‘Nano-Spidey senses’ could help autonomous machines (EV’s, Drones) see better


spideysenses (1)Researchers are building spider-inspired sensors into the shells of autonomous drones and cars so that they can detect objects better. Credit: Taylor Callery

What if drones and self-driving cars had the tingling “spidey senses” of Spider-Man?

They might actually detect and avoid objects better, says Andres Arrieta, an assistant professor of mechanical engineering at Purdue University, because they would process  faster.

Better sensing capabilities would make it possible for drones to navigate in dangerous environments and for cars to prevent accidents caused by human error. Current state-of-the-art sensor technology doesn’t process data fast enough—but nature does.

And researchers wouldn’t have to create a radioactive spider to give autonomous machines superhero sensing abilities.

Instead, Purdue researchers have built  inspired by spiders, bats, birds and other animals, whose actual spidey senses are  linked to special neurons called mechanoreceptors.

The nerve endings—mechanosensors—only detect and process information essential to an animal’s survival. They come in the form of hair, cilia or feathers.

“There is already an explosion of data that  can collect—and this rate is increasing faster than what conventional computing would be able to process,” said Arrieta, whose lab applies principles of nature to the design of structures, ranging from robots to aircraft wings.

“Nature doesn’t have to collect every piece of data; it filters out what it needs,” he said.

Many biological mechanosensors filter data—the information they receive from an environment—according to a threshold, such as changes in pressure or temperature.

'Spidey senses' could help autonomous machines see better
In nature, ‘spidey-senses’ are activated by a force associated with an approaching object. Researchers are giving autonomous machines the same ability through sensors that change shape when prompted by a predetermined level of force. Credit: ETH Zürich images/Hortense Le Ferrand

A spider’s hairy mechanosensors, for example, are located on its legs. When a spider’s web vibrates at a frequency associated with prey or a mate, the mechanosensors detect it, generating a reflex in the spider that then reacts very quickly. The mechanosensors wouldn’t detect a lower frequency, such as that of dust on the web, because it’s unimportant to the spider’s survival.

The idea would be to integrate similar sensors straight into the shell of an autonomous machine, such as an airplane wing or the body of a car. The researchers demonstrated in a paper published in ACS Nano that engineered mechanosensors inspired by the hairs of spiders could be customized to detect predetermined forces. In real life, these forces would be associated with a certain object that an autonomous machine needs to avoid.

But the sensors they developed don’t just sense and filter at a very fast rate—they also compute, and without needing a power supply.

“There’s no distinction between hardware and software in nature; it’s all interconnected,” Arrieta said. “A sensor is meant to interpret data, as well as collect and filter it.”

In nature, once a particular level of force activates the mechanoreceptors associated with the hairy mechanosensor, these mechanoreceptors compute information by switching from one state to another.

Purdue researchers, in collaboration with Nanyang Technology University in Singapore and ETH Zürich, designed their sensors to do the same, and to use these on/off states to interpret signals. An intelligent machine would then react according to what these sensors compute.

These artificial mechanosensors are capable of sensing, filtering and computing very quickly because they are stiff, Arrieta said. The sensor material is designed to rapidly change shape when activated by an external force. Changing shape makes conductive particles within the material move closer to each other, which then allows electricity to flow through the sensor and carry a signal. This signal informs how the autonomous system should respond.

“With the help of machine learning algorithms, we could train these sensors to function autonomously with minimum energy consumption,” Arrieta said. “There are also no barriers to manufacturing these sensors to be in a variety of sizes.”


Explore further

Engineers create new design for ultra-thin capacitive sensors


More information: Hortense Le Ferrand et al, Filtered Mechanosensing Using Snapping Composites with Embedded Mechano-Electrical Transduction, ACS Nano (2019). DOI: 10.1021/acsnano.9b01095

Journal information: ACS Nano
Provided by Purdue University
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KAUST – Putting the ‘Sense’ in Materials – Say Goodbye to Batteries as You Know Them


KAUST 5c6a94542b7e32661e7f8b63An interdisciplinary initiative is helping KAUST be at the forefront of a digital revolution, where sensors can find a use just about anywhere.

 

The ability to track minuscule but important changes across a range of systems—from the body to the borough and beyond—seems limitless with the emerging array of novel devices that are tiny, self-powering and wirelessly connected. KAUST’s Sensor Initiative comprises a broad range of experts, from marine scientists to electrical engineers, who are innovating solutions to some of the most challenging obstacles in sensor technology. Together, they are powering up to transform the exciting intersection between small interconnected devices and the world around us.

Capacity to monitor our surroundings also reveals new potential in environmental and community protection. For example, a sensor that can detect a flood or a fire can save lives; a sensor that can track animals could help to better manage an ecosystem; and a sensor that can read plant condition could promote sustainable farming.

To take advantage of the market opportunities for sensors in both medical and environmental fields, KAUST holds an annual meeting of biologists, engineers and chemists to discuss technology development. Since 2015, these meetings have produced ambitious collaborations that aim to improve the science that underpins next-gen sensors as well as to take them to the market.

Get ready to plug and play

Khaled Salama, professor of electrical engineering and director of the Sensor Initiative, explains that what sets KAUST apart are the University’s human resources and outstanding lab facilities that underpin its innovative sensor technologies. With the onslaught of data coming from the hundreds of billions of sensors in our cities, cars, homes and offices, we need machine learning to help us understand the data, the supercomputing power to manage it and the expertise to make sure the machines do it all effectively.

“KAUST has strength in materials research, which is where our expertise can be used for developing sensors with transducer components that can be quickly swapped out and replaced with ones customized for different biological or environmental applications,” says Salama.

“Some can stick to your skin and monitor your vital signs through changes in your sweat while others can be placed in petroleum installations to monitor hazardous gases,” says Salama. “We’re not bound to one specific application, and each new development gives us a chance to answer some fundamental scientific questions along the way.”

Say goodbye to batteries, as you know them

KAUST is deploying tiny sensors across the University’s campus to model future smart cities that can continuously monitor air quality or help self-driving cars navigate. Implementing this vision means making devices that are as self-sufficient as possible.

“If you have sensors containing regular batteries, they might last a thousand cycles,” says Husam Alshareef, professor of materials science. “We have to get them to last millions of times longer.”

Alshareef and several international collaborators are building a technology known as microsupercapacitors—next-generation batteries—to resolve challenges around energy storage. Through a special vacuum deposition process, the team has transformed ruthenium oxide into a thin-film electrode that can hold massive amounts of charge and quickly release it on demand.

Get plant smart with winged sensors

Professor Muhammad Hussain is a strong believer in the importance of availability in the sensor market. He insists that his sensors not only provide solutions to everyday problems but also that they be affordable to all. That said, he does not forgo creativity for affordability. Hussain’s plant sensors are flexible, inexpensive and range in size from 1-20 mm in diameter. When placed on a plant leaf, they can detect temperature, humidity and growth, data that can be used to help farmers farm smart—minimizing nutrient and water waste. But what makes them especially remarkable is their beautiful butterfly shape. When asked why he chose the butterfly shape Hussain told us, “Butterflies are aesthetically beautiful and natural in a plant environment. Their large wings allow us to integrate many different sensors, which is especially useful for the artificial intelligence chip we are currently integrating into the system. Ultimately, we aim to create a fully interactive system such that the butterfly can deliver nutrients or gather more data.”

KAUST 4 5cad09dcc58d3a5aa53e57ab

Sherjeel Khan, ph.D. student with Mohammed Hussain, fabricates the plant-monitoring sensors shaped like butterflies. © 2018 KAUST

Learn to talk effectively

One of the advanced sensors being developed at KAUST is the smart bandage from the group of Atif Shamim in the electrical engineering program. This gadget uses carbon-based transducers to directly contact chronic wounds and to predict signs of infection based on blood pH levels.

Shamim notes that wireless communication is crucial if sensors and other components of the Internet of things are to be integrated with everyday items. His team has pioneered the use of low-energy Bluetooth radio networks to help connect smart devices with each other and also with network servers.

“Even though the Internet of things is about inanimate objects, they have to make decisions for you,” says Shamim. “They need to sense and they need to communicate.”

KAUST 5c6a94542b7e32661e7f8b63

Shamim’s smart bandage may help to predict signs of infection in a wound by reading blood pH levels. © 2018 KAUST 

Be prepared to dive deep

Shamim is partnering with other KAUST researchers, including Jürgen Kosel, who specializes in using the property of magnetism in his sensor work to track animal behavior in the Red Sea. The team created stickers—each containing a self-powered, Bluetooth-connected position sensor—that are small enough to be attached to crabs, turtles and giant clams in the Red Sea.

Kosel and his group aimed to tackle the primary challenge associated with remote tracking of marine life—the tendency for water to scatter the radiofrequency waves used by most sensors for geolocation. Working with the KAUST Nanofabrication Core Lab to fabricate thin-film structures, the team created flexible sensors that reveal their global position using magnetic signals that easily access subsurface environments.

“Magnetic fields can penetrate many materials without affecting them, and that includes humans and other animals,” says Kosel. “We’ve shown that you can even derive how much energy a marine animal consumes using magnetic sensors that monitor water flow.”

Sense the future of sensors

For the Emeritus Senior Vice President for Research, Jean Frechet, the possibilities are great: “With our expertise and resources, we have built bridges across disciplines by bringing together researchers from KAUST and other institutions. They inspire each other to solve challenges as diverse as the survival of marine life, communications for the 21st century, and the exploitation of big data. The KAUST Sensor Initiative will stimulate the next generation and contribute to diversifying the country’s economy as we design and engineer sensors that collect the data we need to address global challenges.”

 

Update Rice University – Researchers develop a method to make atom-flat sensors that seamlessly integrate with devices – technique will make active sensors or devices possible for telecommunication and bio-sensing, plasmonics


Rice U Flat Atom structure DuEfkhxWwAAfEGTRice University engineers have developed a method to transfer complete, flexible, two-dimensional circuits from their fabrication platforms to curved and other smooth surfaces. Such circuits are able to couple with near-field …more

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by  scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices to report on what they perceive.

Electronically active 2-D materials have been the subject of much research since the introduction of graphene in 2004. Even though they are often touted for their strength, they’re difficult to move to where they’re needed without destroying them.Nano Sensor 1 FANG

The Ajayan and Lou groups, along with the lab of Rice engineer Jacob Robinson, have a new way to keep the materials and their associated circuitry, including electrodes, intact as they’re moved to curved or other smooth surfaces.

The results of their work appear in the American Chemical Society journal ACS Nano.

Rice logo_rice3The Rice team tested the concept by making a 10-nanometer-thick indium selenide photodetector with gold electrodes and placing it onto an . Because it was so close, the near-field sensor effectively coupled with an evanescent field—the oscillating electromagnetic wave that rides the surface of the fiber—and accurately detected the flow of information inside.

The benefit is that these sensors can now be imbedded into such fibers where they can monitor performance without adding weight or hindering the signal flow.

“This paper proposes several interesting possibilities for applying 2-D devices in real applications,” Lou said. “For example, optical fibers at the bottom of the ocean are thousands of miles long, and if there’s a problem, it’s hard to know where it occurred. If you have these sensors at different locations, you can sense the damage to the fiber.”

Lou said labs have gotten good at transferring the growing roster of 2-D materials from one surface to another, but the addition of electrodes and other components complicates the process. “Think about a transistor,” he said. “It has source, drain and gate electrodes and a dielectric (insulator) on top, and all of these have to be transferred intact. That’s a very big challenge, because all of those materials are different.”

Raw 2-D materials are often moved with a layer of polymethyl methacrylate (PMMA), more commonly known as Plexiglas, on top, and the Rice researchers make use of that technique. But they needed a robust bottom layer that would not only keep the circuit intact during the move but could also be removed before attaching the device to its target. (The PMMA is also removed when the circuit reaches its destination.)

The ideal solution was poly-dimethyl-glutarimide (PMGI), which can be used as a device fabrication platform and easily etched away before transfer to the target. “We’ve spent quite some time to develop this sacrificial layer,” Lou said. PMGI appears to work for any 2-D material, as the researchers experimented successfully with molybdenum diselenide and other materials as well.

Nano sensors 2 electronics_vision_10-11-17

The Rice labs have only developed passive sensors so far, but the researchers believe their technique will make active  or devices possible for telecommunication, biosensing, plasmonics and other applications.

 Explore further: Fluorine flows in, makes material metal

More information: Zehua Jin et al, Near-Field Coupled Integrable Two-Dimensional InSe Photosensor on Optical Fiber, ACS Nano (2018). DOI: 10.1021/acsnano.8b07159

 

NIST Research Suggests Graphene Can Stretch to be a Tunable Ion Filter – Applications for nanoscale sensors, drug delivery and water purification


 

 

Researchers at the National Institute of Standards and Technology (NIST) have conducted simulations suggesting that graphene, in addition to its many other useful features, can be modified with special pores to act as a tunable filter or strainer for ions (charged atoms) in a liquid.

The concept, which may also work with other membrane materials, could have applications such as nanoscale mechanical sensors, drug delivery, water purification and sieves or pumps for ion mixtures similar to biological ion channels, which are critical to the function of living cells. The research is described in the November 26 issue of Nature Materials.

“Imagine something like a fine-mesh kitchen strainer with sugar flowing through it,” project leader Alex Smolyanitsky said. “You stretch that strainer in such a way that every hole in the mesh becomes 1-2 percent larger. You’d expect that the flow through that mesh will be increased by roughly the same amount. Well, here it actually increases 1,000 percent. I think that’s pretty cool, with tons of applications.”

If it can be achieved experimentally, this graphene sieve would be the first artificial ion channel offering an exponential increase in ion flow when stretched, offering possibilities for fast ion separations or pumps or precise salinity control. Collaborators plan laboratory studies of these systems, Smolyanitsky said.

Graphene is a layer of carbon atoms arranged in hexagons, similar in shape to chicken wire, that conducts electricity. The NIST molecular dynamics simulations focused on a graphene sheet 5.5 by 6.4 nanometers (nm) in size and featuring small holes lined with oxygen atoms. These pores are crown ethers—electrically neutral circular molecules known to trap metal ions. A previous NIST simulation study showed this type of graphene membrane might be used for nanofluidic computing.

In the simulations, the graphene was suspended in water containing potassium chloride, a salt that splits into potassium and chlorine ions. The crown ether pores can trap potassium ions, which have a positive charge. The trapping and release rates can be controlled electrically. An electric field of various strengths was applied to drive the ion current flowing through the membrane.

Researchers then simulated tugging on the membrane with various degrees of force to stretch and dilate the pores, greatly increasing the flow of potassium ions through the membrane. Stretching in all directions had the biggest effect, but even tugging in just one direction had a partial effect.

Researchers found that the unexpectedly large increase in ion flow was due to a subtle interplay of a number of factors, including the thinness of graphene; interactions between ions and the surrounding liquid; and the ion-pore interactions, which weaken when pores are slightly stretched. There is a very sensitive balance between ions and their surroundings, Smolyanitsky said.

The research was funded by the Materials Genome Initiative.


Paper: A. Fang, K. Kroenlein, D. Riccardi and A. Smolyanitsky. Highly mechanosensitive ion channels from graphene-embedded crown ethers. Nature Materials. Published online November 26, 2018. DOI: 10.1038/s41563-018-0220-4

Israeli scientists develop ‘Cancer-Sniffing Nose’ using Nanotechnology – new device can ‘smell’ 17 diseases on a person’s breath


 

Nano Nose 2 nanose2-900x497

London audience told by Israeli-Christian professor about a new device which can ‘smell’ 17 diseases on a person’s breath

Professor Hossam Haick, an Israeli Christian, delivered Technion UK’s Ron Arad lecture at the Royal College of Physicians last week.

The electronic ‘nose’ he developed can smell 17 diseases on a person’s breath, including Alzheimer’s, Parkinson’s, tuberculous, diabetes and lung cancer.Cancer Nose I 140715155737-na-nose-face-story-top

The non-intrusive medical device, which works by identifying as disease’s bio-markers, has attracted the attention of billionaires such as Bill and Melinda Gates, whose foundation focuses on the diagnostics of diseases.

“Every disease has a unique signature – a ‘breath print,’” Haick said. “The challenge is to bring the best science we have proven into reality by developing a smaller device that captures all the components of a disease appearing in the breath.”

Cancer Sniffing Nose The-Technion-Ron-Arad-Dinner-The-Technion-UK_Prof_Hosaim-Haick_Cancer-Sniffing_Nose_Lecture-2-635x357Haick works at the Department of Chemical Engineering and the Russell Berrie Nanotechnology Institute at the Technion in Israel and is an expert in the field of nanotechnology and non-invasive disease diagnosis. (Left) Professor Hossam Haick at the Technion Ron Arad Dinner Credit: John Rifkin

The University said the latest advances in his research mean that it has the potential to identify diseases though sensors in mobile phones and wearable technology, and with more analysis and data it may even be able to predict cancer in the future.

“We cannot develop this technology in Israel without developing the best science,” he said. “Integrating the software, machine learning and academic intelligence will make a critical change in the early detection and prevention of cancerous diseases.”

US Patent Granted to Grolltex for Advanced Graphene ‘Super’ Sensor


December 8, 2017

San Diego based Grolltex was granted a patent by the USPTO for a new multi-modal ‘super’ sensor design made of single layer graphene.

The patent, titled “Graphene-based multi-modal sensor” describes a one atom thick architecture and utilizes several of Grolltex’ 2D materials technologies to produce what the company internally calls ‘The smallest, most sensitive sensor in the world’.

The company is working on initial applications for these sensors that are targeting the bio-sensing and defense fields as leading-edge users of this technology.

“Our single atom thick sensor design, in the strain sensor configuration, is so sensitive that it captures a robust and repeatable signal on the contractility strength of individual ‘cardio myocytes’ or heart cells as they beat”, said Jeff Draa, company co-founder and CEO.

“This can be a holy grail for fields such as cardiotoxicity testing as it has the capacity to be a significant time and money saver in the new drug testing and approval process”.

Additionally, the single layer graphene sensor covered by this patent has a very high threshold for thermal coefficient of resistance, meaning it experiences little to no signal drift when exposed to extreme levels of heat. This makes it an ideal sensor for measuring micro strain in high speed aeronautical vehicles.

These sensors are so small and thin, they can be layered into the skins of airplanes, helicopters or other high stress vehicles to real-time measure and detect micro stress at architectures and levels not currently possible with today’s sensing technologies. These sensors could also be discreetly placed within critical structures such as bridges or buildings.

The full story is available below.

Source: The Daily Telescope

MIT: Nanosensors could help determine tumors’ ability to remodel tissue – Nanosensors that can ‘profile’ tumors


mit-nanosensorsc-093016MIT researchers have designed nanosensors that can profile tumors and may yield insight into how they will respond to certain therapies. Credit: Christine Daniloff/MIT

MIT researchers have designed nanosensors that can profile tumors and may yield insight into how they will respond to certain therapies. The system is based on levels of enzymes called proteases, which cancer cells use to remodel their surroundings.

Once adapted for humans, this type of sensor could be used to determine how aggressive a tumor is and help doctors choose the best treatment, says Sangeeta Bhatia, the John and Dorothy Wilson Professor of Health Sciences and Technology and Electrical Engineering and Computer Science and a member of MIT’s Koch Institute for Integrative Cancer Research.

“This approach is exciting because people are developing therapies that are protease-activated,” Bhatia says. “Ideally you’d like to be able to stratify patients based on their protease activity and identify which ones would be good candidates for these therapies.”

Once injected into the tumor site, the nanosensors are activated by a  that is harmless to healthy tissue. After interacting with and being modified by the target tumor proteins, the sensors are secreted in the urine, where they can be easily detected in less than an hour.

Bhatia and Polina Anikeeva, the Class of 1942 Associate Professor of Materials Science and Engineering, are the senior authors of the paper, which appears in the journal Nano Letters. The paper’s lead authors are Koch Institute postdoc Simone Schurle and graduate student Jaideep Dudani.

Heat and release

Tumors, especially aggressive ones, often have elevated protease levels. These enzymes help tumors spread by cleaving proteins that compose the extracellular matrix, which normally surrounds cells and holds them in place.

In 2014, Bhatia and colleagues reported using nanoparticles that interact with a type of protease known as matrix metalloproteinases (MMPs) to diagnose cancer. In that study, the researchers delivered nanoparticles carrying peptides, or short protein fragments, designed to be cleaved by the MMPs. If MMPs were present, hundreds of cleaved peptides would be excreted in the urine, where they could be detected with a simple paper test similar to a pregnancy test.

In the new study, the researchers wanted to adapt the sensors so that they could report on the traits of tumors in a known location. To do that, they needed to ensure that the sensors were only producing a signal from the target organ, unaffected by background signals that might be produced in the bloodstream. They first designed sensors that could be activated with light once they reached their target. That required the use of ultraviolet light, however, which doesn’t penetrate very far into tissue.

“We started thinking about what kinds of energy we might use that could penetrate further into the body,” says Bhatia, who is also a member of MIT’s Institute for Medical Engineering and Science.

To achieve that, Bhatia teamed up with Anikeeva, who specializes in using magnetic fields to remotely activate materials. The researchers decided to encapsulate Bhatia’s protease-sensing nanoparticles along with magnetic particles that heat up when exposed to an alternating magnetic field. The field is produced by a small magnetic coil that changes polarity some half million times per second.

The heat-sensitive material that encapsulates the particles disintegrates as the magnetic particles heat up, allowing the protease sensors to be released. However, the particles do not produce enough heat to damage nearby tissue.

“It has been challenging to examine tumor-specific protease activities from patients’ biofluids because these proteases are also present in blood and other organs,” says Ji Ho (Joe) Park, an associate professor of bio and brain engineering at the Korea Advanced Institute of Science and Technology.

“The strength of this work is the magnetothermally responsive protease nanosensors with spatiotemporal controllability,” says Park, who was not involved in the research. “With these nanosensors, the MIT researchers could assay protease activities involved more in tumor progression by reducing off-target activation significantly.”

Choosing treatments

In a study of mice, the researchers showed that they could use these particles to correctly profile different types of colon tumors based on how much protease they produce.

Cancer treatments based on proteases, now in clinical trials, consist of antibodies that target a tumor protein but have “veils” that prevent them from being activated before reaching the tumor. The veils are cleaved by proteases, so this therapy would be most effective for patients with high  levels.

The MIT team is also exploring using this type of sensor to image cancerous lesions that spread to the liver from other organs. Surgically removing such lesions works best if there are fewer than four, so measuring them could help doctors choose the best treatment.

Bhatia says this type of sensor could be adapted to other tumors as well, because the magnetic field can penetrate deep into the body. This approach could also be expanded to make diagnoses based on detecting other kinds of enzymes, including those that cut sugar chains or lipids.

Explore further: Nanoparticles amplify tumor signals, making them much easier to detect in the urine

More information: Simone Schuerle et al. Magnetically Actuated Protease Sensors for in Vivo Tumor Profiling, Nano Letters (2016). DOI: 10.1021/acs.nanolett.6b02670

 

 

University of Cambridge and IBM Collaborate on “Something Deep Within” ~ Nanocrystals grown in nanowires for new classes of high-performance, energy-efficient computing, communications, and environmental and medical sensing systems.


Deep Nanowires 081116 160729143208_1_540x360Top: High-resolution electron microscopy images of a nickel silicide rhombic nanocrystal embedded in a silicon nanowire prepared with gold silicide used as a catalyst. The images demonstrate the intimate interactions that arise at the interfaces of these nanomaterials. Bottom: The physical properties that arise from such complex nano-systems could be used in next-generation photodetectors, lasers, and transistors.
Credit: Image courtesy of Department of Energy, Office of Science
 

As any good carpenter knows, it’s often easier to get what you want if you build it yourself. An international team using resources at the Center for Functional Nanomaterials took that idea to heart. They wanted to tailor extremely small wires that carry light and electrons. They devised an approach that lets them tailor the wires through exquisite control over the structures at the nanoscale. New structures could open up a potential path to a wide range of smaller, lighter, or more efficient devices.

This development could lead to highly tailored nanowires for new classes of high-performance, energy-efficient computing, communications, and environmental and medical sensing systems. The resulting devices could lead to smaller electronics as well as improving solar panels, photodetectors, and semiconductor lasers.

Semiconducting nanowires have a wide range of existing and potential applications in optoelectronic materials, from single-electron transistors and tunnel diodes, to light-emitting semiconducting nanowires to energy-harvesting devices. An international collaboration led by the University of Cambridge and IBM has demonstrated a new method to create novel nanowires that contain nanocrystals embedded within them. They accomplished this by modifying the classic “vapor-liquid-solid” crystal growth method, wherein a liquid-phase catalyst decomposes an incoming gas-phase source and mediates the deposition of the solid, growing nanowire.

In this work, a bimetallic catalyst is used. The team showed that by appropriate thermal treatment, it is possible to crystallize a solid silicide structure within the liquid catalyst, and then attach the nanowire to the solid silicon in a controlled epitaxial fashion. The Center for Functional Nanomaterials’ Electron Microscopy Facility was employed to image the nanomaterials by high spatial-resolution, aberration-corrected transmission electron microscopy. As well, scientists used a first-of-its-kind direct electron detector to obtain high temporal-resolution images of the fabrication process. Incorporating these instruments with the expertise and insight of the scientific team led to fantastic, nanoscale control over these structures and presents notable potential for a broad range of potential devices, like photodetectors and single electron transistors.


Story Source:

The above post is reprinted from materials provided byDepartment of Energy, Office of Science. Note: Content may be edited for style and length.


Journal Reference:

  1. F. Panciera, Y.-C. Chou, M. C. Reuter, D. Zakharov, E. A. Stach, S. Hofmann, F. M. Ross. Synthesis of nanostructures in nanowires using sequential catalyst reactions. Nature Materials, 2015; 14 (8): 820 DOI:10.1038/nmat4352

Research: “Flexible ‘Nano-Skin’ for “Cloaking” Objects


Iowa Cloak Skin 110528_web

IMAGE: This flexible, stretchable and tunable “meta-skin ” can trap radar waves and cloak objects from detection. view more  Credit: Liang Dong/Iowa State University

Iowa State University engineers have developed a new flexible, stretchable and tunable “meta-skin” that uses rows of small, liquid-metal devices to cloak an object from the sharp eyes of radar.

The meta-skin takes its name from metamaterials, which are composites that have properties not found in nature and that can manipulate electromagnetic waves. By stretching and flexing the polymer meta-skin, it can be tuned to reduce the reflection of a wide range of radar frequencies.

The journal Scientific Reports recently reported the discovery online. Lead authors from Iowa State’s department of electrical and computer engineering are Liang Dong, associate professor; and Jiming Song, professor. Co-authors are Iowa State graduate students Siming Yang, Peng Liu and Qiugu Wang; and former Iowa State undergraduate Mingda Yang. The National Science Foundation and the China Scholarship Council have partially supported the project.

“It is believed that the present meta-skin technology will find many applications in electromagnetic frequency tuning, shielding and scattering suppression,” the engineers wrote in their paper.

Dong has a background in fabricating micro and nanoscale devices and working with liquids and polymers; Song has expertise in looking for new applications of electromagnetic waves.

Working together, they were hoping to prove an idea: that electromagnetic waves – perhaps even the shorter wavelengths of visible light – can be suppressed with flexible, tunable liquid-metal technologies.

What they came up with are rows of split ring resonators embedded inside layers of silicone sheets. The electric resonators are filled with galinstan, a metal alloy that’s liquid at room temperature and less toxic than other liquid metals such as mercury.

Those resonators are small rings with an outer radius of 2.5 millimeters and a thickness of half a millimeter. They have a 1 millimeter gap, essentially creating a small, curved segment of liquid wire.

The rings create electric inductors and the gaps create electric capacitors. Together they create a resonator that can trap and suppress radar waves at a certain frequency. Stretching the meta-skin changes the size of the liquid metal rings inside and changes the frequency the devices suppress.

Tests showed radar suppression was about 75 percent in the frequency range of 8 to 10 gigahertz, according to the paper. When objects are wrapped in the meta-skin, the radar waves are suppressed in all incident directions and observation angles.

“Therefore, this meta-skin technology is different from traditional stealth technologies that often only reduce the backscattering, i.e., the power reflected back to a probing radar,” the engineers wrote in their paper.

As he discussed the technology, Song took a tablet computer and called up a picture of the B-2 stealth bomber. One day, he said, the meta-skin could coat the surface of the next generation of stealth aircraft.

But the researchers are hoping for even more – a cloak of invisibility.

“The long-term goal is to shrink the size of these devices,” Dong said. “Then hopefully we can do this with higher-frequency electromagnetic waves such as visible or infrared light. While that would require advanced nanomanufacturing technologies and appropriate structural modifications, we think this study proves the concept of frequency tuning and broadening, and multidirectional wave suppression with skin-type metamaterials.”

Nebraska Researcher Find Gold “There’s Gold in them-thare (hills) … rather Nano-Sensors”!


gold-panningInstead of a pan and a pick ax, prospectors of the future might seek gold with a hand-held biosensor that uses a component of DNA to detect traces of the element in water.

The gold sensor is the latest in a series of metal-detecting biosensors under development by Rebecca Lai, an associate professor of chemistry at the University of Nebraska-Lincoln. Other sensors at various stages of development detect mercury, silver or platinum. Similar technology could be used to find cadmium, lead, arsenic, or other metals and metalloids.

A primary purpose for the sensors would be to detect water contaminants, Lai said. She cited the August 2015 blowout of a gold mine near Silverton, Colorado, which spilled chemicals into nearby rivers, as well as the ongoing problems with lead-tainted water supplies in Flint, Michigan.

Gold NEB 021816 rd1602_gold

The photo shows the gold biosensor developed by Rebecca Lai, associate professor of chemistry at the University of Nebraska-Lincoln. The center diagram illustrates how gold ions connect two strands of adenine and hinder electron transmission. The right diagram shows the effect on current signaling the presence of gold. Source: Rebecca Lai/University of Nebraska-Lincoln

Fabricated on paper strips about the size of a litmus strip, Lai’s sensors are designed to be inexpensive, portable and reusable. Instead of sending water samples away for time-consuming tests, people might someday use the biosensors to routinely monitor household water supplies for lead, mercury, arsenic or other dangerous contaminants.

But Lai also is among scientists searching for new and better ways to find gold. Not only aesthetically appealing and financially valuable, the precious metal is in growing demand for pharmaceutical and scientific purposes, including anti-cancer agents and drugs fighting tuberculosis and rheumatoid arthritis.

“Geochemical exploration for gold is becoming increasingly important to the mining industry,” Lai said. “There is a need for developing sensitive, selective and cost-effective analytical methods capable of identifying and quantifying gold in complex biological and environmental samples.”

Scientists have employed several strategies to find gold, such as fluorescence-based sensors, nanomaterials and even a whole cell biosensor that uses transgenic E. coli. Lai was a co-author of a 2013 study that explored the use of E. coli as a gold biosensor.

DNA, the carrier of genetic information in nearly all living organisms, might seem an unlikely method to detect gold and other metals. Lai’s research, however, exploits long-observed interactions between metal ions and the four basic building blocks of DNA: adenine, cytosine, guanine and thymine.

Different metal ions have affinities with the different DNA bases. The gold sensor, for example, is based on gold ions’ interactions with adenine. A mercury sensor is based upon mercury ions’ interaction with thymine. A silver sensor would be based upon silver ions’ interaction with cytosine.

NUtech Ventures, UNL’s affiliate for technology commercialization, is pursuing patent protection and seeking licensing partners for Lai’s metal ion sensors. She applied for a patent for the sensors in 2014.

“Although these interactions have been well-studied, they have not been exploited for use in electrochemical metal ion sensing,” Lai and doctoral student Yao Wu said in a recent Analytical Chemistry article describing the gold sensor.

Lai and Wu say their article is the first report of how oligoadenines — short adenine chains — can be used in the design and fabrication of this class of electrochemical biosensors, which would be able to measure concentrations of a target metal in a water sample as well as its presence.

The DNA-based sensor detects Au(III), a gold ion that originates from the dissolution of metallic gold. The mercury and silver sensors also detect dissolved mercury and silver ions.

“The detected Au(III) has to come from metallic gold, so if gold is found in a water supply, a gold deposit is somewhere nearby,” Lai explained.

The DNA-based biosensors need more refinement before they can be made commercially available, she said.

Lai’s sensor works by measuring electric current passing from an electrode to a tracer molecule, methylene blue in this case. In the absence of Au(III), the observed current is high because the oligoadenine probes are highly flexible and the electron transfer between the electrode and the tracer molecule is efficient.

But upon binding to Au(III) in the sample, the flexibility of the oligoadenine DNA probes is hindered, resulting in a large reduction in the current from the tracer molecule. The extent of the change in current is used to determine the concentration of AU(III) in the sample.

To allow the sensor to be reused multiple times, the Au(III) is later removed from the sensor with an application of another ligand.

Lai’s research focus is on electrochemical ion sensors. Her research has been supported with grants from the National Institutes of Health and the National Science Foundation.

Source: Univ. of Nebraska – Lincoln 

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