Series inks will allow huge leaps forward in the manufacturing of things like mobile phone antennas and fully-functional printed circuit boards. The materials will lead to thinner and smaller smartphones and other Internet of Things connected devices. PV Nano Cell’s Sicrys conductive ink materials are made using single crystal nanoparticles, that are ideal for 3D printing on flexible materials like plastic, fabric or even paper. Their newly developed copper nanometric conductive ink offers the same high-grade performance of Sicrys silver ink but also offers exceptional cost-efficiency, making 3D printed electronics cheaper and more accessible to everyone.

3dp_pvnanocell_sicrys_inksFounded back in 2009, PV Nano Cell manufactures their Sicrys family of conductive inks for companies all over the world. In addition to the success that they are starting to find with the Sicrys materials, they also manufacture a full range of 3D printed electronics applications, 3D printed circuit boards, RFID, sensors and smartphone touchscreens. One of the largest parts of the company is their extensive R&D division which constantly seeks to push the current boundaries of technology further.

PV Nano Cell was recently awarded the IDTechEx 2015 for Best Development in Materials for 3D Printing. They will be featuring their industrial inkjet printing applications this year at LOPEC 2016. If you’re going to be in Munich then you can check out their technology on exhibit at Hall B0, Booth 109 at LOPEC (April 6th and 7th). And you can find out more about PV Nano Cell and their conductive ink materials by going to their website. Do you think these new inks will have an impact on electronics? DIscuss in the PV Nano Cell New 3D Printing Inks forum over at


Fighting superbugs with nanotechnology and light

A new tool is emerging in the fight against antibiotic-resistant bacterial disease. Beyond the global efforts to limit overuse and abuse of antibiotic drugs, nanomedicine is finding additional ways to attack these superbugs.

Nanoparticles, a million times smaller than a millimeter, are proving to be stable, easy to deliver and readily incorporated into cells.

In recent work, a group of researchers at the University of Colorado, of which I am a member, has used nanoscale quantum dots – minuscule semiconductor particles with specific light-absorption properties – to kill drug-resistant superbugs without harming the surrounding healthy tissue.

Once introduced into the body, the quantum dots do nothing until they are activated by having a light shined on them. Any visible light source (a lamp, room light or even sunlight) can be used for this. So far our research has focused on topical infections on the skin; deeper inside the body, brighter lights or more nanoparticles may be needed.

When activated by light, the quantum dots start generating electrons that attach to dissolved oxygen in the cells, creating radical ions. Those ions interrupt biochemical reactions which cells rely on for communication and basic life functions. In this way, we can target and kill very specific bacterial cells that cause illnesses.

The superbug threat

Antibiotics are used not just to treat active bacterial infections; they are also routinely given to patients undergoing surgery, and people with compromised immune systems from diseases like HIV and cancer.

Bacteria that are resistant to more than one antibiotic drug – or “superbugs,” as they are commonly called – infect more than 2 million Americans a year, and kill 23,000 of them. Globally, they kill more than 700,000 people each year.

Projections by a United Kingdom government research panel suggest that if unchecked, superbugs could kill more than 10 million people each year by 2050. That would far outpace all other major causes of death – including diabetes, cancer, diarrhea and road accidents. The economic cost is estimated at US$100 trillion by 2050.

Focusing on a target

There are other nano-scale medicines for fighting infectious bacteria. When exposed to light, they heat up, killing all cells around them – not just the disease-causing ones. They therefore require special tools such as proteins or antibodies that selectively stick to desired cell types, to deliver them to very specific locations. That in turn requires the ability to accurately identify target cells.

Our method is an improvement because it allows more specific targeting of cells to be treated. Quantum dots with different sizes and electrical properties can help create different disruptive ions. That can allow doctors to choose disruptors to kill invading bacteria without harming nearby healthy tissue.

The activated quantum dots upset the balance of chemical processes, called “reduction-oxidation” or “redox” for short, in disease-causing bacteria in order to kill them.

Using this method and only a normal light bulb, we were able to eliminate a broad range of antibiotic-resistant bacteria. The bacteria were provided to us in the form of actual clinical samples from the University of Colorado School of Medicine. They included some of the most dangerous drug-resistant infections: methicillin-resistant Staphylococcus aureus; extended-spectrum β-lactamase-producing Klebsiella pneumoniae and Salmonella typhimurium; multi-drug-resistant Escherichia coli; and carbapenem-resistant Escherichia coli.

We were also able to make nanoparticles with different reactions to light, including having no response or even improving cellular reproduction. Increasing the growth of superbugs is not desirable, but this discovery may allow us encourage the growth of useful bacteria, such as in bioreactors, which can help manufacture of biofuels and antibiotic drugs.

Taking the next steps

So far our work has been in test tubes in controlled labs; our next step is to study this technique in animals. If successful, this technology could boost the fight against multi-drug-resistant bacteria in the short term and well out into the future.

It might, for example, spur the creation of a new class of light-activated drugs, lead to development of special fabrics with LED lights for phototherapy, and even form the basis of self-disinfecting surfaces and medical equipment.

And while the bacteria will continue to evolve to seek survival, our ability to control the specific reaction of the quantum dots once activated could let us move more quickly in this fight where defeat is not an option.