Science category

Thin, flexible cooling device

Researchers Developed New Efficient, Thin, and Flexible Cooling Device

Engineers and scientists from the UCLA Henry Samueli School of Engineering and Applied Science and SRI International, California, have created a thin flexible device that could keep smartphones and laptop computers cool and prevent overheating. The component is based on the electrocaloric effect – a phenomenon where the temperature of material changes when an electric field is applied to it. The research has been published in Science.

Thin, flexible cooling device
Thin, flexible cooling device

The system’s flexibility also allows it to be used in wearable electronics, robotic systems, and new types of personalized cooling systems. It is the first demonstration of a solid-state cooling device based on the electrocaloric effect. The method devised by UCLA and SRI researchers is very energy-efficient. It uses a thin polymer film that transfers heat from the heat source – a battery or a processor – to a heat sink, and alternates contact between the two by switching on and off the electric voltage.

Because the polymer film is very flexible, the system can be used in devices with complex shapes or moving surfaces. Body tracking wearable devices can easily accommodate this flexible cooling device. Such cooling pad could keep a person comfortable in a hot office and thus lower the electricity consumption for air conditioning. Or it could be placed in a shoe to keep a runner comfortable while running in the sun. It’s like a personal air conditioner.

The tendency of flexible electronics to overheat remains a major challenge for engineers. The cooling systems in larger devices like air conditioners and refrigerators, which use vapor compression, are just too large for mobile electronics. The new cooling device produces a specific cooling power of 2.8 watts per gram and a COP of 13. This is more efficient and compact than the existing surface-mountable solid-state cooling technologies, opening a path to using the technology for a variety of practical applications.

Roy Kornbluh, an SRI research engineer, said,

The development of practical efficient cooling systems that do not use chemical coolants that are potent greenhouse gases is becoming even more important as developing nations increase their use of air conditioning.

loihi - Intel's self-learning chip

Intel Introduces Loihi – A Self Learning Processor That Mimics Brain Functions

Intel has developed a first-of-its-kind self-learning neuromorphic chip – codenamed Loihi. It mimics the animal brain functions by learning to operate based on various modes of feedback from the environment. Unlike convolutional neural network (CNN) and other deep learning processors, Intel’s Loihi uses an asynchronous spiking model to mimic neuron and synapse behavior in a much closer analog to animal brain behavior.

loihi - Intel's self-learning chip
Loihi – Intel’s self-learning chip

Machine learning models based on CNN use large training sets to set up recognition of objects and events. This extremely energy-efficient chip, which uses the data to learn and make inferences, gets smarter over time and does not need to be trained in the traditional way. The Loihi chip includes digital circuits that mimic the brain’s basic mechanics, making machine learning faster and more efficient while requiring much lower computing power.

The chip offers highly flexible on-chip learning and combines training and inference on a single chip. This allows machines to be autonomous and to adapt in real time instead of waiting for the next update from the cloud. Compared to convolutional neural networks and deep learning neural networks, the Loihi test chip uses many fewer resources on the same task. Researchers have demonstrated learning at a rate that is a 1 million times improvement compared with other typical neural network devices.

The self-learning capabilities prototyped by this test chip have huge potential to improve automotive and industrial applications as well as personal robotics – any application that would benefit from the autonomous operation and continuous learning in an unstructured environment. For example, recognizing the movement of a car or bike for an autonomous vehicle. More importantly, it is up to 1,000 times more energy-efficient than general purpose computing.

Features

  • Fully asynchronous neuromorphic many core mesh.
  • Each neuron capable of communicating with thousands of other neurons.
  • Each neuromorphic core includes a learning engine that can be programmed to adapt network parameters during operation.
  • Fabrication on Intel’s 14 nm process technology.
  • A total of 130,000 neurons and 130 million synapses.
  • Development and testing of several algorithms with high algorithmic efficiency for problems including path planning, constraint satisfaction, sparse coding, dictionary learning, and dynamic pattern learning and adaptation.

TE

Terahertz Electronics – Way To Bridge The largely-untapped Region Between 100GHz and 10THz

The terahertz (THz) region, which is based on 1THz frequency, separates electronics from photonics and has been difficult to access for ages. Semiconductor electronics cannot handle frequencies equal to or greater than 100GHz due to various transport-time related limitations. In other hand, photonics devices fail to work below 10THz as photon’s energy significantly drops to thermal energy. Terahertz Electronics (TE) is a new technology that extends the range of electronics into the THz-frequency region.

The Terahertz Gap
The Terahertz Gap

The main goal of Terahertz Electronics is to build a bridge between low-frequency “Electronics” and high-frequency “Photonics”. Since these devices use photon-electron particle interactions, as photon energy “hv” decreases below thermal energy “kT”, the device ceases to operate efficiently unless it is cooled down. At the low-frequency end, electronics cannot operate above 100GHz as transport time is dependent on drift and diffusion speeds of electrons/holes. As a result, a large region between 100GHz and 10THz remained inaccessible. Terahertz Electronics solves this problem efficiently by cleverly incorporating electronics with photonics.

Terahertz electronics technology offers practical applications in high-speed data transfer, THz imaging, and highly-integrated radar and communication systems. Surprisingly enough, It does not use semiconductors. Instead, it is based on metal-insulator tunneling structures to form diodes for detectors and ultra-high-speed transistors for oscillator based transmitters.

One drawback of the Terahertz Electronics is, it requires high-frequency radiation sources. Lack of a small, low-cost, moderate-power THz source is one of the main reasons that THz applications have not fully materialized yet. Scientists are trying to find a solution to this problem. They created a compact device that can lead to portable, battery-operated sources of THz radiation. This new solid-state T-ray source uses high-temperature superconducting crystals that contain stacks of Josephson junctions. So, even a small voltage, around two millivolts per junction, can induce frequencies in the THz range.

Mercury arc lamps generate light in terahertz
Mercury arc lamps generate light in terahertz

TE devices are extremely fast and they are made entirely of thin-film materials—metals and insulator. Hence, it is possible to fabricate Terahertz Electronics devices on top of complementary metal oxide semiconductor (CMOS) circuitry—a technology for creating integrated-circuits circuitry or on an extensive variety of substrate materials. In TE devices, charge transport through the junction occurs via electron tunneling. Further research and development will make Terahertz Electronics a reality in not-so-distant future.

enlarged cross-section of an experimental chip made of ultrathin semiconductors

New Ultrathin Semiconductors Can Make More Efficient and Ten Times Smaller Transistors Than Silicon

The researchers at Stanford University have discovered two ultrathin semiconductors – hafnium diselenide and zirconium diselenide. They share or even exceed some of the very important characteristics of silicon. Silicon has a great property of forming “rust” or silicon dioxide (SiO2) by reacting with oxygen. As the SiO2 acts as an insulator, chip manufacturers implement this property to isolate their circuits on a die. The most interesting fact about these newly discovered semiconductors is, they also form “rust” just like silicon.

enlarged cross-section of an experimental chip made of ultrathin semiconductors
An enlarged cross-section of an experimental chip made of ultrathin semiconductors

The new materials can also be contracted to functional circuits just three atoms thick and they require much less energy than silicon circuits. Hafnium diselenide and zirconium diselenide “rust” even better than silicon and form so-called high-K insulator. The researchers hope to use these materials to design thinner and more energy-efficient chips for satisfying the needs of future devices.

Apart from having the ability to “rust”, the newly discovered ultrathin semiconductors also have the perfect range of energy band gap – a secret feature of silicon. The band gap is the energy needed to switch transistors on and it is a critical factor in computing. Too low band gap causes the circuits to leak and make unreliable. Too high and the chip takes excessive energy to operate and becomes inefficient. Surprisingly, Hafnium diselenide and zirconium diselenide are in the same optimal range of band gap as silicon.

All this and the diselenides can also be used to make circuits which are just three atoms thick, or about two-thirds of a nanometer, something silicon can never do. Eric Pop, an associate professor of electrical engineering, who co-authored with post-doctoral scholar Michal Mleczko in a study paper, said,

Engineers have been unable to make silicon transistors thinner than about five nanometers, before the material properties begin to change in undesirable ways.

If these semiconductors can be integrated with silicon, much longer battery life and much more complex functionality can be achieved in consumer electronics. The combination of thinner circuits and desirable high-K insulation means that these ultrathin semiconductors could be made into transistors 10 times tinier than anything possible with silicon today. As Eric Pop said,

There’s more research to do, but a new path to thinner, smaller circuits – and more energy-efficient electronics – is within reach.

VO2 Based Mott - MEMS Mirror Actuator

Researchers Developed VO2 Based MEMS Mirror Actuator That Requires Very Low Power

A joint research by the US Air Force Research Laboratory Sensors Directorate and Michigan State University have developed micro-electromechanical systems (MEMS) actuator based on smart materials, specifically vanadium dioxide (VO2). In the room temperature, Vanadium dioxide exhibits the Mott transition. It is a not-well-understood phenomenon known to occur in transition metal chalcogenides and transition metal oxides.

VO2 Based Mott - MEMS Mirror Actuator
VO2 Based Mott – MEMS Mirror Actuator

The research team was able to use VO2 thin films for making complex mirror support structures to create a programmable tilting mirror. Transition-metal oxides like VO2 require little energy to drive the transition and less than more conventional actuation technologies. This enables implementation of transition-metal oxide based MEMS in battery powered and mobile devices.

When an input voltage of 1.1V is applied, the mirror platform achieves the maximum vertical displacement of 75 microns. The average power consumption per mirror actuator is 6.5mW and the total power consumption is 26.1mW for the entire device. The Mott-MEMS actuator mirror showed vertical movements and tilt angles of 75 micrometers and 5.5 degrees, respectively.

While testing, vanadium dioxide (VO2) displayed hysteric behavior or memory effect. That means the current response to externally applied electrical force is dependent on the previous response. Such behavior will let the researchers predict its response nature for certain electrical signals and they can program the actuators to generate different types of responses.

Nelson Sepulveda, a professor of electrical and computer engineering at Michigan State University, said in a statement issued by Wright-Patterson Air Force Base,

The actuation of such devices using smart phase-change materials represents a new operating principle that enables their programming and reduces power consumption.

The study opened a new door in the development of MEMS mirror actuation technology, which could incorporate the use of the hysteresis of smart materials like VO2 for programming tilt angles and vertical displacements in MEMS mirrors. The researchers are focusing on developing programmable MEMs mirrors and improving the design to achieve more precise control and larger movements.

Rechargeable Magnesium Batteries – Safer And Cheaper Than Li-ion Batteries

Researchers at the University of Houston reported in the journal Nature Communications the discovery of a new design that significantly improves the development of a battery based on magnesium. Magnesium batteries are considered as safe resources of power supply – unlike traditional lithium-ion batteries. They are not flammable or subject to exploding – but their ability to store energy is very limited. But the latest discovery of the new design for the battery cathode drastically increases the storage capacity.

Energy diagrams for the intercalation and diffusion of Mg2+ and MgCl+
Energy diagrams for the intercalation and diffusion of Mg2+ and MgCl+ in magnesium batteries

In order to make magnesium batteries, the magnesium-chloride bond must be broken before inserting magnesium into the host, and this is very hard to do. Hyun Deog Yoo, the first author of the paper, said,

First of all, it is very difficult to break magnesium-chloride bonds. More than that, magnesium ions produced in that way move extremely slowly in the host. That altogether lowers the battery’s efficiency.

The new battery technology stores energy by inserting magnesium monochloride into titanium disulfide, which acts as a host. By keeping the magnesium-chloride bond intact, the cathode showed much faster diffusion than traditional magnesium batteries.

The researchers managed to achieve a storage capacity density of 400 mAh/g – a quadruple increase compared with 100 mAh/g for earlier magnesium batteries. This achievement even overpowered the 200 mAh/g cathode capacity of commercially available lithium-ion batteries. Yoo, who is also the head investigator with the Texas Center for Superconductivity at UH, confirmed this fact.

The cell voltage of a magnesium cell is only 1V which is significantly less than a lithium-ion battery which has 3.7V cell voltage. Higher cell voltage and high cathode capacity made Li-ion batteries the standard. Li-ion batteries suffer from an internal structural breach, known as dendrite growth what makes them catch fire. Being an earth-abundant material, magnesium is less expensive than lithium and is not prone to dendrite growth.

The magnesium monochloride molecules are too large to be inserted into the titanium disulfide using conventional methods. The trick they developed is to expand the titanium disulfide to allow magnesium chloride to be inserted rather than breaking the magnesium-chloride bonds and inserting the magnesium alone. Retaining the magnesium-chloride bond doubled the charge the cathode could store. Yoo said,

We hope this is a general strategy. Inserting various polyatomic ions in higher voltage hosts, we eventually aim to create higher-energy batteries at a lower price, especially for electric vehicles.

Coulomb Transistor — A New Concept Where Metal Nanoparticles Are Used In Place Of Semiconductor

A research group at the University of Hamburg has created a unique coulomb transistor that operates on the principle of the voltage control of the electron band gap in metallic quantum-dot nanoparticles. This Single-electron transistor represents an approach to develop less power-consuming microelectronic devices. It will be possible if industry-compatible fabrication and room temperature operation are achieved.

The concept is based on building stripes of small, colloidal, metal nanoparticles on a back-gate device architecture. Being very tiny, the metallic nanoparticles exhibit semiconductor properties that can be controlled by voltage. The body of this transistor can be operated as a second gate. It results in well-defined and controllable transistor characteristics.

Design of coulomb transistor
Design of Coulomb transistor

This newly invented Coulomb transistor has three main advantages. The advantages are: on/off ratios above 90%, very reliable and sinusoidal Coulomb oscillations, and room temperature operation. The concept allows for tuning of the device properties such as Coulomb energy gap and threshold voltage, as well as the period, position, and strength of the oscillations.

Though the single-electron transistor (SET) is quite similar to a common field-effect transistor (FET), it does not rely on the semiconductor band gap but instead on the Coulomb energy gap. Transfer characteristics of the SET show periodic on and off states known as Coulomb oscillations. Researchers hope that might render new applications possible in the future.

When a bias voltage is applied to the nanoparticle channel, it becomes clear that conduction in this system is not purely metallic but is controlled by tunnel barriers between individual particles. The transport of charged particles is hindered due to very high potential barrier which depends on the charging energy. Tuning the voltage of an additional gate results in a field effect that continuously shifts the energy levels of the particles and allows for tunneling to occur. This additional gate electrode is separated from the channel by a dielectric layer.

Output characteristics of coulomb transistor
Output characteristics of Coulomb transistor

The single-electron transistors require further research and more development, but the work shows that there are alternatives to traditional transistor concepts that can be used in the future in various fields of application. Christian Klinke, the lead researcher, said in a statement,

The devices developed in our group can not only be used as transistors, but they are also very interesting as chemical sensors because the interstices between the nanoparticles, which act as so-called tunnel barriers, react highly sensitive to chemical deposits.

Graphene Electronic Circuits with Atomic Precision

Essential electronic components, such as diodes and tunnel barriers, can be incorporated in single graphene wires (nanoribbons) with atomic precision. The result is a working electronic device that could be used in Graphene-based electronic switches with extremely fast operational speeds. Chemists at Utrecht University made this discovery together with their colleagues at TU Delft and the Aalto University in Finland.

Metal-semiconductor-metal junction (tunnel barrier) incorporated into a single graphene nanoribbon

The ‘wonder material’ graphene has many interesting characteristics, and researchers around the world are hard at work looking for new ways to utilise them. Graphene itself does not have the characteristics  to switch electrical currents on and off, however, so smart solutions must be found for that particular problem.

“The great thing about our solution is its atomic precision. By selecting certain precursor substances (molecules), we can code the structure of the electrical circuit with extreme accuracy”, explains research leader Ingmar Swart from Utrecht University.

The chemical pathway to graphene electronic circuits

Seamless Integration

The switch structureded on the principle of graphene nanoribbons. Previous research has shown that the ribbon’s electronic characteristics are dependent on its atomic width. A ribbon that is five atoms wide is an ordinary electric wire with extremely good conduction characteristics, but adding two atoms makes the ribbon a semiconductor.

“We are now able to seamlessly integrate a five-atom wide ribbon together with one that is seven atoms wide. That gives you a metal-semiconductor junction, which works as a diode”, according to Swart.

The work is published in Nature Communications, you can check it out on this link.

Water Splitting With Solar Energy

Using solar energy to split water provides an efficient way for large scale renewable energy conversion and storage. A group of researchers from TUDelft and AMOLF have successfully developed an efficient and stable photo-electrode that could improve water splitting with solar energy.

Decomposition of water using solar energy

This photoelectrode absorbs light and directly decomposes water into hydrogen and oxygen. In addition to the efficiency, the system is also cheap because of using silicon wafers as the light absorbing material.

The Process

Photoelectrochemical (PEC) splitting of water is a direct conversion of solar to chemical energy to produce renewable and clean fuel. The hydrogen, for example, can be used directly in fuel cells, or combined with other molecules to create durable materials.

Together with colleagues from AMOLF (Amsterdam), we have engineered a photo-electrode, a material that absorbs light and directly splits water, that has a very high efficiency and over 200 hours of stability’, says Wilson Smith, Associate Professor in the Department of Chemical Engineering at TU Delft. ‘This is remarkable in a field where people normally show only a few hours of stability.  We use silicon wafers as the light absorbing material, so the photoelectrode is also very cheap.

Researchers had also designed a new insulator layer to stabilize the semiconductor (Si) photo-electrode, while keeping the high efficiency of water splitting by using two metals. This approach known as making a metal-insulator-semiconductor (MIS) junction. It is a simple system that combines the stability and catalysis bottlenecks in photoelectrochemical water splitting.

For more information, the researchers had published this research in Nature Communications.

Smallest Satellite Ever Sent & Operated in Orbit By Breakthrough Starshot

Breakthrough Starshot is a research and engineering project by Breakthrough Initiatives to develop a proof-of-concept fleet of light sail spacecraft, named StarChip, capable of making the journey to the Alpha Centauri star system, 4.37 light-years away, at speeds between 15% and 20% of the speed of light, taking between 30 and 20 years to get there, respectively, and about 4 years to notify Earth of a successful arrival.

The project was announced on 12 April 2016 in an event in New York City by physicist and venture capitalist Yuri Milner and cosmologist Stephen Hawking who is serving as board member of the initiatives. Other board members include Facebook CEO Mark Zuckerberg. The project has an initial funding of US$100 million to start research. Milner places the final mission cost at $5–10 billion, and estimates the first craft could launch around 2036.

It is now in orbit!

On June 23, the initiative sent the tiniest-ever satellites into orbit. Thanks to an Indian rocket, 6 of these satellites, as named as Sprites, went to space. Some of them were attached to larger satellites: : the Latvian Venta satellite and the Italian Max Valier satellite which will release the other four Sprites to orbit once communications are achieved.

In fact, each Sprite contains a computer processor, solar panels, a magnetometer, a gyroscope, and a radio for communicating with researchers on Earth and all in a size of  3.5×3.5 cm circuit board.
Until now, only one signal came from on of the 2 Sprites. Since the Max Valier hasn’t established a connection yet, the remaining Sprites didn’t detach. Usually the satellite should receive a command to release its cargo, and this is not possible without a functioning antenna.
Despite the humble results, the team is feeling victorious. Having these small and cheap satellites hovering over the space and doing part of the job is an achievement.
These tiny satellites can go along on a planetary exploration mission and start deployment once they get there. By using these satellites, the risk of sending large spacecrafts will diminish.
 To find more details about the Breakthrough Starshot, check out this official website.