Tag Archives: letter-materials-tech

As a provider of process solutions for a broad range of applications, Oxford Instruments announced the development and launch of the SiC via plasma etch process using its high performance PlasmaPro100Polaris etch system. SiC is becoming an increasingly important material, particularly in the arena of high performance GaN RF devices using SiC as a substrate. A smooth via etch through the SiC is essential to enable these devices, and Oxford Instruments has developed the ideal solution for etching high quality SiC vias efficiently. Combined with a low damage GaN etch within the same hardware, the PlasmaPro100 Polaris offers a unique capability for GaN based RF device plasma etch processing requirements.

The technology developed offers several process capabilities suited to the SiC via application:

  • High SiC etch rate enabling maximum throughput
  • Smooth sidewalls for problem free post etch metallisation
  • High selectivity to underlying GaN layer giving a smooth, low damage stop onto the GaN device layers
  • Clamping of sapphire carriers using Oxford Instruments’ unique patented Electrostatic Clamp technology ensuring excellent sample temperature control and maximum yield
  • Capability of etching SiC and GaN in the same tool through advanced plasma source technology
  • High utilisation provided by long Mean Time Between Cleans (MTBC)

Dr Mark Dineen, Optoelectronics Product Manager at Oxford Instruments Plasma Technology says, “Our Applications specialists have spent significant time developing this SiC via etch process on the PlasmaPro100 Polaris etch system, enabling high selectivity and throughput amongst other benefits. These benefits will enable our customers to etch both SiC and GaN in the same tool through advanced plasma source technology.”

Oxford Instruments delivers plasma processing systems, and offers a library of over 6,000 process recipes, all backed by a global support and service network.

SEM showing smooth via etch through SiC

SEM showing smooth via etch through SiC

By Zvi Or-Bach, President & CEO, MonolithIC 3D Inc.

As we have predicted two and a half years back, the industry is bifurcating, and just a few products pursue scaling to 7nm while the majority of designs stay on 28nm or older nodes.

Our March 2014 blog Moore’s Law has stopped at 28nm has recently been re-confirmed. At the time we wrote: “From this point on we will still be able to double the amount of transistors in a single device but not at lower cost. And, for most applications, the cost will actually go up.” This reconfirmation can be found in the following IBS cost analysis table slide, presented at the early Sept FD-SOI event in Shanghai.

Gate costs continue to rise each generation for FinFETs, IBS predicts.

Gate costs continue to rise each generation for FinFETs, IBS predicts.

As reported by EE Times – Chip Process War Heats Up, and quoting Handel Jones of IBS “28nm node is likely to be the biggest process of all through 2025”.

IBS prediction was seconded by “Samsung executive showed a foil saying it believes 28nm will have the lowest cost per transistor of any node.” The following chart was presented by Samsung at the recent SEMICON West (2016).

Zvi 2

And even Intel has given up on its “every two years” but still claims it can keep reducing transistor cost. Yet Intel’s underwhelming successes as a foundry suggests otherwise. We have discussed it in a blog titled Intel — The Litmus Test, and it was essentially repeated by SemiWiki’s Apple will NEVER use Intel Custom Foundry!

This discussion seems academic now, as the actual engineering costs of devices in advanced nodes have shown themselves to be too expensive for much of the industry. Consequently, and as predicted, the industry is bifurcating, with a few products pursuing scaling to 7nm while the majority of designs use 28nm or older nodes.

The following chart derived from TSMC quarterly earnings reports was published last week by Ed Sperling in the blog Stepping Back From Scaling:

Zvi 3

Yes, the 50-year march of Moore’s Law has ended, and the industry is now facing a new reality.

This is good news for innovation, as a diversity of choices helps support new ideas and new technologies such as 3D NAND, FDSOI, MEMS and others. These technologies will enable new markets and products such as the emerging market of IoT.

A good opportunity to learn more about these new scaling technologies is the IEEE S3S ’16, to be held in the Hyatt Regency San Francisco Airport, October 10th thru 13th, 2016. It starts with 3D and FDSOI tutorials, the emerging technologies for the IC future. CEA Leti is scheduled to give an update on their CoolCube program, Qualcomm will present some of their work on monolithic 3D, and three leading researchers from an imec, MIT, and Korea university collaboration will present their work on advanced monolithic 3D integration technologies. Many other authors will discuss their work on monolithic 3DIC and its ecosystem, in addition to tracks focused on SOI, sub-VT and dedicated sessions on IoT.

It is the double helix, with its stable and flexible structure of genetic information, that made life on Earth possible in the first place. Now a team from the Technical University of Munich (TUM) has discovered a double helix structure in an inorganic material. The material comprising tin, iodine and phosphorus is a semiconductor with extraordinary optical and electronic properties, as well as extreme mechanical flexibility.

Flexible yet robust – this is one reason why nature codes genetic information in the form of a double helix. Scientists at TU Munich have now discovered an inorganic substance whose elements are arranged in the form of a double helix.

The substance called SnIP, comprising the elements tin (Sn), iodine (I) and phosphorus (P), is a semiconductor. However, unlike conventional inorganic semiconducting materials, it is highly flexible. The centimeter-long fibers can be arbitrarily bent without breaking.

“This property of SnIP is clearly attributable to the double helix,” says Daniela Pfister, who discovered the material and works as a researcher in the work group of Tom Nilges, Professor for Synthesis and Characterization of Innovative Materials at TU Munich. “SnIP can be easily produced on a gram scale and is, unlike gallium arsenide, which has similar electronic characteristics, far less toxic.”

Countless application possibilities

The semiconducting properties of SnIP promise a wide range of application opportunities, from energy conversion in solar cells and thermoelectric elements to photocatalysts, sensors and optoelectronic elements. By doping with other elements, the electronic characteristics of the new material can be adapted to a wide range of applications.

Due to the arrangement of atoms in the form of a double helix, the fibers, which are up to a centimeter in length can be easily split into thinner strands. The thinnest fibers to date comprise only five double helix strands and are only a few nanometers thick. That opens the door also to nanoelectronic applications.

“Especially the combination of interesting semiconductor properties and mechanical flexibility gives us great optimism regarding possible applications,” says Professor Nilges. “Compared to organic solar cells, we hope to achieve significantly higher stability from the inorganic materials. For example, SnIP remains stable up to around 500°C (930 °F).”

Just at the beginning

“Similar to carbon, where we have the three-dimensional (3D) diamond, the two dimensional graphene and the one dimensional nanotubes,” explains Professor Nilges, “we here have, alongside the 3D semiconducting material silicon and the 2D material phosphorene, for the first time a one dimensional material – with perspectives that are every bit as exciting as carbon nanotubes.”

Just as with carbon nanotubes and polymer-based printing inks, SnIP double helices can be suspended in solvents like toluene. In this way, thin layers can be produced easily and cost-effectively. “But we are only at the very beginning of the materials development stage,” says Daniela Pfister. “Every single process step still needs to be worked out.”

Since the double helix strands of SnIP come in left and right-handed variants, materials that comprise only one of the two should display special optical characteristics. This makes them highly interesting for optoelectronics applications. But, so far there is no technology available for separating the two variants.

Theoretical calculations by the researchers have shown that a whole range of further elements should form these kinds of inorganic double helices. Extensive patent protection is pending. The researchers are now working intensively on finding suitable production processes for further materials.

Interdisciplinary cooperation

An extensive interdisciplinary alliance is working on the characterization of the new material: Photoluminescence and conductivity measurements have been carried out at the Walter Schottky Institute of the TU Munich. Theoretical chemists from the University of Augsburg collaborated on the theoretical calculations. Researchers from the University of Kiel and the Max Planck Institute of Solid State Research in Stuttgart performed transmission electron microscope investigations. Mössbauer spectra and magnetic properties were measured at the University of Augsburg, while researchers of TU Cottbus contributed thermodynamics measurements.

Thiophene-fused polycyclic aromatic hydrocarbons (PAHs) are known to be useful as organic semiconductors due to their high charge transport properties. Scientists at Nagoya University have developed a short route to form various thiophene-fused PAHs by simply heating mono-functionalized PAHs with sulfur. This new method is expected to contribute towards the efficient development of novel thiophene-based electronic materials.

Nagoya, Japan – Dr. Lingkui Meng, Dr. Yasutomo Segawa, Professor Kenichiro Itami of the JST-ERATO Itami Molecular Nanocarbon Project, Institute of Transformative Bio-Molecules (ITbM) of Nagoya University and Integrated Research Consortium on Chemical Sciences, and their colleagues have reported in the Journal of the American Chemical Society, on the development of a simple and effective method for the synthesis of thiophene-fused PAHs.

Thiophene-fused PAHs are organic molecules composed of multiple aromatic rings including thiophene. Thiophene is a five-membered aromatic ring containing four carbon atoms and a sulfur atom. Thiophene-fused PAHs are known to be one of the most common organic semiconductors and are used in various electronic materials, such as in transistors, organic thin-film solar cells, organic electro-luminescent diodes and electronic devices. More recently, they have found use in wearable devices due to their lightweight and flexibility.

Thienannulation (thiophene-annulation) reactions, a transformation that makes new thiophene rings via cyclization, leads to various thiophene-fused PAHs. Most conventional thienannulation methods require the introduction of two functional groups adjacent to each other to form two reactive sites on PAHs before the cyclization can take place. Thus, multiple steps are required for the preparation of the substrates. As a consequence, a more simple method to access thiophene-fused PAHs is desirable.

A team led by Yasutomo Segawa, a group leader of the JST-ERATO project, and Kenichiro Itami, the director of the JST-ERATO project and the center director of ITbM, has succeeded in developing a simple and effective method for the formation of various thiophene-fused PAHs. They have managed to start from PAHs that have only one functional group, which saves the effort of installing another functional group, and have performed the thienannulation reactions using elemental sulfur, a readily available low cost reagent. The reactions can be carried out on a multigram scale and can be conducted in a one-pot two-step reaction sequence starting from an unfunctionalized PAH. This new approach can also generate multiple thiophene moieties in a single reaction. Hence, this method has the advantage of offering a significant reduction in the number of required steps and in the reagent costs for thiophene-fused PAH synthesis compared to conventional methods.

The researchers have shown that upon heating and stirring the dimethylformamide solution of arylethynyl group-substituted PAHs and elemental sulfur in air, they were able to obtain the corresponding thiophene-fused PAHs. The arylethynyl group consists of an alkyne (a moiety with a carbon-carbon triple bond) bonded to an aromatic ring. The reaction proceeds via a carbon-hydrogen (C-H) bond cleavage at the position next to the arylethynyl group (called the ortho-position) on PAHs, in the presence of sulfur. As the ortho-C-H bond on the PAH can be cleaved under the reaction conditions, prior functionalization (installation of a functional group) becomes unnecessary.

Arylethynyl-substituted PAHs are readily accessible by the Sonogashira coupling, which is a cross-coupling reaction to form carbon-carbon bonds between an alkyne and a halogen-substituted aromatic compound. The synthesis of thiophene-fused PAHs can also be carried out in one-pot, in which PAHs are subjected to a Sonogashira coupling to form arylethynyl-substituted PAHs, followed by direct treatment of the alkyne with elemental sulfur to induce thienannulation.

“Actually, we coincidentally discovered this reaction when we were testing different chemical reactions to synthesize a new molecule for the Itami ERATO project,” says Yasutomo Segawa, one of the leaders of this study. “At first, most members including myself felt that the reaction may have already been reported because it is indeed a very simple reaction. Therefore, the most difficult part of this research was to clarify the novelty of this reaction. We put in a significant amount of effort to investigate previous reports, including textbooks from more than 50 years ago as well as various Internet sources, to make sure that our reaction conditions had not been disclosed before,” he continues.

The team succeeded in synthesizing more than 20 thiophene-fused PAHs. They also revealed that multiple formations of thiophene rings of PAHs substituted with multiple arylethynyl groups could be carried out all at once. Multiple thiophene-fused PAHs were generated from three-fold and five-fold thienannulations, which generated triple thia[5]helicene (containing three thiophenes) and pentathienocorannulene (containing five thiophenes), respectively. The pentathienocorannulene was an unprecedented molecule that was synthesized for the first time.

“I was extremely happy when I was able to obtain the propeller-shaped triple thia[5]helicene and hat-shaped pentathienocorannulene, because I have always been aiming to synthesize exciting new molecules since I joined Professor Itami’s group,” says Lingkui Meng, a postdoctoral researcher who mainly conducted the experiments. “We had some problems in purifying the compounds but we were delighted when we obtained the crystal structures of the thiophene compounds, which proved that the desired reactions had taken place.”

“The best part of this research for me is to discover that our C-H functionalization strategy on PAHs could be applied to synthesize structurally beautiful molecules with high functionalities,” says Segawa. “The successful synthesis of a known high-performance organic semiconductive molecule, (2,6-bis(4-n-octylphenyl)- dithieno[3,2-b:2?,3?-d]thiophene (the lower right of Figure 4), from a relatively cheap substrate opens doors to access useful thiophene compounds in a rapid and cost-effective manner.”

“We hope that ongoing advances in our method may lead to the development of new organic electronic devices, including semiconductor and luminescent materials,” say Segawa and Itami. “We are considering the possibilities to make this reaction applicable for making useful thiophene-fused PAHs, which would lead to the rapid discovery and optimization of key molecules that would advance the field of materials science.”

Lomonosov MSU physicists found a way to “force” silicon nanoparticles to glow in response to radiation strongly enough to replace expensive semiconductors used in display business. According to Maxim Shcherbakov, researcher at the Department of Quantum Electronics of the Moscow State University and one of the authors of the study, the developed method considerably enhances the efficiency of nanoparticle photoluminescence.

The key term in the problem is photoluminescence — the process, when materials irradiated by visible or ultraviolet radiation start to respond with their own light, but in a different spectral range. In the study, the material glows red.

In some of the modern displays, semiconductor nanoparticles, or the so-called quantum dots, are used. In quantum dots, electrons behave completely unlike those in the bulk semiconductor, and it has long been known that quantum dots possess excellent luminescent properties. Today, for the purposes of quantum-dot based displays various semiconductors are used, i.e. CdSe, etc. These materials are toxic and expensive, and, therefore, researchers have long been scrutinizing the far cheaper and much more studied silicon. It is also suitable for such use in all respects except one — silicon nanoparticles vaguely respond to radiation, which is not appealing for optoelectronic industry.

Scientists all over the world were seeking to solve this problem since the beginning of the 1990’s, but until now no significant success has been achieved in this direction. The breakthrough idea about how to “tame” silicon originated in Sweden, at the Royal Institute of Technology, Kista. A post-doctoral researcher Sergey Dyakov (a graduate of the MSU Faculty of Physics and the first author of the paper) suggested placing an array of silicon nanoparticles in a matrix with a non-homogeneous dielectric medium and cover it with golden nanostripes.

‘The heterogeneity of the environment, as has been previously shown in other experiments, allows to increase the photoluminescence of silicon by several orders of magnitude due to the so-called quantum confinement,’ says Maxim Shcherbakov. ‘However, the efficiency of the light interaction with nanocrystals still remains insufficient. It has been proposed to enhance the efficiency by using plasmons (quasiparticle appearing from fluctuations of the electron gas in metals — ed). Plasmon lattice formed by golden nanostripes allow to “hold” light on the nanoscale, and allow a more effective interaction with nanoparticles located nearby, bringing its luminescence to an increase.’

The MSU experiments with samples of “gold-plated” matrix with silicon nanoparticles made in Sweden brilliantly confirmed the theoretical predictions – the UV irradiated silicon for the first time shone bright enough to be used it in practice.

The first author of the paper Sergey Dyakov will present the findings on The 10th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (September 17-22, Crete). The work was also published in the Physical Review B (“Optical properties of silicon nanocrystals covered by periodic array of gold nanowires”).

The researchers in Jonathan Claussen’s lab at Iowa State University (who like to call themselves nanoengineers) have been looking for ways to use graphene and its amazing properties in their sensors and other technologies.

Iowa State engineers are developing real-world, low-cost applications for graphene. CREDIT: Photos by Christopher Gannon/Iowa State University.

Iowa State engineers are developing real-world, low-cost applications for graphene. Credit: Photos by Christopher Gannon/Iowa State University.

Graphene is a wonder material: The carbon honeycomb is just an atom thick. It’s great at conducting electricity and heat; it’s strong and stable. But researchers have struggled to move beyond tiny lab samples for studying its material properties to larger pieces for real-world applications.

Recent projects that used inkjet printers to print multi-layer graphene circuits and electrodes had the engineers thinking about using it for flexible, wearable and low-cost electronics. For example, “Could we make graphene at scales large enough for glucose sensors?” asked Suprem Das, an Iowa State postdoctoral research associate in mechanical engineering and an associate of the U.S. Department of Energy’s Ames Laboratory.

But there were problems with the existing technology. Once printed, the graphene had to be treated to improve electrical conductivity and device performance. That usually meant high temperatures or chemicals – both could degrade flexible or disposable printing surfaces such as plastic films or even paper.

Das and Claussen came up with the idea of using lasers to treat the graphene. Claussen, an Iowa State assistant professor of mechanical engineering and an Ames Laboratory associate, worked with Gary Cheng, an associate professor at Purdue University’s School of Industrial Engineering, to develop and test the idea.

And it worked: They found treating inkjet-printed, multi-layer graphene electric circuits and electrodes with a pulsed-laser process improves electrical conductivity without damaging paper, polymers or other fragile printing surfaces.

“This creates a way to commercialize and scale-up the manufacturing of graphene,” Claussen said.

The findings are featured on the front cover of the journal Nanoscale‘s issue 35. Claussen and Cheng are lead authors and Das is first author. Additional Iowa State co-authors are Allison Cargill, John Hondred and Shaowei Ding, graduate students in mechanical engineering. Additional Purdue co-authors are Qiong Nian and Mojib Saei, graduate students in industrial engineering.

Two major grants are supporting the project and related research: a three-year grant from the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 11901762 and a three-year grant from the Roy J. Carver Charitable Trust. Iowa State’s College of Engineering and department of mechanical engineering are also supporting the research.

The Iowa State Research Foundation Inc. has filed for a patent on the technology.

“The breakthrough of this project is transforming the inkjet-printed graphene into a conductive material capable of being used in new applications,” Claussen said.

Those applications could include sensors with biological applications, energy storage systems, electrical conducting components and even paper-based electronics.

To make all that possible, the engineers developed computer-controlled laser technology that selectively irradiates inkjet-printed graphene oxide. The treatment removes ink binders and reduces graphene oxide to graphene – physically stitching together millions of tiny graphene flakes. The process makes electrical conductivity more than a thousand times better.

“The laser works with a rapid pulse of high-energy photons that do not destroy the graphene or the substrate,” Das said. “They heat locally. They bombard locally. They process locally.”

That localized, laser processing also changes the shape and structure of the printed graphene from a flat surface to one with raised, 3-D nanostructures. The engineers say the 3-D structures are like tiny petals rising from the surface. The rough and ridged structure increases the electrochemical reactivity of the graphene, making it useful for chemical and biological sensors.

All of that, according to Claussen’s team of nanoengineers, could move graphene to commercial applications.

“This work paves the way for not only paper-based electronics with graphene circuits,” the researchers wrote in their paper, “it enables the creation of low-cost and disposable graphene-based electrochemical electrodes for myriad applications including sensors, biosensors, fuel cells and (medical) devices.”

Last March, the artificial intelligence (AI) program AlphaGo beat Korean Go champion LEE Se-Dol at the Asian board game.

“The game was quite tight, but AlphaGo used 1200 CPUs and 56,000 watts per hour, while Lee used only 20 watts. If a hardware that mimics the human brain structure is developed, we can operate artificial intelligence with less power,” points out Professor YU Woo Jong.

In the junctions (synapses) between neurons, signals are transmitted from one neuron to the next. TRAM is made by a stack of different layers: A semiconductor molybdenum disulfide (MoS2) layer with two electrodes (drain and source), an insulating hexagonal boron nitride (h-BN) layer and graphene layer. This two-terminal architecture simulates the two neurons that made up to the synaptic structure. When the difference in the voltage of the drain and the source is sufficiently high, electrons from the drain electrode tunnel through the insulating h-BN and reach the graphene layer. Memory is written when electrons are stored in the graphene layer, and it is erased by the introduction of positive charges in the graphene layer. CREDIT: IBS

In the junctions (synapses) between neurons, signals are transmitted from one neuron to the next. TRAM is made by a stack of different layers: A semiconductor molybdenum disulfide (MoS2) layer with two electrodes (drain and source), an insulating hexagonal boron nitride (h-BN) layer and graphene layer. This two-terminal architecture simulates the two neurons that made up to the synaptic structure. When the difference in the voltage of the drain and the source is sufficiently high, electrons from the drain electrode tunnel through the insulating h-BN and reach the graphene layer. Memory is written when electrons are stored in the graphene layer, and it is erased by the introduction of positive charges in the graphene layer. CREDIT: IBS

In collaboration with Sungkyunkwan University, researchers from the Center for Integrated Nanostructure Physics within the Institute for Basic Science (IBS), have devised a new memory device inspired by the neuron connections of the human brain. The research, published in Nature Communications, highlights the devise’s highly reliable performance, long retention time and endurance. Moreover, its stretchability and flexibility makes it a promising tool for the next-generation soft electronics attached to clothes or body.

The brain is able to learn and memorize thanks to a huge number of connections between neurons. The information you memorize is transmitted through synapses from one neuron to the next as an electro-chemical signal. Inspired by these connections, IBS scientists constructed a memory called two-terminal tunnelling random access memory (TRAM), where two electrodes, referred to as drain and source, resemble the two communicating neurons of the synapse. While mainstream mobile electronics, like digital cameras and mobile phones use the so-called three-terminal flash memory, the advantage of two-terminal memories like TRAM is that two-terminal memories do not need a thick and rigid oxide layer. “Flash memory is still more reliable and has better performance, but TRAM is more flexible and can be scalable,” explains Professor Yu.

TRAM is made up of a stack of one-atom-thick or a few atom-thick 2D crystal layers: One layer of the semiconductor molybdenum disulfide (MoS2) with two electrodes (drain and source), an insulating layer of hexagonal boron nitride (h-BN) and a graphene layer. In simple terms, memory is created (logical-0), read and erased (logical-1) by the flowing of charges through these layers. TRAM stores data by keeping electrons on its graphene layer. By applying different voltages between the electrodes, electrons flow from the drain to the graphene layer tunnelling through the insulating h-BN layer. The graphene layer becomes negatively charged and memory is written and stored and vice versa, when positive charges are introduced in the graphene layer, memory is erased.

IBS scientists carefully selected the thickness of the insulating h-BN layer as they found that a thickness of 7.5 nanometers allows the electrons to tunnel from the drain electrode to the graphene layer without leakages and without losing flexibility.

Flexibility and stretchability are indeed two key features of TRAM. When TRAM was fabricated on flexible plastic (PET) and stretachable silicone materials (PDMS), it could be strained up to 0.5% and 20%, respectively. In the future, TRAM can be useful to save data from flexible or wearable smartphones, eye cameras, smart surgical gloves, and body-attachable biomedical devices.

Last but not least, TRAM has better performance than other types of two-terminal memories known as phase-change random-access memory (PRAM) and resistive random-access memory (RRAM).

Two scientists at the University of Central Florida have discovered how to get a solid material to act like a liquid without actually turning it into liquid, potentially opening a new world of possibilities for the electronic, optics and computing industries.

When chemistry graduate student Demetrius A. Vazquez-Molina took COF-5, a nano sponge-like, non-flammable manmade material and pressed it into pellets the size of a pinkie nail, he noticed something odd when he looked at its X-ray diffraction pattern. The material’s internal crystal structure arranged in a strange pattern. He took the lab results to his chemistry professor Fernando Uribe-Romo, who suggested he turn the pellets on their side and run the X-ray analysis again.

The result: The crystal structures within the material fell into precise patterns that allow for lithium ions to flow easily – like in a liquid.

The findings, published in the Journal of the American Chemical Society earlier this summer, are significant because a liquid is necessary for some electronics and other energy uses. But using current liquid materials sometimes is problematic.

For example, take lithium-ion batteries. They are among the best batteries on the market, charging everything from phones to hover boards. But they tend to be big and bulky because a liquid must be used within the battery to transfer lithium ions from one side of the battery to the other. This process stores and disperses energy. That reaction creates heat, which has resulted in cell phones exploding, hover boards bursting into flames, and even the grounding of some airplanes a few years ago that relied on lithium batteries for some of its functions.

But if a nontoxic solid could be used instead of a flammable liquid, industries could really change, Uribe-Romo said.

“We need to do a lot more testing, but this has a lot of promise,” he said. “If we could eliminate the need for liquid and use another material that was not flammable, would require less space and less packaging, that could really change things. That would mean less weight and potentially smaller batteries.”

Smaller, nontoxic and nonflammable materials could also mean smaller electronics and the ability to speed up the transfer of information via optics. And that could mean innovations to communication devices, computing power and even energy storage.

“This is really exciting for me,” said Vazquez-Molina who was a pre-med student before taking one of Uribe-Romo’s classes. “I liked chemistry, but until Professor Romo’s class I was getting bored. In his class I learned how to break all the (chemistry) rules. I really fell in love with chemistry then, because it is so intellectually stimulating.”

Uribe-Romo has his high school teacher in Mexico to thank for his passion for chemistry. After finishing his bachelor’s degree at Instituto Tecnológico y de Estudios Superiores de Monterrey in Mexico, Uribe-Romo earned a Ph.D. at the University of California at Los Angeles. He was a postdoctoral associate at Cornell University before joining UCF as an assistant professor in 2013.

The findings were pursued by a team lead by Uribe-Romo in collaboration with scientists at UCLA’s Department of Chemistry and Biochemistry. It’s a partnership the team is pursuing to see if COF-5 is indeed the material that could revolutionize battery and mobile device industries.

Applying an electric field to some materials causes their atoms to “switch” their electric polarization from one direction to another, making one side of the material positive and the other negative. This switching property of “ferroelectric” materials allows them to be used in a wide range of applications. For example, ferroelectric capacitors are used to store binary bits of data in memory devices.

The newly synthesized crystal is ferroelectric above room temperature (a-b, e-f) and turns into "plastic phase", meaning highly deformable, at higher temperature (a to c). The electric polarity of each molecule can be aligned in one direction by applying electric field as it cools (c to e). Credit: Harada J. et al., July 11, 2016, Nature Chemistry, DOI: 10.1038/NCHEM.2567

The newly synthesized crystal is ferroelectric above room temperature (a-b, e-f) and turns into “plastic phase”, meaning highly deformable, at higher temperature (a to c). The electric polarity of each molecule can be aligned in one direction by applying electric field as it cools (c to e). Credit: Harada J. et al., July 11, 2016, Nature Chemistry, DOI: 10.1038/NCHEM.2567

Researchers at Japan’s Hokkaido University have developed a novel ferroelectric plastic crystal that could accelerate the development of more flexible, cost-efficient and less toxic ferroelectrics than those currently in use.

The crystal is ferroelectric above room temperature, then turns into a plastic, more pliable phase at higher temperatures. At the higher temperatures, the molecules in the crystal have randomly different polarity axes, but they can be aligned in one direction by applying an electric field as the crystal cools, bringing it back to a ferroelectric state.

Being able to control the polarity in this manner addresses a major challenge previously faced by researchers working with organic compound-based ferroelectric crystals. These are less symmetric than inorganic crystals, and can thus be polarized only in one direction leading to a very weak overall polarization of randomly oriented crystals.

A distinct advantage of this particular crystal is its transition to a plastic state when heat is applied. This plasticity – as opposed to fracturing that occurs in regular organic and inorganic crystals when a mechanical stress is applied – makes it extremely advantageous for use as a thin ferroelectric film in devices, such as non-volatile ferroelectric random-access memory devices, which maintain memory when the power is turned off.

Exploring crystals composed of molecules similar to quinuclidine could lead to the discovery of more ferroelectric crystals, write the researchers in their paper published in the journal Nature Chemistry. Chemical modifications of the molecules’ constituent ions could also improve their performance, the researchers add.

If you’ve never had the plumber to your house, you’ve been lucky. Pipes can burst due to a catastrophic event, like subzero temperatures, or time and use can take a toll, wearing away at the materials with small dings and dents that aren’t evident until it’s too late.

But what if there were a way to identify those small, often microscopic failures before you had to call for help?

The Autonomous Materials Systems (AMS) Group at the Beckman Institute for Advanced Science and Technology has recently found a new way to identify microscopic damage in polymers and composite materials before total failure occurs.

Colorless, non-fluorescent microcapsules use a type of fluorescence called aggregation-induced emission (AIE), which becomes brighter as the indicator solidifies from solution and is visible under ultraviolet (UV) light. Credit: Autonomous Materials Systems Group, Beckman Institute for Advanced Science and Technology, University of Illinois

Colorless, non-fluorescent microcapsules use a type of fluorescence called aggregation-induced emission (AIE), which becomes brighter as the indicator solidifies from solution and is visible under ultraviolet (UV) light.
Credit: Autonomous Materials Systems Group, Beckman Institute for Advanced Science and Technology, University of Illinois

“Autonomous indication of small cracks has exciting potential to make structures safer and more reliable by giving time to intervene and repair or replace the damaged region prior to catastrophic failure,” said Nancy Sottos, professor of materials science and engineering, and one of the authors of “A Robust Damage-Reporting Strategy for Polymeric Materials Enabled by Aggression-Induced Emission,” recently published in ACS Central Science. The paper is part of a research project selected as a finalist for the Institution of Chemical Engineers (IChemE) Global Awards 2016.

The researchers sequestered fluids containing turn-on fluorescence indicators in microcapsules, and then incorporated them into polymeric materials.

“We’ve developed microcapsules that are colorless and non-fluorescent when intact,” said Maxwell Robb, Beckman Institute Postdoctoral Fellow and a lead author on the paper. “We can embed them into materials, and when damage occurs, the microcapsules will release their payload and become fluorescent, indicating that repair is needed.”

Previous work led by Wenle Li, a postdoctoral research associate and co-first author of the study, had investigated another type of indicator within microcapsules, which underwent a chemical reaction upon release to produce a color change. However, the nature of the chemical reaction limited the system to a narrow range of materials.

The new method uses a type of fluorescence called aggregation-induced emission (AIE), which becomes brighter as the indicator solidifies from solution and is visible under ultraviolet (UV) light. The unique mechanism of indication, which relies on a physical change of state instead of a chemical reaction, enables excellent performance in a wide variety of materials and for visualizing different types of damage.

“The elegance of this system lies in its versatility as well as its sensitivity,” said Li. “We can easily visualize a fluorescence signal resulting from mechanical damage as small as two microns.”

The research is funded by BP, which is interested in coating oil and gas pipelines with a polymer coating that will be able to indicate damage. The goal is to target damage at its earliest stage to prevent further deterioration, improve safety and reliability, and reduce life cycle costs associated with regular maintenance and inspection.

Using instruments in Beckman’s Microscopy Suite, the group was able to study the microcapsules and coatings of various materials, image them, and correlate the fluorescence signals to 3D structures of the damaged coatings.

“This is incredibly interdisciplinary work,” said Robb. “Having knowledge about the aggregation-induced emission effect, and being able to design the chemistry of the microcapsule system was the starting point. Then there is the actual application of this technology into materials and coatings, which relies heavily on the expertise within materials science and engineering.”

The AMS Group includes Sottos, Jeffrey Moore, professor of chemistry, and Scott White, professor of aerospace engineering, who also co-authored the study. Their work has led to new discoveries in self-detecting and self-healing materials.

“To impact the coatings industry, materials with self-reporting capability must meet a few criteria: they must be simple, not change the way the materials are traditionally applied, and perform just as well,” said Moore. “Our approach hits this target – the new self-reporting function is realized by just one simple additive.”

The next steps for this research are to combine damage indication with self-healing materials.

“If you could couple this technology that lets you know that damage has occurred with a self-healing material that tells you when the damage has been healed, it could be really powerful,” said Robb.

“We have developed both turn-on fluorescence and color-changing indication systems. Our vision is to combine these multi-channel strategies to enable materials that monitor their mechanical integrity throughout the entire polymer lifecycle,” said Li.