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Bio-based communication networks could control cells in the body to treat conditions

Like electronic devices, biological cells send and receive messages, but they communicate through very different mechanisms. Now, scientists report progress on tiny communication networks that overcome this language barrier, allowing electronics to eavesdrop on cells and alter their behavior — and vice versa. These systems could enable applications including a wearable device that could diagnose and treat a bacterial infection or a capsule that could be swallowed to track blood sugar and make insulin when needed.

The researchers will present their results today at the American Chemical Society (ACS) Fall 2020 Virtual Meeting & Expo.

“We want to expand electronic information processing to include biology,” says principal investigator William E. Bentley, Ph.D. “Our goal is to incorporate biological cells in the computational decision-making process.”

The new technology Bentley’s team developed relies on redox mediators, which move electrons around cells. These small molecules carry out cellular activities by accepting or giving up electrons through reduction or oxidation reactions. Because they can also exchange electrons with electrodes, thereby producing a current, redox mediators can bridge the gap between hardware and living tissue. In ongoing work, the team, which includes co-principal investigator Gregory F. Payne, Ph.D., is developing interfaces to enable this information exchange, opening the way for electronic control of cellular behavior, as well as cellular feedback that could operate electronics.

“In one project that we are reporting on at the meeting, we engineered cells to receive electronically generated information and transmit it as molecular cues,” says Eric VanArsdale, a graduate student in Bentley’s lab at the University of Maryland, who is presenting the latest results at the meeting. The cells were designed to detect and respond to hydrogen peroxide. When placed near a charged electrode that generated this redox mediator, the cells produced a corresponding amount of a quorum sensing molecule that bacteria use to signal to each other and modulate behavior by altering gene expression.

In another recent project, the team engineered two types of cells to receive molecular information from the pathogenic bacteria Pseudomonas aeruginosa and convert it into an electronic signal for diagnostic and other applications. One group of cells produced the amino acid tyrosine, and another group made tyrosinase, which converts tyrosine into a molecule called L-DOPA. The cells were engineered so this redox mediator would be produced only if the bacteria released both a quorum sensing molecule and a toxin associated with a virulent stage of P. aeruginosa growth. The size of the resulting current generated by L-DOPA indicated the amount of bacteria and toxin present in a sample. If used in a blood test, the technique could reveal an infection and also gauge its severity. Because this information would be in electronic form, it could be wirelessly transmitted to a doctor’s office and a patient’s cell phone to inform them about the infection, Bentley says. “Ultimately, we could engineer it so that a wearable device would be triggered to give the patient a therapeutic after an infection is detected.”

The researchers envision eventually integrating the communication networks into autonomous systems in the body. For instance, a diabetes patient could swallow a capsule containing cells that monitor blood sugar. The device would store this blood sugar data and periodically send it to a cell phone, which would interpret the data and send back an electronic signal directing other cells in the capsule to make insulin as needed. As a step toward this goal, VanArsdale developed a biological analog of computer memory that uses the natural pigment melanin to store information and direct cellular signaling.

In other work, Bentley’s team and collaborators including Reza Ghodssi, Ph.D., recently designed a system to monitor conditions inside industrial bioreactors that hold thousands of gallons of cell culture for drug production. Currently, manufacturers track oxygen levels, which are vital to cells’ productivity, with a single probe in the side of each vessel. That probe can’t confirm conditions are uniform everywhere in the bioreactor, so the researchers developed “smart marbles” that will circulate throughout the vessel measuring oxygen. The marbles transmit data via Bluetooth to a cell phone that could adjust operating conditions. In the future, these smart marbles could serve as a communication interface to detect chemical signals within a bioreactor, send that information to a computer, and then transmit electronic signals to direct the behavior of engineered cells in the bioreactor. The team is working with instrument makers interested in commercializing the design, which could be adapted for environmental monitoring and other uses.

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Electronic components join forces to take up 10 times less space on computer chips

Electronic filters are essential to the inner workings of our phones and other wireless devices. They eliminate or enhance specific input signals to achieve the desired output signals. They are essential, but take up space on the chips that researchers are on a constant quest to make smaller. A new study demonstrates the successful integration of the individual elements that make up electronic filters onto a single component, significantly reducing the amount of space taken up by the device.

Researchers at the University of Illinois, Urbana-Champaign have ditched the conventional 2D on-chip lumped or distributed filter network design — composed of separate inductors and capacitors — for a single, space-saving 3D rolled membrane that contains both independently designed elements.

The results of the study, led by electrical and computer engineering professor Xiuling Li, are published in the journal Advanced Functional Materials.

“With the success that our team has had on rolled inductors and capacitors, it makes sense to take advantage of the 2D to 3D self-assembly nature of this fabrication process to integrate these different components onto a single self-rolling and space-saving device,” Li said.

In the lab, the team uses a specialized etching and lithography process to pattern 2D circuitry onto very thin membranes. In the circuit, they join the capacitors and inductors together and with ground or signal lines, all in a single plane. The multilayer membrane can then be rolled into a thin tube and placed onto a chip, the researchers said.

“The patterns, or masks, we use to form the circuitry on the 2D membrane layers can be tuned to achieve whatever kind of electrical interactions we need for a particular device,” said graduate student and co-author Mark Kraman. “Experimenting with different filter designs is relatively simple using this technique because we only need to modify that mask structure when we want to make changes.”

The team tested the performance of the rolled components and found that under the current design, the filters were suitable for applications in the 1-10 gigahertz frequency range, the researchers said. While the designs are targeted for use in radio frequency communications systems, the team posits that other frequencies, including in the megahertz range, are also possible based on their ability to achieve high power inductors in past research.

“We worked with several simple filter designs, but theoretically we can make any filter network combination using the same process steps,” said graduate student and lead author Mike Yang. “We took what was already out there to provide a new, easier platform to lump these components together closer than ever.”

“Our way of integrating inductors and capacitors monolithically could bring passive electronic circuit integration to a whole new level,” Li said. “There is practically no limit to the complexity or configuration of circuits that can be made in this manner, all with one mask set.”

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Surface clean-up technology won’t solve ocean plastic problem

Clean-up devices that collect waste from the ocean surface won’t solve the plastic pollution problem, a new study shows.

Researchers compared estimates of current and future plastic waste with the ability of floating clean-up devices to collect it — and found the impact of such devices was “very modest.” However, river barriers could be more effective and — though they have no impact on plastic already in the oceans — they could reduce pollution “significantly” if used in tandem with surface clean-up technology.

The study — by the University of Exeter, the Leibniz Centre for Tropical Marine Research, the Leibniz Institute for Zoo and Wildlife Research, Jacobs University and Making Oceans Plastic Free — focusses on floating plastic, as sunk waste is difficult or impossible to remove depending on size and location.

The authors estimate that the amount of plastic reaching the ocean will peak in 2029, and surface plastic will hit more than 860,000 metric tonnes — more than double the current estimated 399,000 — by 2052 (when previous research suggested the rate of plastic pollution may finally reach zero).

“The important message of this paper is that we can’t keep polluting the oceans and hoping that technology will tidy up the mess,” said Dr Jesse F. Abrams, of the Global Systems Institute and the Institute for Data Science and Artificial Intelligence, both at the University of Exeter.

“Even if we could collect all the plastic in the oceans — which we can’t — it’s really difficult to recycle, especially if plastic fragments have floated for a long time and been degraded or bio-fouled.

“The other major solutions are to bury or burn it — but burying could contaminate the ground and burning leads to extra CO2 emissions to the atmosphere.”

Private initiatives proposing to collect plastic from oceans and rivers have gained widespread attention recently.

One such scheme, called the Ocean Cleanup, aims to clean the “Pacific garbage patch” in the next 20 years using 600m floating barriers to collect plastic for recycling or incineration on land.

The new study analysed the impact of deploying 200 such devices, running without downtime for 130 years — from 2020 to 2150.

In this scenario, global floating plastic debris would be reduced by 44,900 metric tonnes — just over 5% of the estimated global total by the end of that period.

“The projected impact of both single and multiple clean up devices is very modest compared to the amount of plastic that is constantly entering the ocean,” said Dr Sönke Hohn, of Leibniz Centre for Tropical Marine Research.

“These devices are also relatively expensive to make and maintain per unit of plastic removed.”

As most plastic enters the oceans via rivers, the authors say a “complete halt” of such pollution entering the ocean using river barriers — especially in key polluting rivers — could prevent most of the pollution they otherwise predict over the next three decades.

However, due to the importance of large rivers for global shipping, such barriers are unlikely to be installed on a large scale.

Given the difficulty of recycling and the negative impacts of burying or burning plastic, the study says reducing disposal and increasing recycling rates are essential to tackle ocean pollution. “Plastic is an extremely versatile material with a wide range of consumer and industrial applications, but we need to look for more sustainable alternatives and rethink the way we produce, consume and dispose of plastic,” said Professor Agostino Merico, of Leibniz Centre for Tropical Marine Research and Jacobs University.

Dr Roger Spranz, an author of the study, is a co-founder of non-profit organisation Making Oceans Plastic Free.

“We have developed expertise in changing behaviour to break plastic habits and stop plastic pollution at its source,” Dr Spranz said.

“We are registered in Germany but the focus of our activities and collaborations is in Indonesia, the second-largest source of marine plastic pollution.

“Working with local partners, the implementation of our Tasini campaign in Indonesia has to date helped to prevent an estimated 20 million plastic bags and 50,000 plastic bottles from ending up in coastal areas and the ocean.”

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Implantable transmitter provides wireless option for biomedical devices

Purdue University innovators are working on inventions to use micro-chip technology in implantable devices and other wearable products such as smart watches to improve biomedical devices, including those used to monitor people with glaucoma and heart disease.

The Purdue team developed a fully implantable radio-frequency transmitter chip for wireless sensor nodes and biomedical devices. The research is published in the journal IEEE Transactions on Circuits and Systems II. The transmitter chip consumes lowest amount of energy per digital bit published to date.

The transmitter works in a similar fashion to communication technology in mobile phones and smart watches, but the Purdue transmitter has an unprecedented level of miniaturization and low-energy consumption that it can be implanted into an eye to monitor pressure for a glaucoma patient or into another part of the body to measure data related to heart functions.

“A transmitter is an integral part of these kinds of devices,” said Hansraj Bhamra, a research and development scientist who created the technology while he was a graduate student at Purdue. “It facilitates a wireless communication between the sensor node or biomedical device and a smart phone application. The user can simply operate the device through a smart phone application and receive the biophysiological data in real-time. The transmitter in this case enables a 24-hour intraocular pressure monitoring for glaucoma patients”

The Purdue transmitter chip works with sensor nodes in a process similar to the way sensors in the smart cars and other Internet of Things devices connect through various communication components to achieve tasks such as auto-driving.

“In addition to being low power, our transmitter operates on wireless power to replace the conventional batteries,” said Pedro Irazoqui, the Reilly Professor of Biomedical Engineering and professor of electrical and computer engineering at Purdue. “Batteries are undesirable since they increase the device size and weight and make it uncomfortable for patients. In addition, the batteries are built of toxic material and require frequent recharging or replacement surgeries.”

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Novel approach improves graphene-based supercapacitors

Demand for integrated energy storage devices is growing rapidly as people rely more and more on portable and wireless electronics, and the global need grows for clean energy sources such as solar and wind energies.

This is creating an exponential need for advanced energy storage technologies — reliable and maintenance-free batteries and supercapacitors (SC) with high power density capability as storage devices. Supercapacitors are prominent candidates to meet this need due to their environmentally friendly and long cyclability characteristics.

Researchers from the Integrated Nano Systems Lab (INSys Lab), in the Centre for Clean Energy Technology, have been working on a pathway to improve the performance of supercapacitors, and meet that demand for increased storage capacity.

Dr Mojtaba Amjadipour and Professor Francesca Iacopi (School of Data and Electrical Engineering) and Dr Dawei Su (School of Mathematical and Physical Sciences) describe their cutting-edge work in the July 2020 issue of the journal Batteries and Supercaps. The prominence given to Graphitic-Based Solid-State Supercapacitors: Enabling Redox Reaction by In Situ Electrochemical Treatment — designated a Very Important Paper with front coverage placement — signifies just how innovative their research is in developing alternate ways to extend storage capacity.

Dr Iacopi said the multi-disciplinary approach within the team was beneficial in discovering what she says is a simple process.

“This research has originated from our curiosity of exploring the operation limits of the cells, leading us to unforeseen beneficial results. The control of this process would not have been possible without understanding the fundamental reasons for the observed improvement, using our team’s complementary expertise.”

Traditionally, supercapacitors are fabricated with liquid electrolytes, which cannot be miniaturised and can be prone to leakage, prompting research into gel-based and solid-state electrolytes. Tailoring these electrolytes in combination with carbon-based electrode materials such as graphene, graphene oxide, and carbon nanotubes is of paramount importance for an enhanced energy storage performance.

Graphene or graphitic carbon directly fabricated on silicon surfaces offers significant potential for on-chip supercapacitors that can be embedded into integrated systems. The research insights indicate a simple path to significantly enhance the performance of supercapacitors using gel-based electrolytes, which are key to the fabrication of quasi-solid-(gel) supercapacitors.

“This approach offers a new path to develop further miniaturized on-chip energy storage systems, which are compatible with silicon electronics and can support the power demand to operate integrated smart systems,” Dr Iacopi said.

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New printing process advances 3D capabilities

More durable prosthetics and medical devices for patients and stronger parts for airplanes and automobiles are just some of the products that could be created through a new 3D printing technology invented by a UMass Lowell researcher.

Substances such as plastics, metals and wax are used in 3D printers to make products and parts for larger items, as the practice has disrupted the prototyping and manufacturing fields. Products created through the 3D printing of plastics include everything from toys to drones. While the global market for 3D plastics printers is estimated at $4 billion and growing, challenges remain in ensuring the printers create objects that are produced quickly, retain their strength and accurately reflect the shape desired, according to UMass Lowell’s David Kazmer, a plastics engineering professor who led the research project.

Called injection printing, the technology Kazmer pioneered is featured in the academic journal Additive Manufacturing posted online last week.

The invention combines elements of 3D printing and injection molding, a technique through which objects are created by filling mold cavities with molten materials. The marriage of the two processes increases the production rate of 3D printing, while enhancing the strength and properties of the resulting products. The innovation typically produces objects about three times faster than conventional 3D printing, which means jobs that once took about nine hours now only take three, according to Kazmer, who lives in Georgetown.

“The invention greatly improves the quality of the parts produced, making them fully dense with few cracks or voids, so they are much stronger. For technical applications, this is game-changing. The new process is also cost-effective because it can be used in existing 3D printers, with only new software to program the machine needed,” Kazmer said.

The process took about 18 months to develop. Austin Colon of Plymouth, a UMass Lowell Ph.D. candidate in plastics engineering, helped validate the technology alongside Kazmer, who teaches courses in product design, prototyping and process control, among other topics. He has filed for a patent on the new technology.

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The lightest shielding material in the world

Electric motors and electronic devices generate electromagnetic fields that sometimes have to be shielded in order not to affect neighboring electronic components or the transmission of signals. High-frequency electromagnetic fields can only be shielded with conductive shells that are closed on all sides. Often thin metal sheets or metallized foils are used for this purpose. However, for many applications such a shield is too heavy or too poorly adaptable to the given geometry. The ideal solution would be a light, flexible and durable material with extremely high shielding effectiveness.

Aerogels against electromagnetic radiation

A breakthrough in this area has now been achieved by a research team led by Zhihui Zeng and Gustav Nyström. The researchers are using nanofibers of cellulose as the basis for an aerogel, which is a light, highly porous material. Cellulose fibres are obtained from wood and, due to their chemical structure, enable a wide range of chemical modifications. They are therefore a highly popular research object. The crucial factor in the processing and modification of these cellulose nanofibres is to be able to produce certain microstructures in a defined way and to interpret the effects achieved. These relationships between structure and properties are the very field of research of Nyström’s team at Empa.

The researchers have succeeded in producing a composite of cellulose nanofibers and silver nanowires, and thereby created ultra-light fine structures which provide excellent shielding against electromagnetic radiation. The effect of the material is impressive: with a density of only 1.7 milligrams per cubic centimeter, the silver-reinforced cellulose aerogel achieves more than 40 dB shielding in the frequency range of high-resolution radar radiation (8 to 12 GHz) — in other words: Virtually all radiation in this frequency range is intercepted by the material.

Ice crystals control the shape

Not only the correct composition of cellulose and silver wires is decisive for the shielding effect, but also the pore structure of the material. Within the pores, the electromagnetic fields are reflected back and forth and additionally trigger electromagnetic fields in the composite material, which counteract the incident field. To create pores of optimum size and shape, the researchers pour the material into pre-cooled moulds and allow it to freeze out slowly. The growth of the ice crystals creates the optimum pore structure for damping the fields.

With this production method, the damping effect can even be specified in different spatial directions: If the material freezes out in the mould from bottom to top, the electromagnetic damping effect is weaker in the vertical direction. In the horizontal direction — i.e. perpendicular to the freezing direction — the damping effect is optimized. Shielding structures cast in this way are highly flexible: even after being bent back and forth a thousand times, the damping effect is practically the same as with the original material. The desired absorption can even be easily adjusted by adding more or less silver nanowires to the composite, as well as by the porosity of the cast aerogel and the thickness of the cast layer.

The lightest electromagnetic shield in the world

In another experiment, the researchers removed the silver nanowires from the composite material and connected their cellulose nanofibres with two-dimensional nanoplates of titanium carbide, which were produced using a special etching process. The nanoplates act like hard “bricks” that are joined together with flexible “mortar” made of cellulose fibers. This formulation was also frozen in cooled forms in a targeted manner. In relation to the weight of the material, no other material can achieve such shielding. This ranks the titanium carbide nanocellulose aerogel as by far the lightest electromagnetic shielding material in the world.

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Nanodevices show how cells change with time, by tracking from the inside

For the first time, scientists have introduced minuscule tracking devices directly into the interior of mammalian cells, giving an unprecedented peek into the processes that govern the beginning of development.

This work on one-cell embryos is set to shift our understanding of the mechanisms that underpin cellular behaviour in general, and may ultimately provide insights into what goes wrong in ageing and disease.

The research, led by Professor Tony Perry from the Department of Biology and Biochemistry at the University of Bath, involved injecting a silicon-based nanodevice together with sperm into the egg cell of a mouse. The result was a healthy, fertilised egg containing a tracking device.

The tiny devices are a little like spiders, complete with eight highly flexible ‘legs’. The legs measure the ‘pulling and pushing’ forces exerted in the cell interior to a very high level of precision, thereby revealing the cellular forces at play and showing how intracellular matter rearranged itself over time.

The nanodevices are incredibly thin — similar to some of the cell’s structural components, and measuring 22 nanometres, making them approximately 100,000 times thinner than a pound coin. This means they have the flexibility to register the movement of the cell’s cytoplasm as the one-cell embryo embarks on its voyage towards becoming a two-cell embryo.

“This is the first glimpse of the physics of any cell on this scale from within,” said Professor Perry. “It’s the first time anyone has seen from the inside how cell material moves around and organises itself.”

WHY PROBE A CELL’S MECHANICAL BEHAVIOUR?

The activity within a cell determines how that cell functions, explains Professor Perry. “The behaviour of intracellular matter is probably as influential to cell behaviour as gene expression,” he said. Until now, however, this complex dance of cellular material has remained largely unstudied. As a result, scientists have been able to identify the elements that make up a cell, but not how the cell interior behaves as a whole.

“From studies in biology and embryology, we know about certain molecules and cellular phenomena, and we have woven this information into a reductionist narrative of how things work, but now this narrative is changing,” said Professor Perry. The narrative was written largely by biologists, who brought with them the questions and tools of biology. What was missing was physics. Physics asks about the forces driving a cell’s behaviour, and provides a top-down approach to finding the answer.

“We can now look at the cell as a whole, not just the nuts and bolts that make it.”

Mouse embryos were chosen for the study because of their relatively large size (they measure 100 microns, or 100-millionths of a metre, in diameter, compared to a regular cell which is only 10 microns [10-millionths of a metre] in diameter). This meant that inside each embryo, there was space for a tracking device.

The researchers made their measurements by examining video recordings taken through a microscope as the embryo developed. “Sometimes the devices were pitched and twisted by forces that were even greater than those inside muscle cells,” said Professor Perry. “At other times, the devices moved very little, showing the cell interior had become calm. There was nothing random about these processes — from the moment you have a one-cell embryo, everything is done in a predictable way. The physics is programmed.”

The results add to an emerging picture of biology that suggests material inside a living cell is not static, but instead changes its properties in a pre-ordained way as the cell performs its function or responds to the environment. The work may one day have implications for our understanding of how cells age or stop working as they should, which is what happens in disease.

The study is published this week in Nature Materials and involved a trans-disciplinary partnership between biologists, materials scientists and physicists based in the UK, Spain and the USA.

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Microbial cyborgs: Bacteria supplying power

Electronic devices are still made of lifeless materials. One day, however, “microbial cyborgs” might be used in fuel cells, biosensors, or bioreactors. Scientists of Karlsruhe Institute of Technology (KIT) have created the necessary prerequisite by developing a programmable, biohybrid system consisting of a nanocomposite and the Shewanella oneidensis bacterium that produces electrons. The material serves as a scaffold for the bacteria and, at the same time, conducts the microbially produced current. The findings are reported in ACS Applied Materials & Interfaces.

The bacterium Shewanella oneidensis belongs to the so-called exoelectrogenic bacteria. These bacteria can produce electrons in the metabolic process and transport them to the cell’s exterior. However, use of this type of electricity has always been limited by the restricted interaction of organisms and electrode. Contrary to conventional batteries, the material of this “organic battery” does not only have to conduct electrons to an electrode, but also to optimally connect as many bacteria as possible to this electrode. So far, conductive materials in which bacteria can be embedded have been inefficient or it has been impossible to control the electric current.

The team of Professor Christof M. Niemeyer has now succeeded in developing a nanocomposite that supports the growth of exoelectrogenic bacteria and, at the same time, conducts current in a controlled way. “We produced a porous hydrogel that consists of carbon nanotubes and silica nanoparticles interwoven by DNA strands,” Niemeyer says. Then, the group added the bacterium Shewanella oneidensis and a liquid nutrient medium to the scaffold. And this combination of materials and microbes worked. “Cultivation of Shewanella oneidensis in conductive materials demonstrates that exoelectrogenic bacteria settle on the scaffold, while other bacteria, such as Escherichia coli, remain on the surface of the matrix,” microbiologist Professor Johannes Gescher explains. In addition, the team proved that electron flow increased with an increasing number of bacterial cells settling on the conductive, synthetic matrix. This biohybrid composite remained stable for several days and exhibited electrochemical activity, which confirms that the composite can efficiently conduct electrons produced by the bacteria to an electrode.

Such a system does not only have to be conductive, it also must be able to control the process. This was achieved in the experiment: To switch off the current, the researchers added an enzyme that cuts the DNA strands, as a result of which the composite is decomposed.

“As far as we know, such a complex, functional biohybrid material has now been described for the first time. Altogether, our results suggest that potential applications of such materials might even extend beyond microbial biosensors, bioreactors, and fuel cell systems,” Niemeyer emphasizes.

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Scientists break the link between a quantum material’s spin and orbital states

In designing electronic devices, scientists look for ways to manipulate and control three basic properties of electrons: their charge; their spin states, which give rise to magnetism; and the shapes of the fuzzy clouds they form around the nuclei of atoms, which are known as orbitals.

Until now, electron spins and orbitals were thought to go hand in hand in a class of materials that’s the cornerstone of modern information technology; you couldn’t quickly change one without changing the other. But a study at the Department of Energy’s SLAC National Accelerator Laboratory shows that a pulse of laser light can dramatically change the spin state of one important class of materials while leaving its orbital state intact.

The results suggest a new path for making a future generation of logic and memory devices based on “orbitronics,” said Lingjia Shen, a SLAC research associate and one of the lead researchers for the study.

“What we’re seeing in this system is the complete opposite of what people have seen in the past,” Shen said. “It raises the possibility that we could control a material’s spin and orbital states separately, and use variations in the shapes of orbitals as the 0s and 1s needed to make computations and store information in computer memories.”

The international research team, led by Joshua Turner, a SLAC staff scientist and investigator with the Stanford Institute for Materials and Energy Science (SIMES), reported their results this week in Physical Review B Rapid Communications.

An intriguing, complex material

The material the team studied was a manganese oxide-based quantum material known as NSMO, which comes in extremely thin crystalline layers. It’s been around for three decades and is used in devices where information is stored by using a magnetic field to switch from one electron spin state to another, a method known as spintronics. NSMO is also considered a promising candidate for making future computers and memory storage devices based on skyrmions, tiny particle-like vortexes created by the magnetic fields of spinning electrons.

But this material is also very complex, said Yoshinori Tokura, director of the RIKEN Center for Emergent Matter Science in Japan, who was also involved in the study.

“Unlike semiconductors and other familiar materials, NSMO is a quantum material whose electrons behave in a cooperative, or correlated, manner, rather than independently as they usually do,” he said. “This makes it hard to control one aspect of the electrons’ behavior without affecting all the others.”

One common way to investigate this type of material is to hit it with laser light to see how its electronic states respond to an injection of energy. That’s what the research team did here. They observed the material’s response with X-ray laser pulses from SLAC’s Linac Coherent Light Source (LCLS).

One melts, the other doesn’t

What they expected to see was that orderly patterns of electron spins and orbitals in the material would be thrown into total disarray, or “melted,” as they absorbed pulses of near-infrared laser light.

But to their surprise, only the spin patterns melted, while the orbital patterns stayed intact, Turner said. The normal coupling between the spin and orbital states had been completely broken, he said, which is a challenging thing to do in this type of correlated material and had not been observed before.

Tokura said, “Usually only a tiny application of photoexcitation destroys everything. Here, they were able to keep the electron state that is most important for future devices — the orbital state — undamaged. This is a nice new addition to the science of orbitronics and correlated electrons.”

Much as electron spin states are switched in spintronics, electron orbital states could be switched to provide a similar function. These orbitronic devices could, in theory, operate 10,000 faster than spintronic devices, Shen said.

Switching between two orbital states could be made possible by using short bursts of terahertz radiation, rather than the magnetic fields used today, he said: “Combining the two could achieve much better device performance for future applications.” The team is working on ways to do that.

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