Categorie: Uncategorized

Ecranul de piele ultra-elastic, foarte elastic, prezintă citiri electrocardiogramă(Ultrathin, highly elastic skin display shows electrocardiogram readings)

Un nou ultrastensiv, elastic, care se potrivește perfect pe piele, poate arăta forma de undă în mișcare a unei electrocardiograme înregistrate de un senzor de electrod care se respiră. Combinat cu un modul de comunicare fără fir, acest sistem integrat de senzori biomedicali – numit „electronica pielii” – poate transmite date biometrice către nor.Senzorul de piele nanomesh poate fi purtat pe piele continuu timp de o săptămână fără a provoca inflamații. Deși acest senzor, dezvoltat într-un studiu anterior, a fost capabil să măsoare temperatura, presiunea și mioelectricitatea (proprietățile electrice ale mușchilor), a înregistrat cu succes o electrocardiogramă pentru prima dată în ultimele cercetări.

Posted: Feb 19, 2018

Ultrathin, highly elastic skin display shows electrocardiogram readings

(Nanowerk News) A new ultrathin, elastic display that fits snugly on the skin can show the moving waveform of an electrocardiogram recorded by a breathable, on-skin electrode sensor. Combined with a wireless communication module, this integrated biomedical sensor system – called „skin electronics” – can transmit biometric data to the cloud.
This latest research by a Japanese academic-industrial collaboration, led by Professor Takao Someya at the University of Tokyo’s Graduate School of Engineering, is slated for a news briefing and talk („Continuous Health-Monitoring With Ultraflexible On-Skin Sensors)” at the AAAS Annual Meeting in Austin, Texas on February 17th.
Ultrathin Deformable Skin Display Withstands Stretching
The soft, flexible skin display is about 1 millimeter thick, and consists of a 16 x 24 array of micro LEDs and stretchable wiring mounted on a rubber sheet. It can withstand repeated stretching, by as much as 45 percent of its original length, without showing any loss in function of its electrical and mechanical properties. (Image: Takao Someya Research Group)
Thanks to advances in semiconductor technology, wearable devices can now monitor health by first measuring vital signs or taking an electrocardiogram, and then transmitting the data wirelessly to a smartphone. The readings or electrocardiogram waveforms can be displayed on the screen in real time, or sent to either the cloud or a memory device where the information is stored.
The newly-developed skin electronics system aims to go a step further by enhancing information accessibility for people such as the elderly or the infirm, who tend to have difficulty operating and obtaining data from existing devices and interfaces. It promises to help ease the strain on home healthcare systems in aging societies through continuous, non-invasive health monitoring and self-care at home.
The new integrated system combines a flexible, deformable display with a lightweight sensor composed of a breathable nanomesh electrode and wireless communication module. Medical data measured by the sensor, such as an electrocardiogram, can either be sent wirelessly to a smartphone for viewing or to the cloud for storage. In the latest research, the display showed a moving electrocardiogram waveform that was stored in memory.
The skin display, developed by a collaboration between researchers at the University of Tokyo’s Graduate School of Engineering and Dai Nippon Printing (DNP), a leading Japanese printing company, consists of a 16 x 24 array of micro LEDs and stretchable wiring mounted on a rubber sheet.
„Our skin display exhibits simple graphics with motion,” says Someya. „Because it is made from thin and soft materials, it can be deformed freely.”
The display is stretchable by as much as 45 percent of its original length.
It is far more resistant to the wear and tear of stretching than previous wearable displays. It is built on a novel structure that minimizes the stress resulting from stretching on the juncture of hard materials, such as the micro LEDs, and soft materials, like the elastic wiring – a leading cause of damage for other models.
Thumbs-up Icon On Skin Display
An integrated „skin electronics” system allows health monitoring at home and gives doctors remote access to biometric data transmitted wirelessly to a medical cloud. It promises to enhance self-care and accessibility of medical information to various segments of the population, including children and the elderly. A thumbs-up image on the skin display serves as an indicator of good health. (Image: Takao Someya Research Group)
It is the first stretchable display to achieve superior durability and stability in air, such that not a single pixel failed in the matrix-type display while attached snugly onto the skin and continuously subjected to the stretching and contracting motion of the body.
The nanomesh skin sensor can be worn on the skin continuously for a week without causing any inflammation. Although this sensor, developed in an earlier study, was capable of measuring temperature, pressure and myoelectricity (the electrical properties of muscle), it successfully recorded an electrocardiogram for the first time in the latest research.
The researchers applied tried-and-true methods used in the mass production of electronics – specifically, screen printing the silver wiring and mounting the micro LEDs on the rubber sheet with a chip mounter and solder paste commonly used in manufacturing printed circuit boards. Applying these methods will likely accelerate the commercialization of the display and help keep down future production costs.
DNP is looking to bring the integrated skin display to market within the next three years by improving the reliability of the stretchable devices through optimizing its structure, enhancing the production process for high integration, and overcoming technical challenges such as large-area coverage.
„The current aging society requires user-friendly wearable sensors for monitoring patient vitals in order to reduce the burden on patients and family members providing nursing care,” says Someya. „Our system could serve as one of the long-awaited solutions to fulfill this need, which will ultimately lead to improving the quality of life for many.”
Source: University of Tokyo

Respirătoare, electronice portabile pe piele pentru monitorizarea sănătății pe termen lung(Breathable, wearable electronics on skin for long-term health monitoring)

Un senzor electronic hipoalergenic poate fi purtat pe piele continuu timp de o saptamana fara disconfort si este atat de usor si de subtire incat utilizatorii uita ca au chiar si ei, spune un grup de cercetatori de la Universitatea din Tokyo si colaboratorii lor. Electrodul elastic, construit din ochiuri de dimensiuni reduse la nivel de nanoparticule, promite dezvoltarea unor dispozitive neinvazive de e-skin, care pot monitoriza continuu starea de sănătate a unei persoane pe o perioadă lungă de timp ( Nature Nanotechnology , „Inflammation free, permeable gas, lightweight, stretchable on-skin electronics cu nanomeshes ” )

Posted: Feb 05, 2018

Breathable, wearable electronics on skin for long-term health monitoring

(Nanowerk News) A hypoallergenic electronic sensor can be worn on the skin continuously for a week without discomfort, and is so light and thin that users forget they even have it on, says a group of researchers at the University of Tokyo and their collaborators. The elastic electrode constructed of breathable nanoscale meshes holds promise for the development of noninvasive e-skin devices that can monitor a person’s health continuously over a long period (Nature Nanotechnology, „Inflammation-free, gas-permeable, lightweight, stretchable on-skin electronics with nanomeshes”).
Nanomesh conductor applied to back of hand
Nanomesh conductor applied to back of hand. The nanomesh electrode closely follows the contours of the back of the hand for a perfect fit when attached to the skin. The stretchable device lets the skin breathe naturally, and is so thin and light that wearers forget they even have it on. (Image: Someya Laboratory)
Wearable electronics that monitor heart rate and other vital health signals have made headway in recent years, with next-generation gadgets employing lightweight, highly elastic materials attached directly onto the skin for more sensitive, precise measurements.
However, although the ultrathin films and rubber sheets used in these devices adhere and conform well to the skin, their lack of breathability is deemed unsafe for long-term use: dermatological tests show the fine, stretchable materials prevent sweating and block airflow around the skin, causing irritation and inflammation, which ultimately could lead to lasting physiological and psychological effects.
„We learned that devices that can be worn for a week or longer for continuous monitoring were needed for practical use in medical and sports applications,” says Professor Takao Someya at the University of Tokyo’s Graduate School of Engineering whose research group had previously developed an on-skin patch that measured oxygen in blood.
In the current research, the group developed an electrode constructed from nanoscale meshes containing a water-soluble polymer, polyvinyl alcohol (PVA), and a gold layer—materials considered safe and biologically compatible with the body. The device can be applied by spraying a tiny amount of water, which dissolves the PVA nanofibers and allows it to stick easily to the skin—it conformed seamlessly to curvilinear surfaces of human skin, such as sweat pores and the ridges of an index finger’s fingerprint pattern.
The researchers next conducted a skin patch test—for irritations and skin allergies—on 20 subjects and detected no inflammation on the participants’ skin after they had worn the device for a week. The group also evaluated the permeability, with water vapor, of the nanomesh conductor—along with those of other substrates like ultrathin plastic foil and a thin rubber sheet—and found that its porous mesh structure exhibited superior gas permeability compared to that of the other materials.
Furthermore, the scientists proved the device’s mechanical durability through repeated bending and stretching, exceeding 10,000 times, of a conductor attached on the forefinger; they also established its reliability as an electrode for electromyogram recordings when its readings of the electrical activity of muscles were comparable to those obtained through conventional gel electrodes.
„It will become possible to monitor patients’ vital signs without causing any stress or discomfort,” says Someya about the future implications of the team’s research. In addition to nursing care and medical applications, the new device promises to enable continuous, precise monitoring of athletes’ physiological signals and bodily motion without impeding their training or performance.
Source: University of Tokyo

Îmbunătățirea capacităților de detectare cuantică a diamantului(Enhancing the quantum sensing capabilities of diamond)

senzori si resurse imbunatatite pentru tehnologiile cuantice.
Diamantele sunt fabricate din atomi de carbon într-o structură cristalină, dar dacă un atom de carbon este înlocuit cu un alt tip de atom, acest lucru va duce la un defect de zăbrele. Un astfel de defect este Nitrogen-Vacancy (NV), unde un atom de carbon este înlocuit cu un atom de azot, iar vecinul său lipsește (un spațiu gol rămâne în locul său).
Dacă acest defect este iluminat cu un laser verde, în urma răspunsului acesta va emite lumină roșie (fluorescentă) cu o caracteristică interesantă: intensitatea sa variază în funcție de proprietățile magnetice din mediul înconjurător. Această caracteristică unică face ca centrul NV să fie deosebit de util pentru măsurarea câmpurilor magnetice, a imaginilor magnetice (MRI), a calculului cuantic și a informațiilor.

Posted: Nov 22, 2017

Enhancing the quantum sensing capabilities of diamond

(Nanowerk News) Researchers have discovered that dense ensembles of quantum spins can be created in diamond with high resolution using an electron microscopes, paving the way for enhanced sensors and resources for quantum technologies.
Diamonds are made of carbon atoms in a crystalline structure, but if a carbon atom is replaced with another type of atom, this will result in a lattice defect. One such defect is the Nitrogen-Vacancy (NV), where one carbon atom is replaced by a nitrogen atom, and its neighbor is missing (an empty space remains in its place).
If this defect is illuminated with a green laser, in response it will emit red light (fluoresce) with an interesting feature: its intensity varies depending on the magnetic properties in the environment. This unique feature makes the NV center particularly useful for measuring magnetic fields, magnetic imaging (MRI), and quantum computing and information.
In order to produce optimal magnetic detectors, the density of these defects should be increased without increasing environmental noise and damaging the diamond properties.
Now, scientists from the research group of Nir Bar-Gill at the Hebrew University of Jerusalem’s Racah Institute of Physics and Department of Applied Physics, in cooperation with Prof. Eyal Buks of the Technion – Israel Institute of Technology, have shown that ultra-high densities of NV centers can be obtained by a simple process of using electron beams to kick carbon atoms out of the lattice.
Diamond Sample Illuminated by Green Light
This photo shows a diamond sample illuminated by green light in home-built microscope. The sample is placed on a special mount, within a printed circuit board, used to deliver microwaves which allow quantum manipulations and magnetic sensing with the NVs. (Image: Yoav Romach
This work, published in the scientific journal Applied Physics Letters („Enhanced concentrations of nitrogen-vacancy centers in diamond through TEM irradiation”), is a continuation of previous work in the field, and demonstrates an improvement in the densities of NV centers in a variety of diamond types. The irradiation is performed using an electron beam microscope (Transmission Electron Microscope or TEM), which has been specifically converted for this purpose. The availability of this device in nanotechnology centers in many universities in Israel and around the world enables this process with high spatial accuracy, quickly and simply.
The enhanced densities of the NV color centers obtained, while maintaining their unique quantum properties, foreshadow future improvements in the sensitivity of diamond magnetic measurements, as well as promising directions in the study of solid state physics and quantum information theory.
Nitrogen Vacancy (NV) color centers exhibit remarkable and unique properties, including long coherence times at room temperature (~ ms), optical initialization and readout, and coherent microwave control.
„This work is an important stepping stone toward utilizing NV centers in diamond as resources for quantum technologies, such as enhanced sensing, quantum simulation and potentially quantum information processing”, said Bar-Gill, an Assistant Professor in the Dept. of Applied Physics and Racah Institute of Physics at the Hebrew University, where he founded the Quantum Information, Simulation and Sensing lab.
„What is special about our approach is that it’s very simple and straightforward,” said Hebrew University researcher Dima Farfurnik. „You get sufficiently high NV concentrations that are appropriate for many applications with a simple procedure that can be done in-house.”
Source: The Hebrew University of Jerusalem

Culorile adevarate satisfac minimizarea – Senzorul de culori stivuit(True colors meet minimization – The stacked color sensor)

Sensori de culoare sensibili la roșu, sensibili la albastru și sensibili la culoarea verde, stivuiți unul peste celălalt în loc să fie aliniați într-un model mozaic – acest principiu ar putea permite senzorilor de imagine cu rezoluție fără precedent și sensibilitate la lumină să fie creatș au dezvoltat un prototip senzor care absoarbe aproape în mod optim lumina – și este, de asemenea, ieftin să produca…

Posted: Nov 16, 2017

True colors meet minimization – The stacked color sensor

(Nanowerk News) Red-sensitive, blue-sensitive and green-sensitive color sensors stacked on top of each other instead of being lined up in a mosaic pattern – this principle could allow image sensors with unprecedented resolution and sensitivity to light to be created. However, so far, the reality hasn’t quite met expectations.
Researchers from Empa and ETH Zurich have now developed a sensor prototype that absorbs light almost optimally – and is also cheap to produce (Science, „Properties and potential optoelectronic applications of lead halide perovskites nanocrystals”).
Original image (left) and corresponding portrayal of the red, green and blue regions, and a composite image
Original image (left) and corresponding portrayal of the red, green and blue regions, and a composite image. (Image: Empa)
The human eye has three different types of sensory cells for the perception of color: cells that are respectively sensitive to red, green and blue alternate in the eye and combine their information to create an overall colored image. Image sensors, for example in mobile phone cameras, work in a similar way: blue, green and red sensors alternate in a mosaic-like pattern. Intelligent software algorithms calculate a high-resolution color image from the individual color pixels.
However, the principle also has some inherent limitations: as each individual pixel can only absorb a small part of the light spectrum that hits it, a large part of the light is lost. In addition, the sensors have basically reached the limits of miniaturization, and unwanted image disturbances can occur; these are known as color moiré effects and have to be laboriously removed from the finished image.

Transparent only for certain colors
Researchers have, therefore, been working for a number of years on the idea of stacking the three sensors instead of placing them next to each other. Of course, this requires that the sensors on top let through the light frequencies that they do not absorb to the sensors underneath. At the end of the 1990s, this type of sensor was successfully produced for the first time. It consisted of three stacked silicon layers, each of which absorbed only one color.
Stack instead of mosaic: the perovskite layers each absorb only part of the light spectrum
Stack instead of mosaic: the perovskite layers each absorb only part of the light spectrum. (Image: Empa)
This actually resulted in a commercially available image sensor. However, this was not successful on the market because the absorption spectra of the different layers were not distinct enough, so part of the green and red light was absorbed by the blue-sensitive layer. The colors, therefore, blurred and the light sensitivity was thus lower than for ordinary light sensors. In addition, the production of the absorbing silicon layers required a complex and expensive manufacturing process.
Empa researchers have now succeeded in developing a sensor prototype that circumvents these problems. It consists of three different types of perovskites – a semiconducting material that has become increasingly important during the last few years, for example in the development of new solar cells, due to its outstanding electrical properties and good optical absorption capacity (see „Further reading”). Depending on the composition of these perovskites, they can, for example, absorb part of the light spectrum, but remain transparent for the rest of the spectrum.
The researchers in Maksym Kovalenko’s group at Empa and ETH Zurich used this principle to create a color sensor with a size of just one pixel. The researchers were able to reproduce both simple one-dimensional and more realistic two-dimensional images with an extremely high color fidelity.

Accurate recognition of colors
The advantages of this new approach are clear: the absorption spectra are clearly differentiated and the color recognition is thus much more precise than with silicon. In addition, the absorption coefficients, especially for the light components with higher wavelengths (green and red), are considerably higher in the perovskites than in silicon.
As a result, the layers can be made significantly smaller, which in turn allows smaller pixel sizes. This is not crucial in the case of ordinary camera sensors; however, for other analysis technologies, such as spectroscopy, this could permit significantly higher spatial resolution. The perovskites can also be produced using a comparatively cheap process.
However, more work is still needed in order to further develop this prototype into a commercially viable image sensor. Key areas include the miniaturization of pixels and the development of methods for producing an entire matrix of such pixels in one step. According to Kovalenko, this should be possible with existing technologies.
Source: By Karin Weinmann, Empa

Noii senzori de mișcare buckypaper reprezintă un pas important spre tehnologia low-cost, de înaltă performanță care poate fi purtată(New buckypaper motion sensors a major step toward low-cost, high-performance wearable technology)

aplicațiile potențiale pentru senzorii buckypaper tipăriți sunt limitate doar de amploarea imaginației cercetătorilor. Designul cu profil redus ar putea fi integrat în foile de pat pentru a monitoriza calitatea somnului, pantofii pentru a urmări numărul de pasi și postura sau hainele de antrenament pentru a măsura intensitatea exercițiilor fizice.
Cercetătorii prevăd, de asemenea, aplicații potențiale dincolo de domeniul tehnologiei portabile. În domeniul roboticii moi, materialul ar putea facilita progresul în producerea mușchilor artificiali autocorecți responsabili.
Mai mult, senzorii scalabili reprezintă un alt pas spre viitorul mult așteptat al unui „internet al lucrurilor”, unde aproape toate computerele, dispozitivele, articolele de îmbrăcăminte, mobilierul și aparatele individuale sunt conectate digital pentru a face schimb de informații în mod liber în nor.

Posted: Nov 16, 2017

New buckypaper motion sensors a major step toward low-cost, high-performance wearable technology

(Nanowerk News) Researchers from the FAMU-FSU College of Engineering have developed a class of breakthrough motion sensors that could herald a near future of ubiquitous, fully integrated and affordable wearable technology.
In a paper published in the journal Materials and Design („Printable low-cost and flexible carbon nanotube buckypaper motion sensors”), engineers from FSU’s High-Performance Materials Institute, in collaboration with scientists from Institut National des Sciences Appliquées in Lyon, France, detail the impressive properties and cost-effective manufacturing process of an advanced series of motion sensors made using buckypaper — razor thin, flexible sheets of pure, exceptionally durable carbon nanotubes.
These new buckypaper sensors represent a marked improvement on current industry standards, with most sensors being either too crude or too inflexible to reliably monitor complex structures like the human body.
“Current technology is not designed for that,” said Richard Liang, director of the High-Performance Materials Institute and professor at the FAMU-FSU College of Engineering. “For sensor technology, you need it to be flexible, you need it to be affordable and you need it to be scalable. This new technology is versatile and the sensors are affordable to print. It’s a big innovation that presents many possibilities down the road.”
Joshua DeGraff
FAMU-FSU College of Engineering doctoral candidate Joshua DeGraff developed an advanced class of scalable motion sensors using silver ink electrodes and sheets of pure carbon nanotube buckypaper.
At this stage, potential applications for the printable buckypaper sensors are limited only by the breadth of researchers’ imaginations. The low-profile design could be integrated into bedsheets to monitor quality of sleep, shoes to track step count and posture or workout clothes to measure intensity of exercise.
Researchers also foresee potential applications beyond the realm of wearable technology. In the field of soft robotics, the material could facilitate advances in the production of responsive, self-correcting artificial muscles.
Moreover, the scalable sensors represent another step toward the long-predicted future of an “internet of things,” where virtually all of an individual’s computers, devices, garments, furniture and appliances are digitally connected to freely exchange information in the cloud.
“Most projects don’t have this many possible applications,” said doctoral candidate Joshua DeGraff, the lead author of the study. “This material could be used in structural health monitoring, wearable technology and everything in between. I’m excited because this is something that can affect a lot of people in their everyday lives.”
The novel sensor structure combines a strip of seven micron-thin buckypaper with silver ink electrodes printed from a common, commercially available ink-jet printer.
The result is a kind of perfect Goldilocks sensor: not as insensitive as common, flexible metallic sensors, but not as rigid or cumbersome as popular, more sensitive semi-conductor sensors.
The wearable buckypaper sensors are an ideal marriage of these competing qualities. They’re flexible, seamless and sensitive to subtle movements and strains.
“We measure sensors by gauge factor, which indicates how much resistance value changes as a material is strained or bent,” DeGraff said. “Our gauge factor has been up to eight times higher than commercial sensors and 75 percent higher than many other carbon nanotube sensors.”
As development of the printable sensor technology continues, researchers hope to improve upon the already remarkable thinness of the material so that it can be integrated into comfortable and non restrictive clothing. Additional testing on complex model structures is required to ensure the material’s ability to conform to the variable curves and crevices of the human body.
While the technology might not be ready for primetime quite yet, researchers are energized by its promising future.
“As engineering professors, we want to see the things we create in the lab become successful products,” Liang said. “We’re not quite there yet, but this is an important step. Consumers want great quality and affordable prices, and this material provides both of those things.”
Source: Florida State University

Foarte flexibilă memorie flash organică pentru electronice pliabile și de unică folosință(Highly flexible organic flash memory for foldable and disposable electronics)

Acest studiu ilustrează foarte bine faptul că o memorie flash extrem de flexibilă poate fi făcută pentru a avea un nivel practic de performanță viabil, astfel încât să contribuie la aparatele electronice portabile și la hârtia electronică inteligentă”.

Posted: Nov 07, 2017

Highly flexible organic flash memory for foldable and disposable electronics

(Nanowerk News) A KAIST team reported ultra-flexible organic flash memory that is bendable down to a radius of 300 µm. The memory exhibits a significantly-long projected retention rate with a programming voltage on par with the present industrial standards.
A joint research team led by Professor Seunghyup Yoo of the School of Electrical Engineering and Professor Sung Gap Im of the Department of Chemical and Biomolecular Engineering said that their memory technology can be applied to non-conventional substrates, such as plastics and papers, to demonstrate its feasibility over a wide range of applications.
With Dr. Seungwon Lee and Dr. Hanul Moon playing the role of leading authors, the research was published in Nature Communications („Organic flash memory on various flexible substrates for foldable and disposable electronics”).
Foldable flash memory
Foldable flash memory. (Image: KAIST)
Flash memory is a non-volatile, transistor-based data-storage device that has become essential in most electronic systems in daily life. With straightforward operation mechanisms and easy integration into NAND or NOR array architecture, flash memory has been established as the most successful and dominant non-volatile memory technology by far.
Despite promising demonstrations in the early stages of organic electronics, the overall progress in this field has been far slower than that of thin-film transistors (TFTs) or other devices based on flexible materials. It has been challenging, in particular, to develop flash memory that simultaneously exhibits a significant level of flexibility and performance. This is mainly due to the scarcity of flexible dielectric layers, which are responsible for the tunneling and blocking of charges.
The solution processing used for the preparation of most of the polymeric dielectric layers also makes it difficult to use them in flash memory due to the complexity involved in the formation of the bilayer dielectric structure, which is the key to flash memory operations.
The research team tried to overcome these hurdles and realize highly flexible flash memory by employing thin polymeric insulators grown with initiated chemical vapor deposition (iCVD), a vapor-phase growth technique for polymers that was previously shown to be promising for the fabrication of flexible TFTs. It was further shown that these iCVD-based polymeric insulators, when coupled with rational device design and material choice, can make a significant contribution to flash memory as well.
Memory using conventional polymer insulating films has often required a voltage as high as 100 V (volt) in order to attain long memory retention. If the device is made to operate at a low voltage, the short retention period of less than a month was problematic.
Structure of flexible flash memory
Structure of flexible flash memory. (Image: KAIST)
The KAIST team produced flash memory with programming voltages around 10 V and a projected data retention time of over 10 years, while maintaining its memory performance even at a mechanical strain of 2.8%. This is a significant improvement over the existing inorganic insulation layer-based flash memory that allowed only a 1% strain.
The team demonstrated the virtually foldable memory devices by fabricating the proposed flash memory on a 6-micrometer-thick ultrathin plastic film. In addition, it succeeded in producing them on printing paper, opening a way for disposable smart electronic products such as electronic paper and electronic business card.
Professor Yoo said, ” This study well illustrates that even highly flexible flash memory can be made to have a practically viable level of performance, so that it contributes to full-fledged wearable electronic devices and smart electronic paper.”
Source: The Korea Advanced Institute of Science and Technology (KAIST)

Cercetătorii dezvoltă dispozitive fotonice flexibile și extensibile(Researchers develop flexible, stretchable photonic devices)

Dispozitivele ar putea găsi utilizări în cabluri pentru a conecta dispozitive de calcul sau în sisteme de diagnosticare și monitorizare care ar putea fi atașate pe piele sau implantate în corp, flexându-se ușor cu țesutul natural.Astfel de circuite fotonice flexibile și elastice ar putea fi, de asemenea, utile pentru aplicațiile în care dispozitivele trebuie să se conformeze suprafețelor inegale ale altui material, cum ar fi în manometrele de tensiune

Posted: Nov 08, 2017

Researchers develop flexible, stretchable photonic devices

(Nanowerk News) Researchers at MIT and several other institutions have developed a method for making photonic devices — similar to electronic devices but based on light rather than electricity — that can bend and stretch without damage. The devices could find uses in cables to connect computing devices, or in diagnostic and monitoring systems that could be attached to the skin or implanted in the body, flexing easily with the natural tissue.
The findings, which involve the use of a specialized kind of glass called chalcogenide, are described in two papers by MIT Associate Professor Juejun Hu and more than a dozen others at MIT, the University of Central Florida, and universities in China and France. The paper is slated for publication soon in Light: Science and Applications („Monolithically integrated stretchable photonics”).
flexible, stretchable photonic device material
A new material produced by Juejun Hu and his team can be repeatedly stretched without losing its optical properties. (Image: MIT)
Hu, who is the Merton C. Flemings Associate Professor of Materials Science and Engineering, says that many people are interested in the possibility of optical technologies that can stretch and bend, especially for applications such as skin-mounted monitoring devices that could directly sense optical signals. Such devices might, for example, simultaneously detect heart rate, blood oxygen levels, and even blood pressure.
Photonics devices process light beams directly, using systems of LEDs, lenses, and mirrors fabricated with the same kinds of processes used to manufacture electronic microchips. Using light beams rather than a flow of electrons can have advantages for many applications; if the original data is light-based, for example, optical processing avoids the need for a conversion process.
But most current photonics devices are fabricated from rigid materials on rigid substrates, Hu says, and thus have an “inherent mismatch” for applications that “should be soft like human skin.” But most soft materials, including most polymers, have a low refractive index, which leads to a poor ability to confine a light beam.
Instead of using such flexible materials, Hu and his team took a novel approach: They formed the stiff material — in this case a thin layer of a type of glass called chalcogenide — into a spring-like coil. Just as steel can be made to stretch and bend when formed into a spring, the architecture of this glass coil allows it to stretch and bend freely while maintaining its desirable optical properties.
“You end up with something as flexible as rubber, that can bend and stretch, and still has a high refractive index and is very transparent,” Hu says. Tests have shown that such spring-like configurations, made directly on a polymer substrate, can undergo thousands of stretching cycles with no detectable degradation in their optical performance. The team produced a variety of photonic components, interconnected by the flexible, spring-like waveguides, all in an epoxy resin matrix, which was made stiffer near the optical components and more flexible around the waveguides.
Other kinds of stretchable photonics have been made by embedding nanorods of a stiffer material in a polymer base, but those require extra manufacturing steps and are not compatible with existing photonic systems, Hu says.
Such flexible, stretchable photonic circuits could also be useful for applications where the devices need to conform to the uneven surfaces of some other material, such as in strain gauges. Optics technology is very sensitive to strain, according to Hu, and could detect deformations of less than one-hundredth of 1 percent.
This research is still in early stages; Hu’s team has demonstrated only single devices at a time thus far. “For it to be useful, we have to demonstrate all the components integrated on a single device,” he says. Work is ongoing to develop the technology to that point so that it could be commercially applied, which Hu says could take another two to three years.
In another paper published last week in Nature Photonics („Chalcogenide glass-on-graphene photonics”), Hu and his collaborators have also developed a new way of integrating layers of photonics, made of chalcogenide glass and two-dimensional materials such as graphene, with conventional semiconductor photonic circuitry. Existing methods for integrating such materials require them to be made on one surface and then peeled off and transferred to the semiconductor wafer, which adds significant complexity to the process. Instead, the new process allows the layers to be fabricated directly on the semiconductor surface, at room temperature, allowing for simplified fabrication and more precise alignment.
The process can also make use of the chalcogenide material as a “passivation layer,” to protect 2-D materials from degradation caused by ambient moisture, and as a way to control the optoelectronic characteristics of 2-D materials. The method is generic and could be extended to other emerging 2-D materials besides graphene, to expand and expedite their integration with photonic circuitry, Hu says.
Source: By David L. Chandler, MIT