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Microwave photonics chip uses optics for analog computation

Thu, 07 Mar 2024 00:00:00 +1100

A research team led by Professor Wang Cheng from the Department of Electrical Engineering (EE) at City University of Hong Kong (CityUHK) has developed a world-leading microwave photonic chip that is capable of performing ultrafast analog electronic signal processing and computation using optics.

Researchers from City University of Hong Kong (City UHK) have developed a microwave photonic chip that is capable of performing ultra-fast analog electronic signal processing and computation using optics. The chip, which is reportedly 1000 times faster and consumes less energy than a traditional electronic processor, has a range of applications in areas such as 5/6G wireless communication systems, high-resolution radar systems, artificial intelligence, computer vision and image/video processing.

The research findings have been published in the scientific journal Nature. The expansion of wireless networks, the Internet of Things and cloud-based services has placed significant demands on underlying radio frequency systems. Microwave photonics (MWP) technology, which uses optical components for microwave signal generation, transmission and manipulation, offers solutions to these challenges. However, integrated MWP systems struggle to achieve ultrahigh speed analog signal processing with chip-scale integration, high fidelity and low power simultaneously.

Professor Wang Cheng from CityUHK said the researchers developed an MWP system that combines ultrafast electro-optic (EO) conversion with low-loss, multifunctional signal processing on a single integrated chip. This was achieved by using an integrated MWP processing engine based on a thin-film lithium niobate (LN) platform capable of performing multi-purpose processing and computation tasks of analog signals.

The team has been researching the integrated LN photonic platform for years; in 2018, the researchers developed a CMOS (complementary metal-oxide semiconductor)-compatible integrated electro-optic modulator on the LN platform, which laid the foundation for the current research. LN is referred to as the “silicon of photonics” for its importance to photonics comparable to silicon in microelectronics.

Feng Hanke, first author of the paper, said the chip can perform high-speed analog computation with ultrabroad processing bandwidths of 67 GHz and enhanced computation accuracies. This research opens up a new research field (LN microwave photonics) that could facilitate the development of microwave photonics chips with compact sizes, high signal fidelity and low latency.

Image credit: iStock.com/krystiannawrocki

CSIRO launches printed flexible solar cells into space

Thu, 07 Mar 2024 00:00:00 +1100

Printed flexible solar cell technology developed by Australia’s national science agency, CSIRO, has been launched into space aboard an Australian private satellite, Optimus-1, on Space X’s Transporter-10 mission. CSIRO is exploring the potential of printed flexible solar cells as an energy source for future space endeavours, in collaboration with Australian space transportation provider Space Machines Company. A major challenge that impedes the development of spacecraft is low-mass, high-efficiency power systems.

CSIRO Space Program Director Dr Kimberly Clayfield said the printed flexible solar cells could provide a reliable, lightweight energy solution for future space operations and exploration. “If the space flight test reveals similar performance as we’ve shown in the lab, this technology offers significant advantages over traditional silicon-based solar,” Clayfield said.

The printed flexible solar cell technology was successfully launched into space aboard Australian private satellite Optimus-1. Image credit: Space Machines Company.

CSIRO Renewable Energy Systems Group Leader Dr Anthony Chesman said eight mini-modules of CSIRO’s printed flexible solar cells were attached to the surface of the Optimus-1 satellite. “CSIRO researchers have been working for many years to improve our solar cell performance using perovskite — an advanced material that is highly efficient in converting sunlight into energy. Our perovskite cells have been achieving incredible outcomes on earth and we’re excited that they’ll soon be showcasing their potential in space,” Chesman said.

Rajat Kulshrestha, CEO of Space Machines Company, said the innovative flexible solar cells will transform spacecraft power systems and enable new possibilities for future space missions. “Through perseverance and teamwork, our engineers and scientists, alongside partners like CSIRO, have created something truly groundbreaking. We’re thrilled to integrate this groundbreaking technology into Optimus,” Kulshrestha said.

According to Chesman, in situ testing will provide information on the performance of the perovskite solar cells as they orbit the planet. The researchers will gain information on how the panels are holding up under extreme conditions in space and data on the efficiency they achieve. The team has already undertaken research on the likely performance of the cells in a space environment.

“Based on our research we expect our printed flexible solar cells will stand up to the effects of cosmic electron and gamma radiation, which can compromise the performance and integrity of traditional solar cells. We are also confident these cells will outperform traditional cells in cases where sunlight hits them at non-optimal angles,” Chesman said.

The researchers will use the feedback received from the satellite to gain insights into the practical application of the printed flexible solar cell technology, thereby informing future development. “This is a great opportunity for Australian technology to contribute to global space exploration. We are eager to collaborate with potential partners to explore this further,” Chesman said.

The research exploring the potential of printed flexible solar cells in space was published in the journal ACS Applied Energy Materials.

Top image caption: Eight mini-modules of CSIRO’s Australian-made printed flexible solar cells were attached to the surface of Space Machine Company’s Optimus-1 satellite. Image credit: CSIRO.

Nanothin memory chips manufactured with 2D printing

Wed, 06 Mar 2024 00:00:00 +1100

Engineering researchers from the University of Sydney have developed a 2D printing process using liquid metals that could create new ways of creating more advanced and energy-efficient computing hardware that is manufactured at the nanoscale. The development comes amid increasing demand for memory devices, which require significant amounts of energy to produce and use.

Dr Mohammad Ghasemian, the study’s lead author, said reducing the temperature at which zirconium and hafnium become liquid is crucial for developing lower-cost electrical devices, as less energy is required. The researchers first combined tin, zirconium and hafnium in a precise ratio, thus allowing the alloy to be melted below 500°C, lower than the individual melting points for zirconium (1855°C) and hafnium (2227°C).

The liquid metal alloy has a thin oxide layer while maintaining a liquid centre, and is used to harvest the ultra-thin tin oxide nanosheets doped with hafnium zirconium oxide. “Tin is abundant, low-cost and can be used at a large scale for the manufacture of critical semiconductors, transistors and memory chips. Though hafnium zirconium oxide is a well-known ferroelectric material used in nanoscale applications, like memory devices and sensors, obtaining nanosheets using conventional techniques is both difficult and costly,” Ghasemian said.

The researchers applied the tin-zirconium-hafnium alloy to harvest the nanothin tin oxide layer doped with hafnium zirconium oxide through exfoliation — lifting it from its liquid surface — so it could then be 2D printed on a substrate as ferroelectric nanosheets. These sheets are designed to form the basis of next-generation computing hardware, such as semiconductors and memory chips. Ghasemian likened the alloy to a marble coated in ink.

“The alloy is like a solvent that allows us to remove that ink and then use it for printing. Our process allows us to harvest this precious crust layer and turn it into ultra-thin sheets, which are then used to manufacture electronics. It could be a new source of functional 2D materials which are not accessible by conventional methods. This process allows us to introduce ferroelectricity into much smaller, 2D metal oxides, allowing for the development of next-generation nanoelectronics at low temperatures,” Ghasemian said.

The research findings were published in the journal Small.

Image credit: iStock.com/sefa ozel

FIDO tech boosts stability of perovskite solar cells

Wed, 06 Mar 2024 00:00:00 +1100

Researchers at Nagoya University in Japan have created a material based on fullerene indanones (FIDO) that could improve the durability of next-generation solar cells. The researchers published their findings in the Journal of the American Chemical Society.

The next-generation of solar cells will potentially use perovskite-based cells. These crystal-based cells are efficient and can even generate electricity indoors under weak light conditions. They are also lighter and more flexible than conventional silicon solar cells and are therefore suitable for installation on vertical surfaces, such as windows and walls.

Many of the unique properties of these solar cells come from fullerene (C60). Shaped like soccer balls, fullerenes are carbon-based semiconductors that can channel electrons to create power, making them essential for organic electronics. Researchers can attach organic molecules to fullerenes to enhance their electronic function, thereby creating derivatives with different properties. The researchers, led by Professor Yutaka Matsuo, added indanone to fullerene to create FIDOs.

Indanone is a useful compound in reactions and has a unique structure of fused rings that create strong carbon links between the fullerene and the benzene part of the indanone. This creates an arrangement with excellent stability even when heated. Using FIDO, the researchers controlled the film to create an amorphous material instead of the more common crystalline material found in silicon solar cells. Amorphous materials have a more random structure than carefully organised crystals; this allows amorphous films to be engineered to have specific properties by adjusting the deposition conditions and tailoring the electrical characteristics of the film to meet the requirements of solar cell technology.

When compared with a standard film, the researchers found that the new film was more efficient and stable; these properties also did not degrade. There was also no decrease in conversion efficiency. Matsuo said the amorphous film did not crystallise upon heating and showed excellent morphological stability.

“A problem with films is that when heated to 150°C, the degree of crystallisation increases. Our newly developed film is an amorphous thin film after deposition and remains amorphous even when heated,” Matsuo said.

This new technique could have a range of applications, as the fullerene derivatives can be used for perovskite solar cells and for photoelectric conversion elements, such as organic photodiodes and organic photodetectors. “Organic photodetectors contribute to the high resolution of imaging sensors in cameras and will be used in fingerprint authentication on smartphone displays, allowing unlocking from any part of the screen touched by a finger,” Matsuo said.

Image credit: iStock.com/deyanarobova

Movies of ultrafast electronic circuitry in space and time

Thu, 29 Feb 2024 00:00:00 +1100

The increasing demand for ever-faster information processing has ushered in a new era of research focused on high-speed electronics operating at frequencies nearing terahertz and petahertz regimes. While existing electronic devices predominantly function in the gigahertz range, the forefront of electronics is pushing towards millimetre waves, and the first prototypes of high-speed transistors, hybrid photonic platforms, and terahertz metadevices are starting to bridge the electronic and optical domains. However, characterising and diagnosing such devices poses a significant challenge due to the limitations of available diagnostic tools, particularly in terms of speed and spatial resolution. How shall one measure a breakthrough device if it’s the fastest and smallest of its kind?

In response to this challenge, a team of researchers from the University of Konstanz now proposes an innovative solution: they create femtosecond electron pulses in a transmission electron microscope, compress them with infrared laser light to merely 80-femtosecond duration, and synchronise them to the inner fields of a laser-triggered electronic transmission line with the help of a photoconductive switch. Then, using a pump-probe approach, the researchers directly sense the local electromagnetic fields in their electronic devices as a function of space and time. This new kind of ultrafast electron beam probe provides femtosecond, nanometre and millivolt resolutions under normal operating conditions, ie, without affecting the in situ operation of the device. Only the substrate material needs to be thinned out to become transparent to the electron beam.

This femtosecond electron beam probe approach opens up new frontiers in the research and development of next-generation electronics because diagnostic resolutions are now, in principle, only limited by the de Broglie wavelength of the electrons in the microscope and the cycle period of the infrared laser light that is applied for the all-optical electron pulse compression. With such resolutions, the new tool offers unprecedented insight into future electronic circuitry and can guide their design towards novel applications. The new concept’s versatility and seamless integration into existing electron-beam inspection devices in the semiconductor industry should make it a promising asset for advancing ultrafast electronics towards unexplored capacities.

This is a modified version of a news item published by the University of Konstanz. The original version of the news item can be accessed here.

Image credit: iStock.com/Panuwat Sikham

Researchers reveal spin-orbit effects on exciton complexes in diamond

Thu, 29 Feb 2024 00:00:00 +1100

Diamonds have a range of industrial applications, such as in solid-state electronics. New technologies aim to provide high-purity synthetic crystals to act as semiconductors when doped with impurities as electron donors or acceptors of other elements. These extra electrons — or holes — do not participate in atomic bonding but sometimes bind to excitons in semiconductors and other condensed matter. Doping may cause physical changes, but how the exciton complex — a bound state of two positively charged holes and one negatively charged electron — manifests in diamonds doped with boron is unconfirmed, as two conflicting interpretations exist of the exciton’s structure.

Now, a team of researchers led by Kyoto University has determined the magnitude of the spin-orbit interaction in acceptor-bound excitons in a semiconductor. Team leader Nobuko Naka from Kyoto University said the researchers broke through the energy resolution limit of conventional luminescence measurements by observing the fine structure of bound excitons in boron-duped blue diamond, using optical absorption.

“We hypothesised that, in an exciton, two positively charged holes are more strongly bound than an electron-and-hole pair. This acceptor-bound exciton structure yielded two triplets separated by a spin-orbit splitting of 14.3 meV, supporting the hypothesis,” said first author Shinya Takahashi.

Luminescence resulting from thermal excitation can be used to observe high-energy states, but this measurement method broadens spectral lines and blurs ultra-fine splitting. Instead, the researchers cooled the diamond crystal to cryogenic temperatures, obtaining nine peaks on the deep-ultraviolet absorption spectrum, compared to the usual four using luminescence. The researchers also developed an analytical model including the spin-orbit effect to predict the energy positions and absorption intensities. Going forward, the researchers are considering the possibility of measuring absorption under external fields, leading to further line splitting and validation due to the changes in symmetry.

“Our results provide useful insights into spin-orbit interactions in systems beyond solid-state materials, such as atomic and nuclear physics. A deeper understanding of materials may improve the performance of diamond devices, such as light-emitting diodes, quantum emitters and radiation detectors,” Naka said.

Image caption: Highly precise optical absorption spectra of diamond reveal ultra-fine splitting. Image credit: KyotoU/Nobuko Naka.

Researchers develop high efficiency quantum dot solar cells

Thu, 29 Feb 2024 00:00:00 +1100

A team of researchers has unveiled a novel ligand exchange technique that enables the synthesis of organic cation-based perovskite quantum dots (PQDs), providing exceptional stability while suppressing internal defects in the photoactive layer of solar cells. The research findings could propel the development of an efficient quantum dot (QD) solar cell and thereby facilitate the commercialisation of next-generation solar cells.

Professor Sung-Yeon Jang, the lead researcher from UNIST, said the technology has achieved an 18.1% efficiency in QD solar cells. “This remarkable achievement represents the highest efficiency among quantum dot solar cells recognised by the prestigious National Renewable Energy Laboratory (NREL) in the United States,” Jang said.

QDs are semiconducting nanocrystals with typical dimensions ranging from several to tens of nanometres, capable of controlling photoelectric properties based on their particle size. PQDs, in particular, have garnered attention from researchers due to their outstanding photoelectric properties. Their manufacturing process involves simple spraying or application to a solvent, eliminating the need for the growth process on substrates. This approach allows for high-quality production in various manufacturing environments.

However, using QDs as solar cells requires a technology that reduces the distance between QDs through ligand exchange, a process that binds a large molecule, such as a ligand receptor, to the surface of a QD. Organic PQDs face challenges, including defects in their crystals and surfaces during the substitution process. As a result, inorganic PQDs with limited efficiency (of up to 16%) have predominantly been used as materials for solar cells.

The researchers used an alkyl ammonium iodide-based ligand exchange strategy, thereby substituting ligands for organic PQDs with excellent solar utilisation. This enabled the creation of a photoactive layer of QDs for solar cells with high substitution efficiency and controlled defects. As a result, the efficiency of the PQDs, which was previously limited to 13%, was improved to 18.1%. The solar cells also demonstrated stability, maintaining their performance after long-term storage for over two years. The new organic PQD solar cells exhibited high efficiency and stability simultaneously.

“This study presents a new direction for the ligand exchange method in organic PQDs, serving as a catalyst to revolutionise the field of QD solar cell material research in the future,” Jang said.

The research findings have been published online in Nature Energy.

Image credit: iStock.com/Milos-Muller

Wearable sticker enables communication through gestures

Thu, 29 Feb 2024 00:00:00 +1100

Researchers have developed a wearable sensor that allows users to turn their hand or finger movement into communication without having to say a word or tap a touchscreen. The sensor could open new possibilities for rehabilitation applications and help those with disabilities communicate more easily.

The sensor combines a soft and flexible material called polydimethylsiloxane, or PDMS, with an optical component known as a fiber Bragg grating (FBG). The sensor is designed to be comfortable for long-term wear while having the ability to detect movements with accuracy.

Kun Xiao from Beijing Normal University said the sensors could translate gestures or facial expressions into words or commands, enabling those with severe mobility or speech issues to communicate with others or interact with technology more easily. “For someone recovering from a stroke, these sensors could monitor wrist, finger or even facial movements to monitor their rehabilitation progression,” Xiao said.

The cross-disciplinary team of researchers from Beijing Normal University, Sun Yat-sen University and Guilin University of Electronic Technology described the new sensor in the journal Biomedical Optics Express. The sensor reportedly shows a high level of sensitivity and accuracy during tests involving gesture recognition and communication assistance. Researchers believe that the sensors could be tailored for applications such as monitoring other health indicators like respiratory or heart rate by detecting subtle body movements. They could also be useful for athletes or fitness enthusiasts to monitor and improve their form or technique in real time.

The researchers used PDMS, a type of silicone elastomer that is flexible and skin friendly, to develop the sensor. This enables the sensor to be worn for long periods without irritation or discomfort. To give the sensor its movement-sensing capability, the researchers embedded the PDMS with FBGs, a type of reflector that is etched into a short segment of optical fibre to reflect specific wavelengths while transmitting all the others. The sensor makes it possible to detect slight changes in the way light propagates through the fibre optic during movement, allowing the system to detect specific movements by analysing the alterations in light behaviour.

When developing the sensor, the researchers found that using a thicker PDMS patch caused a more pronounced wavelength shift. Leveraging this sensitivity-enhancing effect of PDMS allowed the optical sensors to detect subtle movements, like the bend of a finger. The sensors can be applied to various parts of the body for a range of applications. The researchers are also developing a calibration method that allows the sensors to be tailored to each user, making them adaptable to various applications.

Image caption: Researchers have developed a wearable PDMS sensor that uses an FBG to sense movements. The sensors could be used to monitor wrist, finger or even facial movements. Image credit: Kun Xiao, Beijing Normal University in China.

Electronex Expo returns to Sydney for 2024

Tue, 27 Feb 2024 00:00:00 +1100

Following the success of 2023’s Electronex — the Electronics Design and Assembly Expo, the event will return to Sydney in 2024, taking place in the Rosehill Event Centre from 19–20 June. The 2023 event featured more than 80 exhibitors and was attended by over 1900 trade visitors; now, the Sydney event is also close to selling out.

Electronex is Australia’s only major exhibition for companies using electronics in design, assembly, manufacture and service. The SMCBA Electronics Design and Manufacture Conference will also be held alongside Electronex, featuring technical workshops from international and local experts.

Electronex will feature a range of electronic components, surface mount and inspection equipment, test and measurement and other ancillary products and services from local and international suppliers. Attendees will also be able to talk to contract manufacturers that can design and produce turnkey solutions to meet their specific requirements.

Designers, engineers, managers and other design makers who are involved in designing or manufacturing products that utilise electronics are all urged to attend. Many companies will also be launching and demonstrating new products and technology at the event.

Following the success of the inaugural IPC Soldering Competition in Melbourne, this year’s competition will be a round of the IPC World Championship with the winner invited to the finals in November. Further details about the competition will be announced in the lead-up to the event.

The Surface Mount & Circuit Board Association (SMCBA)’s annual conference, dedicated to electronics design and manufacture, will take place in conjunction with Electronex in 2024. The conference will feature a line-up of local and international experts, with David Bergman, Vice President of IPC International, to give the keynote address “Digitalisation of Electronics Manufacturing — Towards Smart Factory enabling Industry 4.0”.

Other presenters at the SMCBA Conference include Mike Creeden, Founder of San Diego PCB Designs; David Hillman from Hillman Electronic Assembly Solutions; Rick Hartley from RHartley Enterprises; and Chris Turner, PSCA Test Engineering SME.

Visitors to the expo can register for free at www.electronex.com.au. For details about the soldering competition and conference visit www.smcba.asn.au.

Chip opens door to AI computing at light speed

Fri, 23 Feb 2024 00:00:00 +1100

Penn Engineers have developed a new chip that uses light waves, rather than electricity, to perform the complex maths essential to training AI. The chip has the potential to radically accelerate the processing speed of computers while also reducing their energy consumption.

The silicon-photonic (SiPh) chip’s design is the first to bring together Benjamin Franklin Medal Laureate and H. Nedwill Ramsey Professor Nader Engheta’s pioneering research in manipulating materials at the nanoscale to perform mathematical computations using light — the fastest possible means of communication — with the SiPh platform, which uses silicon, the cheap, abundant element used to mass-produce computer chips.

The interaction of light waves with matter represents one possible avenue for developing computers that supersede the limitations of today’s chips, which are essentially based on the same principles as chips from the earliest days of the computing revolution in the 1960s.

In a paper in Nature Photonics, Engheta’s group, together with that of Firooz Aflatouni, Associate Professor in Electrical and Systems Engineering, describes the development of the new chip. “We decided to join forces,” said Engheta, leveraging the fact that Aflatouni’s research group has pioneered nanoscale silicon devices.

Their goal was to develop a platform for performing what is known as vector-matrix multiplication, a core mathematical operation in the development and function of neural networks, the computer architecture that powers today’s AI tools.

Instead of using a silicon wafer of uniform height, Engheta explained, “you make the silicon thinner, say 150 nanometres”, but only in specific regions. Those variations in height — without the addition of any other materials — provide a means of controlling the propagation of light through the chip, since the variations in height can be distributed to cause light to scatter in specific patterns, allowing the chip to perform mathematical calculations at the speed of light.

Due to the constraints imposed by the commercial foundry that produced the chips, Aflatouni said, this design is already ready for commercial applications, and could potentially be adapted for use in graphics processing units (GPUs), the demand for which has skyrocketed with the widespread interest in developing new AI systems. “They can adopt the Silicon Photonics platform as an add-on,” Aflatouni said, “and then you could speed up training and classification”.

In addition to faster speed and less energy consumption, Engheta and Aflatouni’s chip has privacy advantages — because many computations can happen simultaneously, there will be no need to store sensitive information in a computer’s working memory, rendering a future computer powered by such technology virtually unhackable. “No one can hack into a non-existing memory to access your information,” Aflatouni said.

This study was conducted at the University of Pennsylvania School of Engineering and Applied science and supported in part by a grant from the U.S. Air Force Office of Scientific Research’s (AFOSR) Multidisciplinary University Research Initiative (MURI) to Engheta and a grant from the U.S. Office of Naval Research (ONR) to Aflatouni.

Additional co-authors include Vahid Nikkhah, Ali Pirmoradi, Farshid Ashtiani and Brian Edwards of Penn Engineering.

Image credit: iStock.com/da-kuk

Li-ion conductor discovery unlocks new direction for sustainable batteries

Wed, 21 Feb 2024 00:00:00 +1100

One of the grand challenges for materials science is the design and discovery of new materials that address global priorities such as net zero.

In a paper published in the journal Science, researchers at the University of Liverpool have discovered a solid material that rapidly conducts lithium ions. Such lithium electrolytes are essential components in the rechargeable batteries that power electric vehicles and many electronic devices.

Consisting of non-toxic earth-abundant elements, the new material has high enough Li-ion conductivity to replace the liquid electrolytes in current Li-ion battery technology, improving safety and energy capacity.

Using a transformative scientific approach to design the material, the interdisciplinary research team from the university synthesised the material in the laboratory, determined its structure (the arrangement of the atoms in space) and demonstrated it in a battery cell.

The new material is one of a very small number of solid materials that achieve Li-ion conductivity high enough to replace liquid electrolytes, and operates in a new way because of its structure.

Its discovery was achieved through a collaborative computational and experimental workflow that used AI and physics-based calculations to support decisions made by chemistry experts at the university.

The new material provides a platform for the optimisation of chemistry to further enhance the properties of the material itself, and to identify other materials based on the new understanding provided by the study.

Professor Matt Rosseinsky, from the University of Liverpool’s Department of Chemistry, said, “This research demonstrates the design and discovery of a material that is both new and functional. The structure of this material changes previous understanding of what a high-performance solid-state electrolyte looks like.

“Specifically, solids with many different environments for the mobile ions can perform very well, not just the small number of solids where there is a very narrow range of ionic environments. This dramatically opens up the chemical space available for further discoveries.

“Recent reports and media coverage herald the use of AI tools to find potentially new materials. In these cases, the AI tools are working independently and thus are likely to recreate what they were trained on in various ways, generating materials that may be very similar to known ones.

“In contrast, this discovery research paper shows that AI and computers marshalled by experts can tackle the complex problem of real-world materials discovery, where we seek meaningful differences in composition and structure whose impact on properties is assessed based on understanding.

“Our disruptive design approach offers a new route to discovery of these and other high-performance materials that rely on the fast motion of ions in solids.”

The study undertaken was a combined effort between researchers in University of Liverpool’s Department of Chemistry, Materials Innovation Factory, Leverhulme Research Centre for Functional Materials Design, Stephenson Institute for Renewable Energy, Albert Crewe Centre and School of Engineering.

The work was funded by the Engineering and Physical Sciences Research Council (EPSRC), the Leverhulme Trust and the Faraday Institution.

Image caption: Image represents the lithium ions (in blue) moving through the structure. Image credit: University of Liverpool.

New 300 GHz transmitter enhances 6G and radar technologies

Wed, 21 Feb 2024 00:00:00 +1100

A team of researchers led by Professor Kenichi Okada from Tokyo Institute of Technology (Tokyo Tech) and NTT Corporation have developed a 300 GHz band transmitter that could pave the way for many technological applications, including body and cell monitoring, radar, 6G wireless communications and terahertz sensors.

At present, most frequencies above the 250 GHz mark remain unallocated. Accordingly, many researchers are developing 300 GHz transmitters/receivers to capitalise on the low atmospheric absorption at these frequencies, as well as the potential for extremely high data rates that comes with it. However, high-frequency electromagnetic waves become weaker at a fast pace when travelling through free space. To combat this problem, transmitters must achieve a large effective radiated power. While some interesting solutions have been proposed, it is challenging for a 300 GHz-band transmitter manufactured via conventional CMOS processes to simultaneously realise high output power and small chip size.

The proposed solution from Tokyo Tech is a phased-array transmitter composed of 64 radiating elements, which are arranged in 16 integrated circuits with four antennas each. Since the elements are arranged in three dimensions by stacking printed circuit boards (PCBs), this transmitter supports 2D beam steering. As a result, the transmitted power can be aimed both vertically and horizontally, allowing for fast beam steering and tracking receivers efficiently.

The researchers used Vivaldi antennas, which can be implemented directly on-chip and have a suitable shape and emission profile for high frequencies. Another feature of the proposed transmitter is its power amplifier (PA)-last architecture. By placing the amplification stage before the antennas, the system only needs to amplify signals that have already been conditioned and processed. This leads to higher efficiency and better amplifier performance.

The researchers addressed some common problems that arise with conventional transistor layouts in CMOS processes, such as high gate resistance and large parasitic capacitances. The researchers optimised layout by adding drain paths and vias and by altering the geometry and element placing between metal layers. Okada said that compared to the standard transistor layout, the parasitic resistance and capacitances in the proposed transistor layout are all mitigated. “In turn, the transistor-gain corner frequency, which is the point where the transistor’s amplification starts to decrease at higher frequencies, was increased from 250 to 300 GHz,” Okada said.

The researchers also designed and implemented a multi-stage 300 GHz power amplifier to be used with each antenna. Excellent impedance matching between stages reportedly enabled the amplifiers to demonstrate outstanding performance. “The proposed power amplifiers achieved a gain higher than 20 dB from 237 to 267 GHz, with a sharp cut-off frequency to suppress out-of-band undesired signals,” Okada said. The proposed amplifier also achieved a noise figure of 15 dB which was evaluated by the noise measurement system in 300 GHz band.

The proposed transmitter was tested through simulations and experiments and obtained promising results, achieving a data rate of 108 Gb/s in on-PCB probe measurements. The transmitter also displayed remarkable area efficiency compared to other CMOS-based designs alongside low power consumption, highlighting its potential for miniaturised and power-constrained applications. Notable use cases include sixth-generation (6G) wireless communications, high-resolution terahertz sensors, and human body and cell monitoring.

Image credit: iStock.com/Just_Super

New multicolour 3D printing tech inspired by chameleons

Wed, 21 Feb 2024 00:00:00 +1100

Inspired by the colour-changing ability of chameleons, researchers have developed a sustainable technique to 3D-print multiple, dynamic colours from a single ink.

“By designing new chemistries and printing processes, we can modulate structural colour on the fly to produce colour gradients not possible before,” said Ying Diao, an associate professor of chemistry and chemical and biomolecular engineering at the University of Illinois Urbana-Champaign and a researcher at the Beckman Institute for Advanced Science and Technology.

The study appears in the journal PNAS.

“This work is a great illustration of the power of collaboration,” said co-author Damien Guironnet, an associate professor of chemical and biomolecular engineering.

In this study, Diao and her colleagues present a UV-assisted direct-ink-write 3D printing approach capable of altering structural colour during the printing process by tuning light to control evaporative assembly of specially designed crosslinking polymers.

“Unlike traditional colours which come from chemical pigments or dyes that absorb light, the structural colours abundant in many biological systems come from nano-textured surfaces that interfere with visible light. This makes them more vibrant and potentially more sustainable,” said Sanghyun Jeon, the lead author and a graduate student in the Diao Lab.

The researchers can produce structural colours in the visible wavelength spectrum from deep blue to orange. While an artist might use many different paints to achieve this colour gradient, the research team uses a single ink and modifies how it is printed to create the colour gradient.

“The work shows the benefit of us all having learned from each other by sharing our successes and challenges,” said co-author Simon Rogers, an associate professor of chemical and biomolecular engineering.

“Only by working together could we design this system at the molecular level to yield such fascinating properties," said co-author Charles Sing, an associate professor of chemical and biomolecular engineering and materials science and engineering.

Image caption: Inspired by the colour-changing abilities of chameleons, researchers developed a dynamic and sustainable colour-changing ink seen in this 3D printed chameleon illustration created by the research team. Image credit: Sanghyun Jeon, Diao Lab.

This is a modified version of a news item published by the Beckman Institute for Advanced Science and Technology. The original version of the news item can be accessed here.

Scientists produce ultrathin and stretchable soft electronics

Mon, 19 Feb 2024 00:00:00 +1100

Researchers from Nanyang Technological University (NTU) have established a pilot laboratory capable of rapid prototyping ultrathin and stretchable electronics that detect bioelectric signals from the skin, muscles and organs, and transmit these signals to control robots or other electronic devices.

By attaching these smart sensors to limbs or the head, users with limb disabilities or mobility impairments can control robotic prosthesis, machinery and motorised wheelchairs using alternative muscle movements and bio-signals. These innovative soft electronics were developed by combining in-house designed soft materials and processes with commercially available hardware components. The hybrid combination allows the researchers to integrate many types of sensor on the market, such as wireless connectivity, accelerometer, temperature sensing, and monitoring of vitals like heart rate, blood pressure, oxygen levels and more.

The resulting sensors, encased in a gel-like skin, are soft, flexible and stretchable, similar to silicon bandages used in health care. The sensors adhere to the skin, enable joint movement, and come in various sizes and thicknesses, ranging from centimetres to sub-microns the width of a human hair.

Conventionally, semiconductor manufacturing produces electronics that rely on silicon as the primary substrate or platform. However, silicon is hard and rigid. Soft electronics, instead, use a soft platform such as hydrogels or biocompatible plastics that are stretchable and flexible. To enable electronic circuits to accommodate movement without breaking under repeated stress, these circuits are printed on soft substrates using intricate patterns at the micro and nanoscale, about 10 times thinner than the width of a human hair.

NTU Professor Chen Xiaodong established the pilot laboratory which aims to co-develop and produce soft electronic devices with industry partners, including small and medium Enterprises (SMEs). “My goal is to establish a new centre of excellence for soft electronics, building a team of industry experts and commercial partners to swiftly bring these technologies to market,” Chen said.

Through joint projects, Chen hopes to establish industry standards to facilitate the mass production of soft electronics in the future and develop the necessary expertise for this industry. Chen’s team recently developed a wavy ribbon form for soft electronics, which will allow them to stretch without breaking. Another one of Chen’s innovations is “BIND” — a soft, stretchy, ‘Lego-like’ universal connector that joins flexible electronics by pressing them together. It can withstand stretching up to seven times its length and is reportedly 60 times tougher than conventional connectors. When used together, these technologies allow conventional hardware chips to be mounted and linked to resistors and capacitors through printed circuits.

Image credit: iStock.com/shawn_hempel

'Frozen smoke' sensors detect indoor pollutants

Thu, 15 Feb 2024 00:00:00 +1100

Researchers from the University of Cambridge have developed a sensor made from ‘frozen smoke’ that uses artificial intelligence techniques to detect formaldehyde in real time at concentrations beyond the sensitivity of most indoor air quality sensors. The sensor was made from porous materials known as aerogels; ultra-light materials that are sometimes referred to as “liquid smoke”, as they are more than 99% air by volume. By precisely engineering the shape of the holes in the aerogels, the sensors were able to detect the fingerprint of formaldehyde, a common indoor air pollutant, at room temperature.

The sensors, which require minimal power, could be adapted to detect a range of hazardous gases and could also be miniaturised for wearable and healthcare applications. Volatile organic compounds (VOCs) are a source of indoor air pollution and can cause watery eyes, burning in the eyes and throat, and difficulty breathing at elevated levels. Formaldehyde is a common VOC and is emitted by household items such as pressed wood products, wallpapers and paints, and some synthetic fabrics. The levels of formaldehyde emitted by these items are low, but can build up over time.

Professor Tawfique Hasan from the Cambridge Graphene Centre said current sensors don’t have the sensitivity or selectivity to distinguish between VOCs that have different impacts on health. The paper’s first author, Zhuo Chen, said the researchers wanted to develop a sensor that is small and doesn’t use much power, but can selectively detect formaldehyde at low concentrations.

The open structure of aerogels allows gases to move in and out. By engineering the shape of the holes, the aerogels can act as effective sensors. The researchers optimised the composition and structure of the aerogels to increase their sensitivity to formaldehyde, making them fit into filaments three times the width of a human hair. The researchers then 3D printed lines of a paste made from graphene and freeze-dried the graphene paste to form the holes in the final aerogel structure. The aerogels also incorporated small semiconductors known as quantum dots.

Chen said that traditional sensors need to be heated up, but the new sensors work well at room temperature because of the way the researchers engineered the materials. The new sensors reportedly use between 10 and 100 times less power than other sensors. The researchers also incorporated machine learning algorithms in the sensors, training the algorithms to detect the ‘fingerprint’ of different gases, so that the sensor was able to distinguish the fingerprint of formaldehyde from other VOCs.

“Existing VOC detectors are blunt instruments — you only get one number for the overall concentration in the air. By building a sensor that can detect specific VOCs at very low concentrations in real time, it can give home and business owners a more accurate picture of air quality and any potential health risks,” Hasan said.

The researchers’ technique could be used to develop sensors to detect other VOCs; theoretically, a device the size of a single household carbon monoxide detector could incorporate multiple different sensors within it, providing real-time information about a range of different hazardous gases.

“By using highly porous materials as the sensing element, we’re opening up whole new ways of detecting hazardous materials in our environment,” Chen said.

The research findings were published in the journal Science Advances.

Image credit: iStock.com/alexeyrumyantsev

This is a modified version of a news item published by the University of Cambridge under CC BY-NC-SA 4.0. This version is similarly licensed under CC BY-NC-SA 4.0. The original version of the news item can be accessed here.

Insights into the behaviour of excitons in 2D semiconductors

Wed, 14 Feb 2024 00:00:00 +1100

To better understand the potential of two-dimensional semiconductors for future computer and photovoltaic technologies, researchers from the Universities of Göttingen, Marburg and Cambridge investigated the bond that builds between the electrons and holes contained in these materials. The researchers used a special method to break up the bond between electrons and holes; as a result, they were able to gain a microscopic insight into charge transfer processes across the semiconductor interface.

When light shines on a semiconductor, its energy is absorbed. As a result, negatively charged electrons and positively charged holes combine in the semiconductor to form pairs, known as excitons. In modern two-dimensional semiconductors, these excitons have a high binding energy. The researchers set themselves the goal of examining the hole of the exciton.

First author Jan Philipp Bange from the University of Göttingen said the researchers used photoemission spectroscopy to investigate how the absorption of light in quantum materials leads to charge transfer processes. “So far, we have concentrated on the electrons that are part of the electron-hole pair, which we can measure using an electron analyser. Up to now, we didn’t have any way to directly access the holes themselves. So, we were interested in the question of how we could characterise not just the electron of the exciton but also its hole,” Bange said.

The researchers, led by Dr Marcel Reutzel, used a special microscope for photoelectrons and a high-intensity laser. In the process, the breaking up of an exciton led to a loss of energy in the electron measured in the experiment. Reutzel said this energy loss is characteristic for different excitons, depending on the environment in which the electron and the hole interact with each other.

The researchers used a structure consisting of two different atomically thin semiconductors to show that the hole of the exciton transfers from one semiconductor layer to the other, similar to a solar cell. The research team used a model to explain this charge transfer process and what happens at a microscopic level. Going forward, the researchers want to use the spectroscopic signature of the interaction between electrons and holes to study novel phases in quantum materials at ultrashort time and length scales.

The research findings were published in the journal Science Advances.

Image caption: An ultrashort flash of light breaks the bond between the electron (red) and the hole (blue), enabling research on charge-transfer processes in atomically thin semiconductors. Image credit: Lukas Kroll, Jan Philipp Bange, Marcel Reutzel, Stefan Mathias, Science Advances.

Researchers achieve data speed record on optical fibre

Wed, 14 Feb 2024 00:00:00 +1100

As data traffic increases, there is a need for miniaturised optical transmitters and receivers that operate with high-order multi-level modulation formats and faster data transmission rates. Researchers have developed a new compact indium phosphide (InP)-based coherent driver modulator (CDM) and achieved a high baud rate and transmission capacity per wavelength.

CDMs are optical transmitters used in optical communication systems that can put information on light by modulating the amplitude and phase before it is transmitted through optical fibre. Josuke Ozaki from the NTT Innovative Devices Corporation in Japan said that services that need data capacity, such as video distribution and web conferencing services, are widespread, with more services to be introduced in the future. To realise the new services, the total data rate of optical transmission systems needs to be increased.

“If the optical transmission capacity is insufficient, it will be difficult to realise new convenient services and data society. In addition, the development of an optical transmitter that covers the C+L band in a single module enables flexible network operation and reduces equipment costs,” Ozaki said.

The baud rate measures the speed of data transmission and indicates the number of signal changes that occur every second in a communication channel. With higher baud rates, the bandwidth of the modulation signal required for each channel increases and fewer channels can be transmitted in the conventional C-band. This makes it more important to extend the wavelength bandwidth from the C-band to the L-band. Together, they are referred to as the C+L band.

While modulators made from the semiconductor InP have excellent optical and radio frequency characteristics, they also exhibit strong wavelength dependence that makes it difficult to extend their wavelength range. To overcome this, the researchers developed a novel InP modulator chip with an optimised semiconductor layer and waveguide structure that can operate over a wide wavelength range. Using the new modulator chip enabled the researchers to achieve a CDM with an InP modulator chip that can transmit in C+L band and has a package body measuring 11.9 x 29.8 x 4.35 mm³.

In the C+L band, the new CDM exhibited an electro-optic 3 dB bandwidth of more than 90 GHz, an insertion loss at maximum transmission of less than 8 dB, and an extinction ratio of 28 dB or more. The researchers also applied the new CDM in experiments using 180 Gbaud probabilistically constellation-shaped 144-level quadrature amplitude modulation (PCS-144QAM) signals, demonstrating a net bit rate of 1.8 Tbps over 80 km standard single mode fibre in the C+L band.

According to the researchers, this is the first time an InP-based CDM has been shown to operate in the C+L bands and the world record’s transmission capacity per wavelength has been reported for a CDM. “The next step is to further increase the baud rate for a higher transmission speed. In doing so, it is important to find new modulator’s structure and assembly configuration, including a driver die and a package that can achieve higher EO bandwidth with both lower power consumption and smaller form factor,” Ozaki said.

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Novel UV tape developed for easy transfer of 2D materials

Wed, 14 Feb 2024 00:00:00 +1100

Two-dimensional materials could revolutionise future technology in the electronics industry. However, the commercialisation of devices that contain 2D materials is challenging, due to the difficulty of transferring these thin materials from where they are made onto the device. Now, researchers from Kyushu University have developed a tape that can be used to stick 2D materials to different surfaces, in an easy and user-friendly way. Lead author Hiroki Ago said transferring 2D materials can be a complex process, because the material can tear or become contaminated, which significantly degrades its unique properties. “Our tape offers a quick and simple alternative, and reduces damage,” Ago said.

The researchers focused on graphene, as it is tough, flexible and light, with high thermal and electrical conductivity. It also has potential applications in biosensing, anti-cancer drug delivery, aeronautics and electronic devices. Ago said that one of the main methods of making graphene is through chemical vapour deposition, where graphene is grown on copper film. However, in order to perform properly, the graphene must be separated from the copper and transferred onto an insulating substrate like silicon.

“To do this, a protective polymer is placed over the graphene, and the copper is then removed using etching solution, such as acid. Once attached to the new substrate, the protective polymer layer is then dissolved with a solvent. This process is costly, time-consuming and can cause defects to the graphene’s surface or leave traces of the polymer behind,” Ago said.

The researchers wanted to provide an alternative way of transferring graphene. They achieved this by using AI to develop a specialised polymer tape, dubbed “UV tape”, which changes its attraction to graphene when irradiated with UV light. Before exposure to UV light, the tape has a strong adhesion to graphene that allows it to ‘stick’. After UV exposure, the atom bonding changes and decreases the level of adhesion to graphene by approximately 10%. The tape also becomes stiffer and easier to peel off. These changes allow the tape to be peeled off the device substrate while leaving the graphene behind.

The newly designed UV tape is able to transfer 2D materials, including graphene and transition metal dichalcogenides, onto a range of different substrates, including silicon, ceramic, glass and plastic. Image credit: Ago Lab, Kyushu University

The researchers also developed tapes that can transfer other 2D materials, including white graphene (hBN), an insulator that acts as a protective layer when stacking 2D materials, and transition metal dichalcogenides (TMDs), a promising material for future semiconductors. When the researchers analysed the surface of the 2D materials after transfer, they saw a smoother surface with fewer defects than when transferred using the current conventional technique.

Transfer using UV tape also offers other advantages; because it is bendy, and the transfer process doesn’t require the use of plastic-dissolving solvents, flexible plastics can be used as the substrate of the device, expanding potential applications. “For example, we made a plastic device that uses graphene as a terahertz sensor. Like X-rays, terahertz radiation can pass through objects that light can’t, but doesn’t damage the body. It’s very promising for medical imaging or airport security,” Ago said.

The UV tape can also be cut to size, so that an exact amount of 2D material is transferred, minimising waste and reducing cost. 2D layers of different materials can also be laid on top of each other in different orientations, allowing researchers to explore new properties from the stacked materials.

Going forward, the researchers aim to expand the size of the UV tape to the scale needed for manufacturers. Currently, the largest wafer of graphene that can be transferred is 10 cm in diameter. The researchers also want to improve stability, so that the 2D materials can be attached to UV tapes for a longer period of time and distributed to end users, such as other scientists. The research findings were published in the journal Nature Electronics.

Top image credit: iStock.com/BONNINSTUDIO

3D-printed, air-powered modules help control soft robots

Thu, 08 Feb 2024 00:00:00 +1100

A team of researchers from the University of Freiburg have developed 3D-printed pneumatic logic modules that can control the movements of soft robots using air pressure. Soft robots could be used to perform tasks that cannot be carried out by conventional robots. These soft robots could be used in terrain that is difficult to access and in environments where they are exposed to chemicals or radiation that would harm robots made of metal. This requires soft robots to be controllable without any electronics, which is a challenge.

The 3D-printed pneumatic logic modules developed by the researchers enable logical switching of the air flow and can thus imitate electrical control. The modules make it possible to produce flexible and electronics-free soft robots entirely in a 3D printer using conventional filament printing material. The researchers, led by Dr Stefan Conrad and Dr Falk Tauber, published their research findings in the journal Science Robotics.

Tauber said the researchers’ design makes it possible for anyone with 3D printing experience to produce such logic modules and use them to control a soft robot without the need for high-end printing equipment. “This marks a significant step towards completely electronics-free pneumatic control circuits that can replace increasingly complex electrical components in soft robots in the future,” Conrad said.

The modules consist of two pressurised chambers, with a 3D-printed channel running between them. By compressing the channel, the expanding chambers can stop the air flow in it and regulate it like a valve. By opening and closing the valve in a targeted manner, the modules can perform the Boolean logic functions “AND”, “OR” and “NOT” in a similar way to electrical circuits and direct the air flow into the movement elements of the soft robot.

The chambers into which air pressure is applied help to determine what function the individual module performs. Depending on the material selected, the modules can be operated with a pressure of between 80 and more than 750 kilopascals. Compared to other pneumatic systems, they have a fast response time of around 100 milliseconds. Tauber said the modules have a range of potential applications.

“We have developed a flexible 3D-printed robotic walker that is controlled by an integrated circuit using air pressure. The flexibility of the logic modules is demonstrated by the fact that this walker can even withstand the load of a car driving over it,” Tauber said.

Image credit: iStock.com/kynny

Hexagonal copper disk lattice enables spin wave control

Thu, 08 Feb 2024 00:00:00 +1100

A group of researchers from Tohoku University has potentially developed a method to control spin waves by creating a hexagonal pattern of copper disks on a magnetic insulator. The team’s research findings are expected to lead to greater efficiency and miniaturisation of communication devices in fields such as artificial intelligence (AI) and automation technology. The research findings were published in the journal Physical Review Applied.

In magnetic material, the spins of electrons are aligned. When these spins undergo coordinated movement, the movement generates a ripple in the magnetic order, dubbed spin waves. Spin waves generate little heat and offer many advantages for next-generation devices. Implementing spin waves in semiconductor circuits, which rely on electrical currents, could reduce power consumption and promote high integration. Since spin waves are waves, they tend to propagate in random directions unless controlled by structures and other means. As such, elements capable of generating, propagating, superimposing and measuring spin waves are being developed worldwide.

Taichi Goto, co-author of the research paper, said the researchers leveraged the wavelike nature of spin waves to directly control their propagation. “We did so by first developing an excellent magnetic insulator material called magnetic garnet film, which has low spin wave losses. We then periodically arranged small copper disks with diameters less than 1 mm on this film,” Goto said.

By arranging copper disks in a hexagonal pattern resembling snowflakes, the researchers could effectively reflect the spin waves. By rotating the magnonic crystal and changing the incident angle of spin waves, the researchers revealed that the frequency at which the magnonic band gap occurs remains unchanged in the range from 10 to 30 degrees. This suggests the potential for the two-dimensional magnonic crystal to control the propagation direction of spin waves.

Going forward, the researchers aim to demonstrate the direction control of spin waves using two-dimensional magnonic crystals and to develop functional components that utilise this technology.

Top image caption: An illustration of the two-dimensional magnonic crystal developed in this study, viewed from an oblique angle. Copper disks are periodically arranged on a magnetic garnet film. Image credit: Taichi Goto et al.