The Kynix Blog

SummaryMemory is one of the most important part for electronics. Computers and Smartphones woludn't be nearly as useful without room for lots of apps,music and videos. Devices tend to store that  information in two ways: through electric fields (think of a flash drive) or through magnetic fields (like a computer’s spinning hard disk). Each method has advantages and disadvantages. However, in the future, our electronics could benefit from the best of each. There are some questions put by Chang-Beom Eom, the Theodore H. Geballe Professor and Harvey D. Spangler Distinguished Professor of Materials Science and Engineering at the University of Wisconsin-Madison. “Can you cross-couple these two different ways to store information? Could we use an electric field to change the magnetic properties? Then you can have a low-power, multifunctional device. We call this a ‘magnetoelectric’ device.” In research published recently in the journal Nature Communications, Eom and his collaborators describe not only their unique process for making a high-quality magnetoelectric material, but exactly how and why it works. Physics graduate student Julian Irwin checks equipment in the lab of materials science and engineering Professor Chang-Beom Eom, where researchers have produced a material that could exhibit the best qualities of both solid-state and spinning disk digital storage. Magnetoeletric materialsMagnetoelectric materials,which have both magnetic and electrical functionalities,or "orders" already exist. Switching one functionality induces a change in the other.“It’s called cross-coupling,” says Eom. “Yet, how they cross-couple is not clearly understood.” Gaining that understanding, he says, requires studying how the magnetic properties change when an electric field is applied. Up to now, this has been difficult due to the complicated structure of most magnetoelectric materials. In the past,people studied magnetoelectric properties using very "complex" materials,or those that lack uniformity.In his approach,Eom simplified not only the research but the material itself. Drawing on Eom's expertise in material growth,he developed a unique process,using atomic "steps" to guide the growth of a homogenous,single-crystal thin film of bismuth ferrite. Atop that, he added cobalt, which is magnetic; on the bottom, he placed an electrode made of strontium ruthenate.  Bismuth Ferrite MaterialThe bismuth ferrite material was important because it made it much easier for Eom to study the fundamental magnetoelectric cross-coupling. Eom found that in their work,because of their single domain,they could actually see what was going on using multiple probing, or imaging, techniques.The mechanism is intrinsic. It’s reproducible — and that means you can make a device without any degradation, in a predictable way. To image the changing  electric and magnetic properties switching in real time, Eom and his colleagues used the powerful synchrotron light sources at Argonne National Laboratory outside Chicago, and in Switzerland and the United Kingdom. “When you switch it, the electrical field switches the electric polarization. If it’s ‘downward,’ it switches ‘upward,'” he says. “The coupling to the magnetic layer then changes its properties: a magnetoelectric storage device.” That change in direction enables researchers to take the next steps needed to add programmable integrated circuits — the building blocks that are the foundation of our electronics — to the material. While the homogenous material enabled Eom to answer important scientific questions about how magnetoelectric cross-coupling happens, it also could enable manufacturers to improve their electronics.Eom saied they can design a much more effective,efficient and low-power device now. 

SummaryRS-485 has been an industrial workhorse because of its robustness and reliability.  Initially used as a communication network in laboratory instrumentation, RS-485 can be found in applications ranging from building automation to traffic monitoring systems. As the use of RS-485 grew, demand increased for a higher output voltage swing, a wider common-mode range and increased tolerance to electrostatic discharges. There was also a need for greater stand-off capability or protection against persistent over-voltages beyond the maximum transceiver supply level specified in datasheets.  OVP Versus Transient Protection  As the above picture shows,the 24V and 48V DC supplies in industrial and telecom systems are commonly distributed through the same conduits as the data lines of an RS-485 network,there can be multiple causes for over-voltage faults when data lines share the same conduits as DC power lines. On the one hand,if a DC supply shares the same connector or screw terminal block with the data lines of an adjacent bus node circuit,wiring faults can occur that connect one or more supply conductors with the transceiver bus terminals. Another cause of failures is the layouto of the conduit. Sharp bends often violate the minimum cable radius specified for data and supply cables. Over time, the increased mechanical pressure on the cable will cause a break in the insulation, causing shorts between power and data lines. This can also happen when machinery or equipment is placed against a conduit, thus crunching the cable. Over-voltage events can last for minutes and even up to weeks until their causes are eliminated. Much shorter over-voltage events, such as over-voltage transients, can occur due to load switching activity in the power distribution system and lightning strikes, which induce high surge currents and voltages into the data lines. Engineers new to over-voltage protection often assume that protection against short- and long-term over-voltages can be provided by adding external transient voltage suppressors (TVS) to a non-fault protected, standard transceiver. This is not true because the maximum power which the TVS can absorb decreases with increasing transient duration. The following image shows a 600W TVS rated at 1ms pulse width. Note that the time axis ranges from 10μs to 10ms, with power levels of 6kW and 200W respectively. From this characteristic, it should be clear that exposing a TVS to long-term over-voltages would fry the device.  Therefore fault protected transceivers are needed to protect bus nodes against a wide range of over-voltages. These transceivers can provide protection against DC over-voltages of up to ±60V and transient over-voltages of up to ±80V.   Integrated Versus DiscreteOccasionally, designers ask ‘why not use a non-fault protected, standard transceiver and a few discrete low-cost transistors with sufficient high voltage breakdown for over-voltage protection?’. The answer is simple: A discrete solution adds more cost and development time and consumes more space than a fault-protected transceiver. Let's assume the function of the fault-protected, half-duplex transceiver in the following picture is to be accomplished with a discrete design using a standard transceiver. First, the transmit path and the receive path must be separate to allow for the implementation of a boosted output stage with high standoff voltage. This requires the use of a full duplex transceiver. The output stage could be realised with four discrete transistors or an integrated H-bridge, whose control inputs require the conversion of RS-485 bus signals into TTL or CMOS logic levels. This would require a drive logic circuit between the transceiver and the discrete output stage. In the receive path, a discrete voltage limiter, consisting of Zener diodes and series resistors, must be implemented to limit the bus voltage during an over-voltage event, otherwise it remains transparent. The following picture shows that the discrete solution already becomes cumbersome by merely providing the basic functions for over-voltage protection, while still lacking a current limiter, which is a vital component for over-voltage protection. Current limiting is a critical function during over-voltage events when the driver is actively driving the bus. Because the enabled driver presents a low-impedance connection to ground, bus currents flowing through the driver become huge, damaging the device if they are not limited. Current LimitingFault-protected transceivers with common-mode ranges wider than specified in the RS-485 standard require double fold-back current limiting within the driver stage. Figure 4 shows the current limiting function of the ISL3245x family of fault-protected transceivers that operate over the wide common-mode range of ±20V. Here, the first fold-back current level of 63mA ensures that the driver never folds back when driving loads within the entire 40V common-mode voltages. The low second fold-back current setting of 13mA minimises power dissipation if the driver is enabled when a fault occurs. This current limiting scheme ensures that the output current never exceeds the RS-485 specification, even at the common mode and fault condition voltage range extremes. In the event of a major short-circuit condition, the transceivers also provide a thermal shutdown function that disables the drivers whenever the die temperature becomes excessive. This eliminates any power dissipation and allows the die to cool. The drivers automatically re-enable after the die temperature drops by 15°C. If the fault condition persists, the thermal shutdown/re-enable cycle repeats until the fault is cleared. Receivers stay operational during thermal shutdown and fault-protection is active, regardless of whether the driver is enabled, disabled or the IC is powered down.The energy of over-voltage transients caused by lightning can easily exceed the transceiver's fault protection and must be absorbed by external TVS diodes. Two conditions need to be satisfied when adding external TVS devices to a fault-protected transceiver: The TVS breakdown voltage must be 1V higher than the highest common-mode voltage of the application or the maximum DC-supply, whichever is higher.The peak clamping voltage of the TVS must be less than the transceiver’s maximum fault-protection levels.Fault-protected transceivers with a wide supply voltage range enable designers to use the same device in 3.3 and 5V systems, which reduces logistics and can lead to an attractive price break for higher volumes. However, not all 3V to 5V transceivers provide sufficient drive capability at low supply and neither do they necessarily operate down to 3V. ClosingSystem designers are no longer required to choose between robust fault tolerance and high performance in RS-485 and RS-422 transceivers; devices such as the ISL32458E and ISL32459E from Intersil offer both. These transceivers feature ±60V over-voltage and ±15kV ESD tolerance, while including operation from supply voltages ranging from 3V to 5.5V. They also operate with data rates of up to 20Mbit/s and provide a ±20V common-mode voltage range. In addition the ISL32459E provides a cable-invert function.  Article resources: Writed by Thomas Kugelstadt,a principal applications engineer with Intersil, a Renesas companyArticle edited by kynix 

SummarySingaporean researchers,led by by professor Hirotaka Sato,describe their work about designing robots--It's possible to use a living insect as a platform to develop a living insect-machine hybrid robot.Such a hybrid retains the complex structure of the insect's rigid exokeleton,complaint joints,and soft actuators, as well as the insect’s locomotion capability, and it does so while enabling high controllability and low power consumption. Such an insect-machine hybrid robot is made of a living insect platform with a miniaturized electronic device attached on it to control it.   By using the insect itself as the robot, researchers bypass the complex processes of designing and fabricating the robot body, using the insect’s muscular system as the soft actuators and flexible joints and its nervous system as part of the control system. About BeetleThis kind of particular beetle is a a darkling beetle. It’s small (2 to 2.5 centimeters), lightweight (about 0.5 gram), and lives for three months or so, which is a long time for a little bug. A backpack of electronics interfaces with the beetle’s antennae, and when the antennae are stimulated with an electric pulse, it activates the beetle’s built-in escape mechanism, fooling it into thinking it’s running into something and causing it to turn. The picture is from Nanyang Technological University AdvantageThe advantage of doing things this way (as opposed to direct nerve or muscle stimulation, something that the researchers also experimented with) is that the beetle’s brain is still in charge of controlling its limbs such that it’ll respond to high-level controls with adaptive gaits and such, making locomotion a much simpler problem to solve. With just two coin cell batteries, the cybeetle can be controlled for 8 hours, which is long enough for it to travel over a kilometer at an average speed of 4 cm/s. The following picture is from  Cyborg Insect: Ultralightweight Living Legged Robot The key to effectively controlling an insect using these methods is that the response to the antenna stimulation can’t be binary, since you’d end up with a level of control that would often be too coarse to be useful. By changing the frequency of the stimulation, the researchers were able to modulate how sharp of a turn the insect took: Increasing the stimulation frequency also increased the insect’s turning rate, with a success rate of over 85 percent. Stimulating both antennae at once causes the insect to back up, and it moves forward by default, giving you just about as much control as you can hope for. Living Robots' DifferencesElectrical stimulation is commonly used for neuromuscular stimulation in cyborg insects such as cockroaches, giant beetles, and moths. There are other groups working on antenna stimulation but they were not able to grade the response of the insect, which is very important for developing a precise closed-loop control system to make the cyborg insect work autonomously. The giant cyborg beetle mainly relies on neuromuscular stimulation of direct flight muscles for flight control and leg muscles of the fore legs for walking control. Ideally, stimulating the muscle would be more precise as we can perfectly control the individual legs, but it costs more in implantation and computing to plan and stimulate all the individual muscles for walking. Antenna stimulation is simpler and easier than stimulating all the individual muscles thus it helps us to simplify the hardware and control system a lot. Hopefully, in the near future, we can control the cyborg beetle as precisely as any other artificial motor. The zophobas beetle were used to develop this cyborg insect because its small size (2-2.5 cm) would help it to access the small rubbles system easily at disaster sites, where the cockroach and giant beetle can not get in. Moreover, a swarming of flying and walking cyborg insects of various sizes would increase the coverage and reduce the searching time, thus enhancing the efficiency and accuracy of search and rescue operations. Control IssueFor walking cyborg insects, researchers are able to integrate external sensors into the backpack as the insect is able to carry loads up to double its weight. We are developing a new backpack with integrated sensors for human detection and navigation. It would help us to detect victims when using cyborg insects at disaster sites, and enable the cyborg insects to work autonomously. On the other hand,research could release hundreds of flying and crawling cyborg insects to the sites as the price for one cyborg insect would be negligible once mass produced for a disaster scenario.The insects can move freely themselves into the collapsed structures and send back maps of their positions and environmental conditions so that the rescue team can plan for their action efficiently on how and where they should access. Once an insect detects a victim, it will send an alarm to the rescue team and switch to autonomous control mode to move around the victim for confirmation and build a clearer map of surrounding environment. At the end of the rescue operation, all the insects will autonomously return to the control base. I know that it sounds like science fiction, but we are in fact working to realize it. Researcher's GoalNow,researchers are working on a feedback control system to precisely control the insect locomotion with high reliability. We are also developing a new backpack with a navigation system and environmental sensors designed to promote fully autonomous and practical cyborg insects. For real applications, we need to maintain the power supply for the cyborg insect (mainly for the electronics backpack), which is currently a huge challenge if we just rely on the battery. So we are developing a biofuel cell, which is able to convert biofuel inside the insect to electric current for running the control backpack. It will help to maintain the backpack power for long-term use. Article resources: journal Soft RoboticsAtticle edited by kynix 

SummaryIn the development of advanced lithium-ion battery,improving one property without sacrificing others is challenging due to the trade-off nature among the key parameters. In a recent paper in Nature Communications, a research team from the Samsung Advanced Institute of Technology reported a chemical vapor deposition process to grow a graphene-silica 3D assembly, called a graphene-ball to provide both fast charging and high volumetric energy densities in Li-ion batteries.  About GrapheneIts hierarchical 3D structure with the SiOx nanoparticle center allows even 1 wt％ graphene-ball to be uniformly coated onto a nickel-rich layered cathode (LiNi0.6Co0.1Mn0.3O2) via mild Nobilta milling. The graphene-ball coating improves cycle life and fast charging capability by protecting the electrode surface from detrimental side reactions and providing efficient conductive pathways. The graphene-ball itself also serves as an anode material with high specific capacity of 716.2 mAh g-1. A full-cell incorporating graphene-balls increases the volumetric energy density by 27.6％ compared to a control cell without graphene-balls, showing the possibility of achieving 800 Wh L-1 in a commercial cell setting, along with a high cyclability of 78.6％ retention of the initial capacity after 500 cycles at 5C and 60 degrees C. Graphene growth from SiO2 nanoparticles. a-c TEM characterization a before CVD growth, b after 5 min growth, and c after 30 min growth (scale bars, 50 nm). d-f Their respective magnified images (scale bars, 10 nm). g Higher magnification image of graphene after 30 min growth and its atom-level view from the white box (inset) (scale bar, 2 nm). h Graphical illustration of popcorn-like graphene growth from SiO2 nanoparticles. A Boom in the Creation of New DevicesRecent innovations in materials science such as the development of graphene balls for Li-ion batteries have led to a boom in the creation of new devices, allowing for a rapid shift from analog to digital in a relatively short amount of time.In the past, materials were researched, developed and perfected long before they were applied to devices. Take liquid crystals, for example. They were first discovered in the late 1800s, and for decades were studied and defined in the academic realm. It wasn't until the 1960s―almost a century later―that they were utilized in commercial products. Similarly, it took 30 years after its invention for lithium metal oxide to even be tested in batteries, and another decade before it made its official commercial market introduction. Once materials such as these were introduced, however, they allowed for a steady and fairly rapid increase in device performance. In the display industry specifically, there has been enormous growth in the market because of such advancements up until now.However, as the market becomes increasingly saturated, electronic materials innovations are beginning to fall behind the device revolution. This is mostly due to the fact that the device product life cycle is becoming much faster than that of the material. Now, the device itself is facing the limitations of this revolution in terms of product performance and functionality without the aid of novel materials. Research on Materials and DevicesIt's reported at the  the plenary session led by Dr. Hyuk Chang, Executive Vice President , Samsung Advanced Institute of Technology (SAIT), at the 9th International Conference on Quantum Dots held that to ensure consistent advancements and optimum functionality, both materials and devices have to be synchronized throughout the development process from the earliest stages of research so that performance requirements can be properly understood. The following picture is about the speeds of material and device innovation have changed over time. SAIT now aims to synchronize the two. Chang noted that the synchronization of materials research and device development can accelerate the enhancement of both the devices and the materials that they are made of, thus revitalizing the market."After all, innovation comes in many forms, and source technology is a foundational one," Chang said. At Samsung, there are numerous organizations that carry out research and development. These include SAIT, where the company pioneers long-term, radical researches with five to ten year or more horizons; the R&D centers that explore next-generation products and platform technologies one to three years in advance; and business unit development teams that focus on commercialization, applying these latest technologies in product development.Samsung is increasingly synchronizing its R&D efforts to bring core technologies like new materials to products more quickly.Take an example,the quantum dot technology.Confident that this specific technology could ultimately drive the future of display, among other areas, Samsung has researched the material and its advantages in earnest. In fact, researchers at SAIT started focusing on quantum dot technology over a decade ago, and have since registered numerous patents on the subject. The following picture is about a synchronized research roadmap Through constant testing, evaluating and verifying the material from the earliest stages of device design, Samsung was able to incorporate quantum dots to create a revolutionary line-up of products―its 2015 SUHD TVs. n doing so, the technology allowed for highly accurate color expression and better, brighter picture quality while improving overall energy efficiency at a lower cost―all with cadmium-free quantum dots. Considering that this was the first commercial application of the material, it created quite a buzz among academics in the field who had been eagerly anticipating such a milestone. Despite these accomplishments, Samsung wanted to improve upon this technology and did so with its 2016 SUHD TVs, making them even more energy-efficient, and allowing them to display the picture quality more accurately. "As a materials scientist, my previous work was in small-scale labs," Chang explained. "It was overwhelming to see this technology make its way to mass production and even hit center stage at the industry's top events like CES in just a decade. That's the speed and scale of Samsung."As Samsung continues to research and refine the technology, the company predicts that quantum dots will further enhance display devices.Chang noted that quantum dots could be applied in other ways, too, such as to improve the accuracy of image sensors, which could significantly advance autonomous cars. Experts note that the technology also has great potential in the areas of chemo- and bio-sensing. In fact, researchers at SAIT have already begun to utilize quantum dot technology in these areas, and are eager to continue to progress these developments. "Just as Samsung's SUHD TVs were realized by evolutionary quantum dot materials and boundless research for discovering novel physical phenomena, functional materials, value-added materials and next-generation devices must be closely interconnected," Chang stated. This, he believes, will accelerate materials innovations, leading to new functionalities in devices and the creation of novel devices. The synchronization of materials research and device development will also help to breathe new life into the massive global materials marketplace. By consistently providing added value with new materials, Samsung hopes to continue to revitalize the electronic devices industry. Article resources:Samsung Advanced Institute of TechnologyArticle edited: kynix 

SummaryIt has been successfully demonstrated that a nanocrystal of of perovskite can serve as a quantum emitter of light, and, when coupled with a nanophotonic cavity, can dramatically improve the efficiency of the light emission by an international research team from the University of Maryland and ETH Zurich in Switzerland.  A new device features perovskite nanocrystals and a series of nanophotonic cavities. The arrows indicate the way that the UV laser used to excite the crystals, and the light  the crystals produce, move in and out of the device. Described in the Journal Applied Physics Letters ,the resulting device and method could be used to build nanolasers and optical devices that exhibit much faster response times than currently possible. Previously, there have been other quantum emitting materials that have been coupled to nanophotonic cavities. In this area, epitaxial materials such as quantum dots have garnered the most research interest. Distinct advantage to using PerovskiteHowever, the researchers believe there are some distinct advantages to using perovskite nanocrystals instead of epitaxial materials, which involve the fairly complex deposition of a crystalline layer on a crystalline substrate.Instead of the epitaxial techniques, the perovskite nanocrystals are synthesized using inexpensive colloidal chemistry techniques. This also makes it possible for these crystals to be placed on a broad range of substrates using simpler solution-deposition techniques when they are coupled to various photonic structures. The other main set of advantages for perovskites in light-emitting applications relates back to why they have become such a darling in photovoltaics: their optical and electrical properties. Perovskites exhibit a slow non-radiative decay rate and low densities of carrier-trapping defects, which contributes to their high photoluminescence efficiency at room temperature.In addition, the emission spectrum could cover the whole visible range by controlling the size and material composition, especially for the blue-green wavelengths that are otherwise difficult to access. The device operates by exciting the coupled system using a UV laser. This excites the perovskites to a higher energy level. Within a nanosecond, the exciton (an excited electron-hole pair) will decay to its ground state while transforming its energy in the form of an emitting photon. The cavity introduces more decay channels to the emitting materials, so a majority of the photons are coupled into the cavity and form the standing mode of the cavity. Finally, the researchers are able to detect the photons leaking away from the cavity, which is the emission signal. Difficult metThe problem that previous attempts have encountered in working with nanocrystal perovskites has been the material quality. “We need emitters with good photostability, so it can hold the performance when coupling to the cavities, said Yang. “Our collaborators from ETH provided perovskites that make this coupling possible.” In addition to nanolasers and faster optoelectronics, Yang believes the device they have made could increase the efficiency of existing perovskite emitting devices, such as LEDs, which could open up real-world applications in efficient illumination and displays. Before these aspirations can be realized, Yang concedes that they will need to further improve the performance and stability of the material itself. Second, it would be better to excite the material electrically rather than optically for practical use.Yang will try to realize similar devices spanning the whole visible range and the next step it to find ways to further improve and stabilize the performance and also utilizing electrical gates to excite the material in devices. Article source: Applied Physics LettersArticle edited by kynix 

SummaryWe know that empty batteries are easy to recognize.However,it is much more complicated to know the charge status between full and empty.A complete new approach with ultrasound pluses offers a precise and simple method. Batteries are used in many "mobile" technologies,and that is why it is the snag in "mobile" technologies. Like smartphones,drones,or electric cars-in many cases he time between battery charges is much too short for many people. This is why it is important to determine the exact state of charge. But this is more complicated than you would imagine. Currently, battery management systems (BMS) carry out the necessary measurements. They calculate the state of charge for each cell based on the parameters current and voltage.  However, since the calculations are partly based on standard values, they reflect the current state only approximately. In particular, this is very inaccurate in case of frequent partial charges. The battery management systems also consume some of the energy that was actually to be used for the next song or mile. About the aboving picture:Sensors with 1 cm and 2 cm diameter to measure the state of charge of the battery Battery Management with UltrasoudIn the future this will be more reliable, more energy saving and cheaper with sensor systems that are being developed in the SoCUS project at the Fraunhofer ISC. They measure the density of the negative anode with the help of ultrasound pulses. This changes as the state of charge of the cell changes.The method has several advantages: there is a direct linear connection between the state of charge and the measurement signal. This makes the evaluation simpler and more precise than with the technologies currently in use.The new battery sensors can be easily integrated into existing systems.One evaluation unit can monitor several battery cells simultaneously and measures the state of charge only during charging and discharging. The fact that this system does not check the charge continuously saves energy and, consequently, costs.Since the ultrasound signal correlates directly with the mechanical properties of the cell, all aging processes are taken into account better. This allows more accurate statements to be made about the current remaining capacity and, hence, the performance.  About the above picture: Principle of the state-of-charge estimation by ultrasonic pulsed excitations: A RCN-pulse transmitted through the cell gives rise to two wave packets (wave I and II), where the slower (wave II) ones' amplitude shows a linear relationship on the state-of-charge. For optimized signal strength of-the-shelf piezo transducers are attached centered on opposite sides of commercial pouch-type cells. Battery Management with All TypesThe new measuring method is suitable for almost all types of battery. However, to date only lithium ion batteries have been tested. In particular, electric vehicles should benefit from reliable recording of the battery charge status. After all, the distance covered between charges is the key factor for further development. But reliable monitoring of the state of charge is also important for drones that monitor industrial plants and wind parks or that manage agricultural land. The ultrasound method could be especially profitable for stationary storage systems with a large number of connected battery cells. A sensor that works only when required and records the state of charge of several cells simultaneously can save energy and also costs. In this application, flame retardant battery types are often used where the state of charge cannot be determined accurately with current methods. The new method could extend existing measurement methods of battery management systems in the future, especially also in electric mobility with a reliable, energy-saving, inexpensive variant.