Categorie: Materiale, echipamente si substante care pot constitui noi tipuri de senzori in domeniul detectiei si anihilarii substantelor toxice chimice sau agentilor biologici

O nouă rotire pe tehnica veche pentru a crea materiale de absorbție mai bune(A new spin on old technique to engineer better absorptive materials)

a unei clase de materiale denumite cadre organice metalice – MOF. MOF-urile sunt folosite pentru detectarea, purificarea și depozitarea gazelor și ar putea contribui la rezolvarea unor provocări energetice, de mediu și farmaceutice cele mai provocatoare din lume – pot chiar trage molecule de apă direct din aer pentru a asigura scutirea de secetă.MOF sunt cristale poroase la scară microscopică, proiectate din ioni metalici legați împreună de molecule organice numite liganzi. Deși sunt mici, au o abilitate imensă de absorbție.

Posted: Nov 13, 2017

A new spin on old technique to engineer better absorptive materials

(Nanowerk News) A team of University of Illinois bioengineers has taken a new look at an old tool to help characterize a class of materials called metal organic frameworks – MOFs for short. MOFs are used to detect, purify and store gases, and could help solve some of the world’s most challenging energy, environmental and pharmaceutical challenges – they can even pull water molecules straight from the air to provide relief from drought.
The research team, led by bioengineering professor Rohit Bhargava, is using infrared chemical imaging to examine and optimize the structure of MOFs. Although around for more than a decade, IR imaging is greatly underutilized in materials analysis. The researchers found that with a few modifications to improve the speed of analysis, it is the perfect tool for this application. Their findings are published in the Journal of Physical Chemistry Letters („Mapping solvation environments in porous metal organic frameworks with infrared chemical imaging”).
University of Illinois bioengineers, from left, Ayanjeet Ghosh, professor Rohit Bhargava, Prabuddha Mukherjee and Sanghamitra Deb
University of Illinois bioengineers, from left, Ayanjeet Ghosh, professor Rohit Bhargava, Prabuddha Mukherjee and Sanghamitra Deb are using an updated infrared imaging technique to better examine and optimize a group of materials that could help solve some of the world’s most challenging energy, environmental and pharmaceutical challenges.
MOFs are microscopic-scale porous crystals engineered from metal ions bound together by organic molecules called ligands. Although they are tiny, they have an immense absorptive ability.
„The pores allow the MOFs to work like tiny sponges that can soak up chemicals such as pharmaceuticals and gases,” said Sanghamitra Deb, a postdoctoral researcher at the Beckman Institute for Advanced Science and Technology at the U. of I.
„The precise structure and chemistry of MOFs greatly influence their functionality,” said Prabuddha Mukherjee, a Beckman Institute research scientist. „Therefore, detailed characterization is essential in determining their best use.”
The traditional methods used in materials science analysis, like high-powered electron microscopy and spectroscopy, do not combine chemical insights with the spatial resolution of IR imaging, the researchers said, so they can only provide average chemical measurements.
MOFs form by crystallizing out of a solution, and there is no way of fully controlling their structure or chemistry. „This lack of control leaves a lot of room for defects to form, and the traditional methods for characterization only tell us that there is a defect but cannot pinpoint the specific location,” Mukherjee said.
„IR imaging allows us to see the chemistry and the structure in one shot,” said Ayanjeet Ghosh, a postdoctoral researcher with the Beckman Institute. „We can resolve structures down to a few microns and determine their chemical composition over a few micron areas, understand how and why the spectra change as a function of space, and do it with a single analysis.”
IR imaging also offers a unique scale range to work in, the researchers said.
„We do not need to see down to the atomic scale, like many high-powered electron microscopy methods offer,” Deb said. „At that scale, it would take a very long time to scan devices made with MOFs, which are typically about a millimeter squared in size.”
Finally, many of the other traditional techniques are destructive, meaning that once analyzed with one method, the sample cannot be examined with any additional tools. „We may be able to spot an aberration in chemistry via spectroscopy, but we don’t have the opportunity to see where the defect actually exists using another method because the sample is now gone,” Ghosh said. „With IR imaging, we can do both at the same time.”
„This unique use of an older technique, but with new instrumentation, allows us to quickly determine the quality and best application for specific MOFs in a nondestructive way – something no other group has been able to do,” Mukherjee said.
The group envisions this technique being used with other devices made under similar conditions, as well as uses outside of the materials science realm.
Source: By Lois Yoksoulian, University of Illinois at Urbana-Champaign

Promițătoare nanosenzori pentru submarine, mine și nave spațiale(Promising nanosensors for submarines, mines and spacecraft)

au descoperit un mecanism care permite senzorilor de gaz, bazați pe oxizi de metale nanocristaline, să lucreze la temperatura camerei. Această invenție va spori eficiența monitorizării mediului la centralele nucleare, submarine și nave spațiale.Cercetătorii au descoperit că compozitele bazate pe oxizi de zinc și indiu pot crește semnificativ sensibilitatea senzorului la hidrogen

Posted: Nov 10, 2017

Promising nanosensors for submarines, mines and spacecraft

(Nanowerk News) Researchers from the Physics Department of Moscow State University and their colleagues have discovered a mechanism that allows gas sensors, based on nanocrystalline metal oxides, to work at room temperature. This invention will raise the efficiency of environmental monitoring at nuclear power plants, on submarines and spacecrafts. The discovery was reported in Scientific Reports („Green light activated hydrogen sensing of nanocrystalline composite ZnO-In2O3 films at room temperature”).
Hydrogen Sensor Scheme
This is a hydrogen sensor scheme. (Image: Alexander Ilyin)
Scientists have proposed a new fundamental principle of operation of hydrogen sensors. Unlike most resistive gas detectors, it does not need to be heated and only requires visible light. This discovery will significantly reduce the energy consumption of the sensor and expand its scope.
„Such sensors can be used in explosive environments or be built into mobile devices without constructing additional heat sink systems,” said Alexander Ilyin, a co-author of the study, a PhD student at the Physics Department of Moscow State University.
Researchers have found out that composites based on zinc and indium oxides can significantly increase the sensitivity of the sensor to hydrogen. Physicists have also proposed an explanation for the hypersensitivity of the designed composite. In their opinion, the sensor response mechanism consists in a change in the processes of generation and recombination of nonequilibrium electrons when the composite is interacting with hydrogen. Composites with a certain structure provide a more significant change in these processes.
Samples for the sensor were made from nanocrystalline indium and zinc oxide powders. The structure and particle size were studied by the means of transmission electron microscopy and x-ray diffraction. The electrical and sensor characteristics of the structureswere studied in the new designed setup, in which the required temperature of the composite and the concentration of hydrogen were well controlled.
The obtained results would allow the scientists to develop a new type of resistive hydrogen sensor that works under additional illumination without heating. Such sensors are promising not only for effective monitoring of environmental pollution in industrial plants, but also for constant monitoring of air in closed facilities (submarines, mines, spacecraft) where the slightest change in the chemical composition can lead to human casualties.
Source: Lomonosov Moscow State University

Tehnica de transfer produce senzori de gaz de nitrură de galiu care pot fi purtați(Transfer technique produces wearable gallium nitride gas sensors)

O tehnica de transfer bazata pe straturi subtiri de sacrificiu de nitrura de bor ar putea permite senzorilor de gaz nitridiu de inalta performanta sa fie crescuti pe substraturi de safir si apoi transferate pe materiale polimerice sau flexibile de polimer. Tehnica ar putea facilita producerea de dispozitive de detectare mobile, mobile și de unică folosință cu costuri reduse pentru o gamă largă de aplicații de mediu.

Posted: Nov 09, 2017

Transfer technique produces wearable gallium nitride gas sensors

(Nanowerk News) A transfer technique based on thin sacrificial layers of boron nitride could allow high-performance gallium nitride gas sensors to be grown on sapphire substrates and then transferred to metallic or flexible polymer support materials. The technique could facilitate the production of low-cost wearable, mobile and disposable sensing devices for a wide range of environmental applications.
Transferring the gallium nitride sensors to metallic foils and flexible polymers doubles their sensitivity to nitrogen dioxide gas, and boosts response time by a factor of six. The simple production steps, based on metal organic vapor phase epitaxy (MOVPE), could also lower the cost of producing the sensors and other optoelectronic devices.
Sensors produced with the new process can detect ammonia at parts-per-billion levels and differentiate between nitrogen-containing gases. The gas sensor fabrication technique was reported November 9 in the journal Scientific Reports („Gas sensors boosted by two-dimensional h-BN enabled transfer on thin substrate foils: towards wearable and portable applications”).
Image shows wafer-scale processed AlGaN/GaN sensors being tested
Image shows wafer-scale processed AlGaN/GaN sensors being tested. (Image: Georgia Tech Lorraine)
„Mechanically, we just peel the devices off the substrate, like peeling the layers of an onion,” explained Abdallah Ougazzaden, director of Georgia Tech Lorraine in Metz, France and a professor in Georgia Tech’s School of Electrical and Computer Engineering (ECE). „We can put the layer on another support that could be flexible, metallic or plastic. This technique really opens up a lot of opportunity for new functionality, new devices – and commercializing them.”
The researchers begin the process by growing monolayers of boron nitride on two-inch sapphire wafers using an MOVPE process at approximately 1,300 degrees Celsius. The boron nitride surface coating is only a few nanometers thick, and produces crystalline structures that have strong planar surface connections, but weak vertical connections.
Aluminum gallium nitride (AlGaN/GaN) devices are then grown atop the monolayers at a temperature of about 1,100 degrees Celsius, also using an MOVPE process. Because of the boron nitride crystalline properties, the devices are attached to the substrate only by weak Van der Waals forces, which can be overcome mechanically. The devices can be transferred to other substrates without inducing cracks or other defects. The sapphire wafers can be reused for additional device growth.
„This approach for engineering GaN-based sensors is a key step in the pathway towards economically viable, flexible sensors with improved performances that could be integrated into wearable applications,” the authors wrote in their paper.
So far, the researchers have transferred the sensors to copper foil, aluminum foil and polymeric materials. In operation, the devices can differentiate between nitrogen oxide, nitrogen dioxide, and ammonia. Because the devices are approximately 100 by 100 microns, sensors for multiple gases can be produced on a single integrated device.
„Not only can we differentiate between these gases, but because the sensor is very small, we can detect them all at the same time with an array of sensors,” said Ougazzaden, who expects that the devices could be modified to also detect ozone, carbon dioxide and other gases.
The gallium nitride sensors could have a wide range of applications from industry to vehicle engines – and for wearable sensing devices. The devices are attractive because of their advantageous materials properties, which include high thermal and chemical stability.
„The devices are small and flexible, which will allow us to put them onto many different types of support,” said Ougazzaden, who also directs the International Joint Research Lab at Georgia Tech CNRS.
To assess the effects of transferring the devices to a different substrate, the researchers measured device performance on the original sapphire wafer and compared that to performance on the new metallic and polymer substrates. They were surprised to see a doubling of the sensor sensitivity and a six-fold increase in response time, changes beyond what could be expected by a simple thermal change in the devices.
„Not only can we have flexibility in the substrate, but we can also improve the performance of the devices just by moving them to a different support with appropriate properties,” he said. „Properties of the substrate alone makes the different in the performance.”
In future work, the researchers hope to boost the quality of the devices and demonstrate other sensing applications. „One of the challenges ahead is to improve the quality of the materials so we can extend this to other applications that are very sensitive to the substrates, such as high-performance electronics.”
The Georgia Tech researchers have previously used a similar technique to produce light-emitting diodes and ultraviolet detectors that were transferred to different substrates, and they believe the process could also be used to produce high-power electronics. For those applications, transferring the devices from sapphire to substrates with better thermal conductivity could provide a significant advantage in device operation.
Ougazzaden and his research team have been working on boron-based semiconductors since 2005. Their work has attracted visits from several industrial companies interested in exploring the technology, he said.
„I am very excited and lucky to work on such hot topic and top-notch technology at GT-Lorraine,” said Taha Ayari, a Ph.D. student in the Georgia Tech School of ECE and the paper’s first author.
Source: Georgia Institute of Technology

Tehnica de transfer produce senzori de gaz de nitrură de galiu care pot fi purtați(Transfer technique produces wearable gallium nitride gas sensors)

Senzorii produse prin noul proces pot detecta amoniacul la nivelele pe miliarde de hectare și pot diferenția între gazele care conțin azot.Transferul senzorilor de nitrură de galiu la foliile metalice și polimerii flexibili își dublează sensibilitatea la gazul de dioxid de azot și crește timpul de răspuns cu un factor de șase. Etapele simple de producție, bazate pe epitaxia cu fază metalică cu vapori organici (MOVPE), ar putea, de asemenea, să reducă costul producerii senzorilor și a altor dispozitive optoelectronice.

Posted: Nov 09, 2017

Transfer technique produces wearable gallium nitride gas sensors

(Nanowerk News) A transfer technique based on thin sacrificial layers of boron nitride could allow high-performance gallium nitride gas sensors to be grown on sapphire substrates and then transferred to metallic or flexible polymer support materials. The technique could facilitate the production of low-cost wearable, mobile and disposable sensing devices for a wide range of environmental applications.
Transferring the gallium nitride sensors to metallic foils and flexible polymers doubles their sensitivity to nitrogen dioxide gas, and boosts response time by a factor of six. The simple production steps, based on metal organic vapor phase epitaxy (MOVPE), could also lower the cost of producing the sensors and other optoelectronic devices.
Sensors produced with the new process can detect ammonia at parts-per-billion levels and differentiate between nitrogen-containing gases. The gas sensor fabrication technique was reported November 9 in the journal Scientific Reports („Gas sensors boosted by two-dimensional h-BN enabled transfer on thin substrate foils: towards wearable and portable applications”).
Image shows wafer-scale processed AlGaN/GaN sensors being tested
Image shows wafer-scale processed AlGaN/GaN sensors being tested. (Image: Georgia Tech Lorraine)
„Mechanically, we just peel the devices off the substrate, like peeling the layers of an onion,” explained Abdallah Ougazzaden, director of Georgia Tech Lorraine in Metz, France and a professor in Georgia Tech’s School of Electrical and Computer Engineering (ECE). „We can put the layer on another support that could be flexible, metallic or plastic. This technique really opens up a lot of opportunity for new functionality, new devices – and commercializing them.”
The researchers begin the process by growing monolayers of boron nitride on two-inch sapphire wafers using an MOVPE process at approximately 1,300 degrees Celsius. The boron nitride surface coating is only a few nanometers thick, and produces crystalline structures that have strong planar surface connections, but weak vertical connections.
Aluminum gallium nitride (AlGaN/GaN) devices are then grown atop the monolayers at a temperature of about 1,100 degrees Celsius, also using an MOVPE process. Because of the boron nitride crystalline properties, the devices are attached to the substrate only by weak Van der Waals forces, which can be overcome mechanically. The devices can be transferred to other substrates without inducing cracks or other defects. The sapphire wafers can be reused for additional device growth.
„This approach for engineering GaN-based sensors is a key step in the pathway towards economically viable, flexible sensors with improved performances that could be integrated into wearable applications,” the authors wrote in their paper.
So far, the researchers have transferred the sensors to copper foil, aluminum foil and polymeric materials. In operation, the devices can differentiate between nitrogen oxide, nitrogen dioxide, and ammonia. Because the devices are approximately 100 by 100 microns, sensors for multiple gases can be produced on a single integrated device.
„Not only can we differentiate between these gases, but because the sensor is very small, we can detect them all at the same time with an array of sensors,” said Ougazzaden, who expects that the devices could be modified to also detect ozone, carbon dioxide and other gases.
The gallium nitride sensors could have a wide range of applications from industry to vehicle engines – and for wearable sensing devices. The devices are attractive because of their advantageous materials properties, which include high thermal and chemical stability.
„The devices are small and flexible, which will allow us to put them onto many different types of support,” said Ougazzaden, who also directs the International Joint Research Lab at Georgia Tech CNRS.
To assess the effects of transferring the devices to a different substrate, the researchers measured device performance on the original sapphire wafer and compared that to performance on the new metallic and polymer substrates. They were surprised to see a doubling of the sensor sensitivity and a six-fold increase in response time, changes beyond what could be expected by a simple thermal change in the devices.
„Not only can we have flexibility in the substrate, but we can also improve the performance of the devices just by moving them to a different support with appropriate properties,” he said. „Properties of the substrate alone makes the different in the performance.”
In future work, the researchers hope to boost the quality of the devices and demonstrate other sensing applications. „One of the challenges ahead is to improve the quality of the materials so we can extend this to other applications that are very sensitive to the substrates, such as high-performance electronics.”
The Georgia Tech researchers have previously used a similar technique to produce light-emitting diodes and ultraviolet detectors that were transferred to different substrates, and they believe the process could also be used to produce high-power electronics. For those applications, transferring the devices from sapphire to substrates with better thermal conductivity could provide a significant advantage in device operation.
Ougazzaden and his research team have been working on boron-based semiconductors since 2005. Their work has attracted visits from several industrial companies interested in exploring the technology, he said.
„I am very excited and lucky to work on such hot topic and top-notch technology at GT-Lorraine,” said Taha Ayari, a Ph.D. student in the Georgia Tech School of ECE and the paper’s first author.
Source: Georgia Institute of Technology

Un sistem de testare enzimatică bioluminescent pentru evaluarea toxicității nanomaterialelor de carbon(A bioluminescent enzymatic test system for assessing the toxicity of carbon nanomaterials)

dezvoltarea nanotehnologiei a dus la răspândirea utilizarea nanomaterialelor în diverse domenii ale industriei.
Sistemul de testare a fost deja testat pentru capacitatea de a determina rapid prezența în mediu a unor astfel de substanțe toxice precum metalele grele sau pesticidele. Noi prezicem ca moleculele de exprimare moleculara „Enzymolum” vor fi utilizate pe scara larga in diferite sfere. „utilizarea reactivului bioluminescent „Enzymolum” pentru a testa toxicitatea nanomaterialelor. „Enzymolum” este un sistem enzimatic unic al mai multor molecule izolate de bacterii luminoase marine.

Posted: Nov 02, 2017

A bioluminescent enzymatic test system for assessing the toxicity of carbon nanomaterials

(Nanowerk News) Official website of the Russian Science Foundation reports that a group of scientists from Siberian Federal University and Krasnoyarsk Scientific Center of the SB RAS has developed a bioluminescent enzymatic test system for assessing the toxicity of carbon nanomaterials.
Its distinctive features are simplicity, fast reaction speed and high sensitivity. The results of the study are published in the journal Toxicology in Vitro („Bioluminescent enzyme inhibition-based assay to predict the potential toxicity of carbon nanomaterials”).
The scientists proposed using the bioluminescent reagent „Enzymolum” to test the toxicity of nanomaterials. „Enzymolum” is a unique enzymatic system of several molecules isolated from marine luminous bacteria. The intensity of the luminescence of the reagent varies under the action of various additives. Scientists have tested the ability of commercial nanomaterials, such as various carbon nanotubes and fullerenes, to suppress the luminescence of the enzymatic system. The greatest inhibitory effect was observed for multiwalled nanotubes.
It should be noted that such an action was fixed at concentrations of nanomaterials exceeding those expected in the environment. However, with the increase in their application, we can expect an increase in the concentrations occurring in nature.
According to Elena Esimbekova, an Associate Professor of the Department of Biophysics at the School of Fundamental Biology and Biotechnology of SibFU, a researcher at the Institute of Biophysics of the Krasnoyarsk Scientific Center of the SB RAS, the development of nanotechnology has led to the widespread use of nanomaterials in various fields of industry.
At present, artificially created nanoparticles, primarily on the basis of carbon, are actively used in the production of medicines, cosmetics and in the food industry: „We have been developing the ‘Enzymolum’ test systems over the past ten years. Today it is an easy-to-use technology. Reagent is a small dried disk with enzymes included in them. Each of the disks is designed to carry out one measurement. Disks can be stored for a long time without loss of properties. The analysis itself takes 2 or 3 minutes. After that, you have a result – whether the solution of the studied sample affects the glow of the biological material. Based on this it can be concluded wether there is potential toxicity. The test system has already been tested for the ability to quickly determine the presence in the environment of such toxicants as heavy metals or pesticides. We predict that the molecular express-biotest ‘Enzymolum’ will be widely used in different spheres.”
The research was carried out with the support of the Russian Science Foundation in the framework of the project „New methodology of complex express assessment of soil quality and contamination based on enzymatic bioluminescent systems”.
Source: Siberian Federal University

Senzori bazați pe chip cu incredibilă sensibilitate(Chip-based sensors with incredible sensitivity)

Acest tip de senzor este format din sfere solide și nu este compatibil cu metodele de microfabricare, dar recent, Tadigadapa și echipa sa au dezvoltat o modalitate inovatoare de a dezvolta coji microsferice din sticlă cu chip cu senzitivități incredibile care pot fi utilizate pentru mișcare, temperatură, presiune sau biochimie detectare. Puteți face un senzor de umiditate cu adevărat sensibil.Poti face senzatia chimica, senzatia de vapori, senzatia biofizica, senzatia de presiune si senzatia de temperatura deosebita

Posted: Nov 02, 2017

Chip-based sensors with incredible sensitivity

(Nanowerk News) In London’s St. Paul’s Cathedral, a whisper can be heard far across the circular whispering gallery as the sound curves around the walls. Now, an optical whispering gallery mode resonator developed by Penn State electrical engineers can spin light around the circumference of a tiny sphere millions of times, creating an ultrasensitive microchip-based sensor for multiple applications.
“Whispering gallery mode resonators, which are basically optical resonators, have been intensely studied for at least 20 years,” said Penn State electrical engineering professor Srinivas Tadigadapa. “What people have done is to take an optical fiber and touch the end with a blow torch. When the melted fiber re-condenses, it forms a sphere at the tip. This can be coupled to a light source to make a sensor.”
That type of sensor consists of solid spheres and is not compatible with microfabrication methods, but recently Tadigadapa and his team developed an innovative way to grow on-chip glass microspherical shells with incredible sensitivities that potentially can be used for motion, temperature, pressure or biochemical sensing.
Chip-scale glass microspherical shell sensor array blown on a silicon substrate. Insert is a near-perfect spherical shell
Chip-scale glass microspherical shell sensor array blown on a silicon substrate. Insert is a near-perfect spherical shell. (Image: Tadigadapa Lab/Penn State)
The hollow borosilicate glass spheres are blown from sealed and pressurized cylindrical cavities etched into a silicon substrate. Using a glassblowing technique, the thin glass wafer, under high heat and external vacuum pressure, forms an almost perfect bubble. The researchers grew arrays of spheres from 230 microns to 1.2 millimeters in diameter with wall thicknesses between 300 nanometers and 10 micrometers.
“The bottom of the sphere is thinned until it is basically a hole,” Tadigadapa said. “You can put the light on the outside of the sphere but do all the chemistry on the inner face of the shell. You can bring in any analyte that you want to identify, but it goes on the inner surface. That brings in a lot of possibilities. You can do chemical sensing, vapor sensing, biophysical sensing, pressure sensing and really outstanding temperature sensing.”
After many failed attempts, the team discovered that the key to making a high- quality sensor lay in making sure that the equatorial plane of the sphere, its center, is above the surface of the chip.
To get an understanding of the quality of their spheres, Tadigadapa’s Ph.D. student Chenchen Zhang and recent Ph.D. graduate Eugene Freeman worked with Alexander Cocking, a Ph.D. student in the lab of Penn State laser expert Zhiwen Liu, professor of electrical engineering.
“We make the bubbles and then take them to Dr. Liu’s lab to get the resonance levels and make the measurements,” said Zhang, lead author on a paper describing their work in Scientific Reports(„On-Chip Glass Microspherical Shell Whispering Gallery Mode Resonators”).
This result will have particular significance for lab-on-a-chip biophysical sensing for disease sensing, Zhang said. “Or by adding a polymer coating on the inside of the bubble, you could make a really sensitive humidity sensor.”
Tadigadapa added, “There are some really exciting possibilities. I think it will spawn a large follow-up work.”
Source: Penn State Materials Research Institute

Stofele inteligente obțin un upgrade major printr-o serie de primele de cercetare(Smart fabrics get major upgrade through a series of research firsts)

Noua tehnologie care foloseste semnale electronice intr-o tesatura inteligenta ar putea conduce la un echipament avansat de materiale periculoase care protejeaza impotriva chimicalelor toxice,Progresul ar putea avea mari implicații pentru personalul militar, serviciul de urgență și alți lucrători care se bazează pe protecția „haz-mat” pentru a-și desfășura activitatea și pentru ai menține pe ceilalți în siguranță. dispozitivele SOFT care prezintă MOF prezintă o conductivitate sigură, o porozitate sporită, flexibilitate și stabilitate la spălare. Țesăturile sunt, de asemenea, stabile în căldură, au o durată de depozitare bună și păstrează o gamă largă de utilități în condiții umede.

Posted: Nov 01, 2017

Smart fabrics get major upgrade through a series of research firsts

(Nanowerk News) New technology that harnesses electronic signals in a smart fabric could lead to advanced hazardous-material gear that protects against toxic chemicals, according to research from Dartmouth College.
The advancement could have big implications for the military, emergency service personnel and other workers that rely on „haz-mat” protection to perform their work and keep others safe.
In research published in the Journal of the American Chemical Society („Self-Organized Frameworks on Textiles (SOFT): Conductive Fabrics for Simultaneous Sensing, Capture, and Filtration of Gases”), the chemistry team of Katherine Mirica and Merry Smith describe the creation of new smart fabrics – named SOFT, for Self-Organized Framework on Textiles – in what is noted as the first demonstration of simultaneous detection, capture, pre-concentration and filtration of gases in a wearable that uses conductive, porous materials integrated into soft textiles.
Multifunctional E-textile Metal-organic Framework
The SOFT e-textile uses metal-organic frameworks (MOFs) to improve detection and protection from toxic chemicals. (Image: K. A. Mirica)
According to the study, the SOFT devices have the potential for use in sensing applications ranging from real-time gas detection in wearable systems, to electronically accessible adsorbent layers in protective equipment like gas masks.
„By adding this fabric to a protective suit, sensors can alert the user if a chemical is penetrating the hazardous-material gear,” said Katherine Mirica, an assistant professor of chemistry at Dartmouth College. „This is not just passive protection, the textile can actively alarm a user if there is a tear or defect in the fabric, or if functional performance is diminished in any other way.”
Among other firsts described in the research are flexible, textile-supported electronic sensors based on materials known as metal-organic frameworks, or MOFs. In the study, the authors also describe a „simple” approach for integrating these conductive, porous materials into cotton and polyester fabrics to produce the e-textiles.
As part of the study, the Dartmouth team demonstrated that the new smart fabric can detect common toxic chemicals. Both the vehicle exhaust pollutant, nitric oxide, and the corrosive poison that reminds most of rotten eggs, hydrogen sulfide, were effectively identified by the SOFT system. In addition to sensing the chemicals, the electronic textiles are capable of capturing and filtering the dangerous toxins.
„Metal-organic frameworks are the future of designer materials, just like plastics were in the post-WWII era,” said Mirica. „By integrating the MOFs into our SOFT devices, we dramatically enhance the performance of smart fabrics that are essential to safety and security.”
The research team also describes a one-step e-textile fabrication method based on MOFs that likely constitutes the first use of direct self-assembly to deposit the conductive material on textiles.
In a process that Mirica describes as „similar to a building framework assembling itself,” cotton and polyester textiles coated with conductive crystals at the fiber-level are created by direct self-assembly of molecules with organic molecular struts connected by metallic linkers from solution.
Wearable electronics are thought to have great potential in areas including homeland security, communication and healthcare. Soldiers, emergency personnel, factory workers and others that risk exposure to toxic chemicals could benefit from the new smart fabrics. The materials could also help medical patients that require monitoring of specific airborne chemicals that come from the environment or even from their own bodies.
According to researchers, the SOFT devices featuring MOFs display reliable conductivity, enhanced porosity, flexibility and stability to washing. The fabrics are also stable in heat, have good shelf-lives and retain a full-range of utility under humid conditions.
While the technology requires further development before it can be used in state-of-the-art wearable systems, the authors are hopeful that the fabrication method has the potential to be extended into other systems, producing a range of novel, multifunctional e-textiles with highly tunable properties and a host of new applications in wearable and portable devices.
Source: Dartmouth College

Graphene permite circuite electronice de mare viteză pe materiale flexibile(Graphene enables high-speed electronics on flexible materials)

Detectorul are caracteristici unice. La temperatura camerei, detectează semnale în intervalul de frecvență de la 330 la 500 gigahertzi. Este translucid și flexibil și se deschide la o varietate de aplicații. Tehnica poate fi utilizată pentru imagistică în zona terahertz (camera THz), dar și pentru identificarea diferitelor substanțe (senzor). De asemenea, poate avea un beneficiu potențial în îngrijirea sănătății, unde undele terahertz pot fi folosite pentru detectarea cancerului. Alte domenii în care detectorul poate fi utilizat sunt senzori de imagine pentru vehicule sau pentru comunicații fără fir.
Caracteristicile electronice unice ale grafenului, combinate cu natura sa flexibilă, fac din el un material promițător de integrare în plastic și țesătură, ceea ce va constitui un bloc de construcție important într-o lume viitoare interconectată. Tehnologia Graphene permite aplicații noi, printre altele, obiecte de zi cu zi, care sunt denumite în mod obișnuit Internetul Lucrurilor.
Detectorul arată posibilitățile concrete ale grafenului, un material care conduce extrem de bine curentul electric. Este o caracteristică care face ca grafenul să devină un bloc de atracție în domeniul electronicii rapide. Activitatea cercetătorilor de la Chalmers este, prin urmare, un important pas înainte pentru grafen în zona terahertz și un progres pentru performanțe ridicate și tehnologie ieftină terahertz

Posted: Oct 31, 2017

Graphene enables high-speed electronics on flexible materials

(Nanowerk News) A flexible detector for terahertz frequencies (1000 gigahertz) has been developed by Chalmers researchers using graphene transistors on plastic substrates. It is the first of its kind, and can extend the use of terahertz technology to applications that will require flexible electronics, such as wireless sensor networks and wearable technology. The results are published in the scientific journal Applied Physics Letters („A flexible graphene terahertz detector”).
flexible graphene terahertz detector
With the help of the two-dimensional material graphene, the first flexible terahertz detector has been developed by researchers at Chalmers. The opportunities are great within health and Internet of Things, and for new types of sensors. (Image: Boid – Product Design Studio, Gothenburg)
Terahertz radiation has a wide range of uses and can occur in everything from radio astronomy to medicine. The term refers to the electromagnetic waves whose frequencies range from 100 gigahertz to 10 terahertz. Demand for higher bandwidth in wireless communications and depiction for security applications has led to intensified research on systems and components intended for terahertz frequencies.
One challenge has long been to enable low weight and cheap applications. However, advances in polymer technology have promoted the development of flexible electronics and enabled the production of high frequency units on flexible substrates.
Now, Chalmers researchers Xinxin Yang, Andrei Vorobiev, Andrey Generalov, Michael A. Andersson and Jan Stake have developed the first mechanically flexible and graphene-based terahertz detector in its kind. Thus, paving the way for flexible terahertz electronics.
The detector has unique features. At room temperature, it detects signals in the frequency range 330 to 500 gigahertz. It is translucent and flexible, and opens to a variety of applications. The technique can be used for imaging in the terahertz area (THz camera), but also for identifying different substances (sensor). It may also be of potential benefit in health care, where terahertz waves can be used to detect cancer. Other areas where the detector could be used are imaging sensors for vehicles or for wireless communications.
The unique electronic features of graphene, combined with its flexible nature, make it a promising material to integrate into plastic and fabric, something that will be important building blocks in a future interconnected world. Graphene electronics enables new applications for, among other things, everyday objects, which are commonly referred to as the Internet of Things.
The detector shows the concrete possibilities of graphene, a material that conduct electric current extremely well. It is a feature that makes graphene an attractive building block in fast electronics. The Chalmers researchers’ work is therefore an important step forward for graphene in the terahertz area, and a breakthrough for high performance and cheap flexible terahertz technology.
The detector drew attention at the EU Tallinn Digital Summit recently, where several important technological innovations made possible by graphene and related materials were on display. At the summit, EU Heads of State and Government gathered to discuss digital innovation and Europe’s digital future. The flagship focus was to show what role graphene can play.
The research is also part of Xinxin Yang’s licentiate seminar, which will be presented at Chalmers on 22 November 2017.
Source: Chalmers University of Technology

De cleiuri și gaze: senzori de aderență la bară și senzori nanomecanici(Of glues and gases: Barnacle adhesion and nanomechanical sensors)

Yoshikawa va vorbi și despre cercetarea și dezvoltarea unui al doilea sistem nanomecanic care utilizează „analiza aero-termo-dinamică a masei” (AMA), pentru a caracteriza gazele prin măsurarea directă a greutății lor moleculare în condiții ambiante fără vacuum, ionizare sau instrumente voluminoase cerută de analiza spectrală în masă. Similar metodei de deformare prin care MSS detectează moleculele de gaze, AMA calculează greutatea moleculară a unei specii de gaz prin măsurarea modificării mecanice a unui obiect elastic simplu plasat sub un flux constant al gazului. Procesul poate fi realizat atât la scară nanometrică, cât și la macroscala, permițând senzorilor AMA să fie extrem de mici, portabili și capabili să fie integrați în alte dispozitive, cum ar fi telefoanele mobile.

Posted: Oct 30, 2017

Of glues and gases: Barnacle adhesion and nanomechanical sensors

(Nanowerk News) Among the diverse research studies being presented at this year’s 64th AVS International Symposium and Exhibition, being held Oct. 29-Nov. 2, 2017, in Tampa, Florida, are two biomaterial interfaces sessions that feature some highly unusual applications of engineering. The first describes the use of stress forces – more commonly employed to evaluate the failure mechanisms of materials and devices made from them – to discover how barnacles stick to surfaces. The second explores the development of two novel mechanical systems, both smaller than the eye can see, for use with gas molecules: one to detect them with ultra-high sensitivity and the other to precisely measure their molecular weights.
In the first presentation, biomedical engineer Manuel Figueroa of the College of New Jersey will discuss his research examining the effect of hydrophobicity (resistance to bonding with water) on the adhesive ability of the acorn barnacle, Amphibalanus amphitrite. This species is an abundant and widespread biofouler that is particularly troublesome for the marine shipping industry since a barnacle-encrusted ship hull creates drag on the vessel, reducing its performance and increasing fuel consumption.
To analyze barnacle adhesion in the laboratory, Figueroa allowed the arthropods to attach for two weeks to untreated glass slides representing hydrophilic surfaces as well as glass slides coated with hydrophobic self-assembled monolayers. He then removed the barnacles using a force gauge and calculated the critical shear stress needed to do the job for both sets. Finally, the quantity of glue remaining on the substrates was measured. What Figueroa discovered was that the critical shear stress was significantly higher for the hydrophobic surfaces as was the density of residual glue. The strong correlation, he said, suggests that hydrophobic surfaces may provide a protected environment for the barnacles to release their adhesive and that barnacle release only occurs when this cohesion fails. With further research, these findings may help shipbuilders and others design surfaces that exploit the nonadhesive characteristics.
In the second presentation, nanotechnology researcher Genki Yoshikawa of the National Institute for Materials Science in Japan will discuss the ongoing development and application of two nanometer-scale (billionth of a meter) mechanical devices for the detection and characterization of gas molecules. The first is the membrane-type surface stress sensor (MSS), that utilizes a circular membrane connected by cantileverlike “bridge spans” to a frame with embedded electrical resistors. Gas molecules are detected when they adsorb to the receptor layer coated on the membrane and deform it slightly, thereby perturbing the current flowing through the resistors. The MSS has great potential as a gas sensor, Yoshikawa said, because it is highly sensitive, can be designed to detect specific gases, and offers portability, ease of use and low cost. However, Yoshikawa said that adapting the MSS into a practical consumer mobile/”internet of things” sensor system requires “further optimization and integration of lots of components including receptor layers, hardware including electronics and sample handling, multidimensional data analysis, and precise calibration for high reproducibility.” This, Yoshikawa said, is the mission of an industry-academia-government consortium known as the MSS Alliance.
Yoshikawa also will talk about his group’s research and development of a second nanomechanical system that uses “aero-thermo-dynamic mass analysis” (AMA), to characterize gases by directly measuring their molecular weight in ambient conditions without the vacuum, ionization or bulky instrumentation required by mass spectral analysis. Similar to the deformation method by which MSS detects gas molecules, AMA calculates the molecular weight of a gas species by measuring the mechanical alteration of a simple elastic object placed under a constant flow of the gas. The process can be carried out at the nanoscale as well as the macroscale, allowing AMA sensors to be extremely tiny, portable and capable of being integrated into other devices such as cell phones.

References
Presentation BI-MoM1, “Characterization of Adult Barnacle Adhesion Upon Reattachment to Hydrophobic Surfaces” by Manuel Figueroa, is at 8:20 a.m. EDT Oct. 30, 2017, in Room 12 in the Tampa Convention Center, Tampa, Florida.
Presentation MN+BI_NS-MoM-3, “Nanomechanical Sensors (MSS, AMA) Toward IoT Olfactory Sensor System” by Genki Yoshikawa, is at 9:00 a.m. EDT Oct. 30, 2017, in Room 24 in the Tampa Convention Center, Tampa, Florida.
Source: AVS

Punctele cuantice vizualizează rezonanțele vibraționale minuscule(Quantum dots visualize tiny vibrational resonances)

lumină.
O aplicație posibilă a acestei descoperiri, potrivit lui Sam Carter de la Naval Research Lab, unul dintre autorii lucrării, este de a detecta forțe subtile produse de obiecte dense din apropiere. „Materialele nucleare ascunse ar putea fi detectabile”, a spus el, „din moment ce materiale dense cum ar fi plumbul sunt folosite pentru a proteja dispozitivele.”
Ecranul foarte dens necesar pentru materialele nucleare cauzează mici anomalii gravitaționale și mișcări minore care ar putea fi detectabile de un dispozitiv bazat pe principiul descoperit aici. Cercetătorii intenționează să-și continue activitatea făcând abstracție de spinul electronic. Se speră că tehnicile de măsurare a efectului pe spin vor crește sensibilitatea dispozitivelor.

Posted: Oct 30, 2017

Quantum dots visualize tiny vibrational resonances

(Nanowerk News) In the late 18th century, Ernst Chladni, a scientist and musician, discovered that the vibrations of a rigid plate could be visualized by covering it with a thin layer of sand and drawing a bow across its edge. With the bow movement, the sand bounces and shifts, collecting along the nodal lines of the vibration. Chladni’s discovery of these patterns earned him the nickname, „father of acoustics.” His discovery is still used in the design and construction of acoustic instruments, such as guitars and violins.
Recently, investigators have discovered a similar effect with much smaller vibrating objects excited by light waves. When laser light is used to drive the motion of a thin, rigid membrane, it plays the role of the bow in Chladni’s original experiment and the membrane vibrates in resonance with the light. The resulting patterns can be visualized through an array of quantum dots (QDs), where these tiny structures emit light at a frequency that responds to movement. The advance is reported this week in a cover article of Applied Physics Letters („Sensing flexural motion of a photonic crystal membrane with InGaAs quantum dots”).
Image of a Chladni Plate'S Mode of Vibration Visualized By Grains of Sand Collected at the Nodes
Background: Image of a Chladni plate’s mode of vibration visualized by grains of sand collected at the nodes. Left-top: Cross-sectional scanning tunneling microscopy image of an indium arsenide quantum dot. Left-bottom: Variation of quantum dot emission line frequencies as a function of time due to vibrations of the photonic crystal membrane. Right: Scanning electron micrograph of a photonic crystal membrane, displaced according to one of the vibrational modes, with red and blue representing positive and negative displacement, respectively. (Image: Sam Carter and co-authors)
In addition to being a modern take on an old phenomenon, the new discovery could lead to the development of sensing devices as well as methods for controlling the emission characteristics of QDs. Since the light frequency emitted by the QDs is correlated with the movement of the underlying membrane, new devices for sensing motion, such as accelerometers, can be envisioned. A reverse application is also possible since the motion of the underlying membrane can be used to control the frequency of light emitted by the QDs.
The tiny devices in the work reported here consist of a 180-nanometer thick slice of semiconductor, suspended like a trampoline above a solid substrate. An array of QDs, analogous to the sand in the acoustic example, are embedded in the slice, whose thickness is less than one-tenth of one percent that of a human hair.
A second probe laser is used to visualize the resulting resonances. The QDs absorb the probe light and emit a second light pulse in response, which is picked up by a detector and routed to a display. The resulting patterns are remarkably like those visualized in Chladni’s original acoustic experiment, even though the new device is driven entirely by light.
One possible application of this discovery, according to Sam Carter of the Naval Research Lab who is one of the paper’s authors, is to sense subtle forces produced by nearby dense objects. „Concealed nuclear materials could be detectable,” he said, „since dense materials like lead are used to shield the devices.”
The highly dense shielding needed for nuclear materials causes small gravitational anomalies and tiny movements that might be detectable by a device based on the principle discovered here. The investigators plan to continue their work by looking at electronic spin. It is hoped that techniques to measure the effect on spin will increase the sensitivity of the devices.
Source: American Institute of Physics

Hidrogele pentru senzori chimici(Hydrogels for Chimical Sensors)

descriem microsensorii chimici piezorezistenți pentru o caracterizare cuprinzătoare a soluțiilor, care ar putea fi încorporate în sistemele fluidice pentru monitorizarea în timp real a contaminanților organici și anorganici

Hidrogel pentru senzori chimici