Lună: februarie 2018

Computerele ajută la descoperirea unui material nou, ieftin pentru a face LED-urile cu o calitate ridicată a culorilor(Computers aid discovery of new, inexpensive material to make LEDs with high color quality)

un nou material fosfor pentru LED-uri albe care este ieftin și ușor de făcut. Cercetatorii au construit prototipuri de becuri cu LED-uri albe, folosind noul fosfor. Prototipurile au avut o calitate mai bună a culorii decât multe LED-uri comerciale prezente pe piață.
Noul fosfor – realizat din elementele stronțiu, litiu, aluminiu și oxigen (o combinație denumită „SLAO”)

Posted: Feb 19, 2018

Computers aid discovery of new, inexpensive material to make LEDs with high color quality

(Nanowerk News) A team led by engineers at the University of California San Diego has used data mining and computational tools to discover a new phosphor material for white LEDs that is inexpensive and easy to make. Researchers built prototype white LED light bulbs using the new phosphor. The prototypes exhibited better color quality than many commercial LEDs currently on the market.
Researchers published the new phosphor on Feb. 19 in the journal Joule („Mining Unexplored Chemistries for Phosphors for High-Color-Quality White-Light-Emitting Diodes”).
SLAO Phosphor
Under UV light, the SLAO phosphor emits either green-yellow or blue light depending on the chemical activator mixed in. (Image: David Baillot/UC San Diego Jacobs School of Engineering)
Phosphors, which are substances that emit light, are one of the key ingredients to make white LEDs. They are crystalline powders that absorb energy from blue or near-UV light and emit light in the visible spectrum. The combination of the different colored light creates white light.
The phosphors used in many commercial white LEDs have several disadvantages, however. Many are made of rare-earth elements, which are expensive, and some are difficult to manufacture. They also produce LEDs with poor color quality.
Researchers at UC San Diego and Chonnam National University in Korea discovered and developed a new phosphor that avoids these issues. It is made mostly of earth-abundant elements; it can be made using industrial methods; and it produces LEDs that render colors more vividly and accurately.
The new phosphor–made of the elements strontium, lithium, aluminum and oxygen (a combination dubbed „SLAO”)–was discovered using a systematic, high-throughput computational approach developed in the lab of Shyue Ping Ong, a nanoengineering professor at the UC San Diego Jacobs School of Engineering and lead principal investigator of the study. Ong’s team used supercomputers to predict SLAO, which is the first known material made of the elements strontium, lithium, aluminum and oxygen. Calculations also predicted this material would be stable and perform well as an LED phosphor. For example, it was predicted to absorb light in the near-UV and blue region and have high photoluminescence, which is the material’s ability to emit light when excited by a higher energy light source.
LED Phosphor Color Quality Comparison
Untouched shots lit by (left) an LED containing a conventional phosphor and (right) a prototype LED containing the new SLAO phosphor. (Image: Yoon Hwa Kim and Wong Bin Im/Chonnam National University in Korea)
Researchers in the lab of Joanna McKittrick, a materials science professor at the Jacobs School of Engineering, then figured out the recipe needed to make the new phosphor. They also confirmed the phosphor’s predicted light absorption and emission properties in the lab.
A team led by materials science professor Won Bin Im at Chonnam National University in Korea optimized the phosphor recipe for industrial manufacturing and built white LED prototypes with the new phosphor. They evaluated the LEDs using the Color Rendering Index (CRI), a scale that rates from 0 to 100 how accurate colors appear under a light source. Many commercial LEDs have CRI values at around 80. LEDs made with the new phosphor yielded CRI values greater than 90.

The computational quest for a new material
Thanks to the computational approach developed by Ong’s team, discovery of the phosphor took just three months–a short time frame compared to the years of trial-and-error experiments it typically takes to discover a new material.
„Calculations are quick, scalable and cheap. Using computers, we can rapidly screen thousands of materials and predict candidates for new materials that have not yet been discovered,” Ong said.
Ong, who leads the Materials Virtual Lab and is a faculty member in the Sustainable Power and Energy Center at UC San Diego, uses a combination of high-throughput calculations and machine learning to discover next-generation materials for energy applications, including batteries, fuel cells and LEDs. The calculations were performed using the National Science Foundation’s Extreme Science and Engineering Discovery Environment at the San Diego Supercomputer Center.
In this study, Ong’s team first compiled a list of the most frequently occurring elements in known phosphor materials. To the researchers’ surprise, they found that there are no known materials containing a combination of strontium, lithium, aluminum and oxygen, which are four common phosphor elements. Using a data mining algorithm, they created new phosphor candidates containing these elements and performed a series of first-principles calculations to predict which would perform well as a phosphor. Out of 918 candidates, SLAO emerged as the leading material. It was predicted to be stable and exhibit excellent photoluminescence properties.
„It’s not only remarkable that we were able to predict a new phosphor compound, but one that’s stable and can actually be synthesized in the lab,” said Zhenbin Wang, a nanoengineering Ph.D. candidate in Ong’s research group and co-first author of the study.
The phosphor’s main limitation is its less than ideal quantum efficiency–how efficiently it converts incoming light to light of a different color–of about 32 percent. However, researchers note that it retains more than 88 percent of its emission at typical LED operating temperatures. In commercial LEDs, there’s usually a tradeoff with color quality, Ong noted. „But we want the best of both worlds. We have achieved excellent color quality. Now we are working on optimizing the material to improve quantum efficiency,” Ong said.
Source: University of California – San Diego

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

Biocompatibile fibre de nanotehnologie anti-ardere care acționează ca „bandaje vii”(Biocompatible anti-burn nanotechnology fibers that act as ‘living bandages’)

Echipa de cercetători în domeniul nanotehnologiei a reușit să creeze „bandaje” din mai multe straturi fabricate din fibre biodegradabile și nanofilme bioactive multifuncționale, care [bandaje] previne cicatrizarea și accelerează regenerarea țesuturilor.Adăugarea efectului antibacterian prin introducerea de nanoparticule de argint sau prin îmbinarea antibioticelor, precum și creșterea activității biologice la suprafața grupelor hidrofilice (-COOH) și a proteinelor din plasmă sanguină au oferit materialului proprietăți unice de vindecare.
Sa observat o accelerare semnificativă a procesului de vindecare, regenerarea cu succes a țesutului normal acoperit cu piele și prevenirea cicatrizării pe pielea arsă sau deteriorată la aplicarea acestor bandajeri din materialul dezvoltat într-o zonă afectată

Posted: Feb 16, 2018

Biocompatible anti-burn nanotechnology fibers that act as ‘living bandages’

(Nanowerk News) In regenerative medicine, and particularly in burn therapy, the effective regeneration of damaged skin tissue and the prevention of scarring are usually the main goals. Scars form when skin is badly damaged, whether through a cut, burn, or a skin problem such as acne or fungal infection.
Scar tissue mainly consists of irreversible collagen and significantly differs from the tissue it replaces, having reduced functional properties. For example, scars on skin are more sensitive to ultraviolet radiation, are not elastic, and the sweat glands and hair follicles are not restored in the area.
The solution of this medical problem was proposed by the researchers from the NUST MISIS Inorganic Nanomaterials Laboratory, led by PhD Anton Manakhov, a senior researcher. The team of nanotechnology scientists has managed to create multi-layer ‘bandages’ made of biodegradable fibers and multifunctional bioactive nanofilms, which [the bandages] prevent scarring and accelerate tissue regeneration.
Multi-layer bandages made of biodegradable fibers and multifunctional bioactive nanofilms
Multi-layer bandages made of biodegradable fibers and multifunctional bioactive nanofilms. (Image: NUST MSIS)
The addition of the antibacterial effect by the introduction of silver nanoparticles or joining antibiotics, as well as the increase of biological activity to the surface of hydrophilic groups (-COOH) and the blood plasma proteins have provided unique healing properties to the material.
A significant acceleration of the healing process, the successful regeneration of normal skin covering tissue, and the prevention of scarring on the site of burnt or damaged skin have been observed when applying these bandages made of the developed material to an injured area. The antibacterial components of multifunctional nanofibers decrease inflammation, and the blood plasma with an increased platelet level — vital and multi-purposed for every element in the healing process — stimulates the regeneration of tissues. The bandages should not be removed or changed during treatment as it may cause additional pain to the patient. After a certain period of time, the biodegradable fiber simply “dissolves” without any side effects.
“With the help of chemical bonds, we were able to create a stable layer containing blood plasma components (growth factors, fibrinogens, and other important proteins that promote cell growth) on a polycaprolactone base. The base fibers were synthesized by electroforming. Then, with the help of plasma treatment, to increase the material`s hydrophilic properties, a polymer layer containing carboxyl groups was applied to the surface. The resulting layer was enriched with antibacterial and protein components”, noted Elizabeth Permyakova, one of the project members and laboratory scientists.
The research team has already conducted a series of pre-clinical trials jointly with the Research Institute of Experimental and Clinical Medicine (Novosibirsk, Russia). In vitro results have shown that with the application of these innovative bandages the regeneration process has been accelerated twice as quickly. In the near future, the team expects to get results of in vivo drug testing.
Source: NUST MSIS

Experimentele de precizie relevă lacune în teoria lui van der Waals(Precision experiments reveal gaps in van der Waals theory)

Descoperirea grafenului, cu raportul său ridicat de rezistență la greutate, flexibilitate, conductivitate electrică și capacitatea de a forma o barieră impenetrabilă, a condus la o explozie de interes în solidele 2D. TiS 2 este un material arhetipal van der Waals, cu straturi care conțin foi de titan și sulf care interacționează prin legături chimice puternice, unde electronii sunt împărțiți între atomi, rezultând o structură relativ fixă. Între aceste foi, interacțiunile S … S van der Waals atrage straturile unul către altul, permițându-le să se dezvolte, formând materiale solide

Posted: Feb 16, 2018

Precision experiments reveal gaps in van der Waals theory

(Nanowerk News) The discovery of graphene, with its high strength-to-weight ratio, flexibility, electrical conductivity, and ability to form an impenetrable barrier, led to an explosion of interest in 2D solids. Weak, long-range interactions give 2D solids some of their most interesting behaviors; therefore, understanding these interactions is crucial for further developing these materials. However, experimental support for theoretical modelling of the van der Waals interactions that hold these materials’ layers together has been wanting.
Now, an international research group led by the University of Tsukuba and Aarhus University has performed synchrotron X-ray diffraction experiments on titanium disulfide (TiS2)—a transition metal dichalogenide (TMD) material with a layered 2D structure—and compared the results with theoretical calculations. Their benchmark work was recently published in Nature Materials („X-ray electron density investigation of chemical bonding in van der Waals materials”).
Precision experiments reveal gaps in van der Waals theory
“The interaction between layers in van der Waals materials such as TiS2 has a significant bearing on their modification, processing, and assembly,” study co-author Eiji Nishibori says. “By modelling experimental synchrotron data and comparing it with density functional theory calculations, we revealed surprising information about the nature of the electron sharing between layers in these materials.”
TiS2 is an archetypal van der Waals material, with layers comprising sheets of titanium and sulfur interacting through strong chemical bonds, where electrons are shared between atoms, resulting in a relatively fixed structure. Between these sheets, long-range S…S van der Waals interactions attract the layers to one another allowing them to build up, forming solid materials. These interactions are known to be much weaker than those within the 2D sheets, however, using high-energy synchrotron X-ray radiation to precisely measure a single TiS2 crystal, the researchers were able to show that the interlayer interactions are in fact stronger than theory indicates, and involve significant electron sharing.
“This work provides a fundamental understanding of an exciting class of materials with numerous potential applications in technologies such as ion batteries, catalysis, and superconductors,” lead author Hidetaka Kasai says. “Our experiments are the first to reveal the true nature of the interactions that make 2D materials so interesting, and we hope they will underpin many future developments in this area.”
The outstanding agreement of the synchrotron diffraction data with theoretical calculations in describing the intralayer Ti-S interactions, supports the validity of these new-found differences for the long-range interactions across the interlayer gaps. The findings are expected to substantially contribute to the fundamental understanding of weak chemical bonding in 2D layered materials in general, and to the development of TMD materials.
Source: University of Tsukuba

Părul urs polar inspiră textile termice îmbunătățite din nanotehnologie(Polar bear hair inspires nanotechnology enhanced thermal textile)

Textilul țesut cu fibre biomimetice are o izolație termică excelentă, o capacitate activă de electro-încălzire când este dopat cu nanotuburi de carbon (CNT), o bună uzură și o respirabilitate, făcându-l un material promițător pentru izolarea termică și gestionarea termică personală.Textile țesute cu astfel de fibre biomimetice prezintă o excelentă proprietate de izolare termică, precum și o bună aerisire și uzură.
Pe lângă izolarea pasivă a pierderilor de căldură, materialul textil ar putea funcționa și ca încălzitor care poate fi purtat cu materiale electrotehnice, cum ar fi CNT, pentru a determina reacția termică rapidă și electrofilarea uniformă, menținând în același timp caracterul moale și poros pentru o uzură confortabilă.

osted: Feb 16, 2018

Polar bear hair inspires nanotechnology enhanced thermal textile

(Nanowerk News) Inspired by the microstructure and thermal insulation function of the polar bear hair, scientists have used a freeze-spinning technique to continuously fabricate silk fibroin solution into a fiber with aligned porous microstructure.
The textile woven with the biomimetic fibers has an excellent thermal insulation, active electroheating capacity when doped with carbon nanotubes (CNTs), good wearability and breathability, making it a promising material for thermal insulation and personal thermal management.
This work by researchers at Zhejiang University in China has been reported in Advanced Materials („A Thermally Insulating Textile Inspired by Polar Bear Hair”).
Polar bear hair inspires thermal textile
Polar bear hair with hollow core and aligned shell, and continuous and large-scale fabrication of biomimetic porous fiber. a) Photograph of a polar bear. b,c) SEM images showing the hollow core and aligned shell of a polar bear hair, respectively. d) Schematic illustration of the “freezespinning” technique, combining “directional freezing” with “solution spinning” to realize continuous and large-scale fabrication of biomimetic fibers with aligned porous structure, mimicking the polar bear hair. The silk fibroin solution extruded from a pump-controlled syringe is gradually frozen when it passes through a cold copper ring. Collected by a motor, the frozen fiber is further freeze-dried to reserve its porous structure and subsequently woven into a textile. e) Optical image showing a porous fiber collected in a roll. f,g) Optical (f) and SEM (g) images showing a woven textile of biomimetic porous fiber. The fiber diameter is around 200 µm. (© Wiley-VCH Verlag) (click on image to enlarge)
The team uses a freeze-spinning method to realize continuous and large-scale fabrication of fibers with aligned porous structure, mimicking polar bear hairs, which is difficult to achieve by other methods.
Textile woven with such biomimetic fibers shows an excellent thermal insulation property as well as good breathability and wearability.
In addition to passively insulate heat loss, the textile could also function as a wearable heater, when doped with electroheating materials such CNTs, to induce fast thermal response and uniform electroheating while maintaining its soft and porous nature for comfortable wearing.
By Michael is author of two books by the Royal Society of Chemistry: Nano-Society: Pushing the Boundaries of Technology and Nanotechnology: The Future is Tiny.

Membranele de grafină fac Sydney Harbor „băutură”(Graphene membranes make Sydney Harbour ‘drinkable’)

De-a lungul timpului, poluanții chimici și pe bază de ulei acoperă și împiedică filtrele de apă, ceea ce înseamnă că contaminanții trebuie îndepărtați înainte ca filtrele să înceapă. Testele au arătat că Graphair a continuat să funcționeze chiar și atunci când este acoperit cu poluanț”În Graphair am găsit un filtru perfect pentru purificarea apei, care poate înlocui procesele complexe, consumatoare de timp și cu mai multe etape, necesare în prezent, cu un singur pas”.
În timp ce grafenul este cel mai puternic material din lume și poate fi doar un singur atom de carbon subțire, acesta este, de obicei, hidrofug.

Posted: Feb 15, 2018

Graphene membranes make Sydney Harbour ‘drinkable’

(Nanowerk News) Using their own specially designed form of graphene, ‘Graphair’, CSIRO scientists have supercharged water purification, making it simpler, more effective and quicker.
The new filtering technique is so effective, water samples from Sydney Harbour were safe to drink after passing through the filter.
The breakthrough research was published today in Nature Communications („Anti-fouling graphene-based membranes for effective water desalination”).
Graphair sample
A Graphair sample. (Image: CSIRO)
„Almost a third of the world’s population, some 2.1 billion people, don’t have clean and safe drinking water,” the paper’s lead author, CSIRO scientist Dr Dong Han Seo said.
„As a result, millions – mostly children – die from diseases associated with inadequate water supply, sanitation and hygiene every year.
„In Graphair we’ve found a perfect filter for water purification. It can replace the complex, time consuming and multi-stage processes currently needed with a single step.”
While graphene is the world’s strongest material and can be just a single carbon atom thin, it is usually water repellent.
Using their Graphair process, CSIRO researchers were able to create a film with microscopic nano-channels that let water pass through, but stop pollutants.
As an added advantage Graphair is simpler, cheaper, faster and more environmentally friendly than graphene to make.
It consists of renewable soybean oil, more commonly found in vegetable oil.
Looking for a challenge, Dr Seo and his colleagues took water samples from Sydney Harbour and ran it through a commercially available water filter, coated with Graphair.
Researchers from QUT, the University of Sydney, UTS, and Victoria University then tested and analysed its water purification qualities.
The breakthrough potentially solves one of the great problems with current water filtering methods: fouling.
Over time chemical and oil based pollutants coat and impede water filters, meaning contaminants have to be removed before filtering can begin. Tests showed Graphair continued to work even when coated with pollutants.
Without Graphair, the membrane’s filtration rate halved in 72 hours.
When the Graphair was added, the membrane filtered even more contaminants (99 per cent removal) faster.
„This technology can create clean drinking water, regardless of how dirty it is, in a single step,” Dr Seo said.
„All that’s needed is heat, our graphene, a membrane filter and a small water pump. We’re hoping to commence field trials in a developing world community next year.”
CSIRO is looking for industry partners to scale up the technology so it can be used to filter a home or even town’s water supply.
It’s also investigating other applications such as the treatment of seawater and industrial effluents.

Gel utilizează nanoparticule pentru controlul la cerere al picăturilor(

Folosind acest procedeu simplu, două lichide nemiscibile au produs prima structură torturoasă, cu totul lichidă, cu canale submicrometrice interconectate (mai îngust decât părul uman) și cu o formă persistentă. Astfel de „bijeli” (emulsie bicomponentă blocată) pot avea avantaje ca materiale pentru cataliză și stocare a energiei, dar dificultățile în producerea lor și reducerea dimensiunii canalului au limitat valoarea lor până în prezent.
Această abordare nanoparticulo-surfactant este mai simplă și a condus la bijeli cu dimensiuni canale reglabile – chiar până la zece ori mai mici decât este posibil în prezent. Poate fi utilizată o gamă largă de chimicale și concentrații lichide, nanoparticule și polimeri.

Posted: Feb 15, 2018

Gel uses nanoparticles for on-demand control of droplet shapes

(Nanowerk News) Until now, producing liquids that can be shaped and reshaped on demand hasn’t been possible. Scientists discovered a simple way to form stabilized droplets in a variety of structures. Tightly packed nanoparticle-polymer assemblies at droplet surfaces were squeezed into desired shapes assemblies with an electric field. This new approach is a simple route to form droplets of one liquid phase in another liquid. This could lead to the continuous production of discrete, responsive, and reconfigurable all-liquid systems.
This is a unique platform for printing liquids into structures such as small tubes or special sponge-like gels with desired channel dimensions. This printing can structure, re-organize, and indefinitely lock-in the spatial arrangement of liquids. The result? The printed liquids can create optimized pathways for the flow of mechanical, electrical, or optical energy through a material. Tuning compression at the surface may lead to advanced—even revolutionary—energy storage and catalyst technologies.
A water droplet with a trapped nanoparticle-surfactant assembly at its surface
Paralleling your favorite oil-based salad dressing, combining nanoparticles and a soap-like material (surfactant) goes one step further—tunable channels are stabilized in the mixture. Left: A water droplet with a trapped, a.k.a. jammed, nanoparticle-surfactant assembly at its surface. Withdrawing the “water-liking” phase caused the single layer of assemblies to compress. The visible wrinkles developed immediately, suggesting a “solid-like” nature of the squeezed assemblies. And, the process is reversible. Right: A confocal fluorescence image shows the bicontinuous structure of the nanoparticle-surfactant mixtures. (Image: Lawrence Berkeley National Laboratory)
Biological cells compartmentalize the functions of proteins and enzymes within organelles and organize into tissues that coordinate to perform work. Trapping, a.k.a. jamming, nanoparticles at water droplet surfaces offers unparalleled routes to similarly compartmentalize human-made matter resulting in the assembly of structured liquids.
Scientists at Lawrence Berkeley National Laboratory have demonstrated that two liquids that do not mix (called immiscible) can be shaped on demand into stable non-spherical structures. The key is tightly packed nanoparticle surfactants (soap-like materials) at droplet surfaces that are squeezed by an electric field.
A water droplet containing nanoparticles decorated with negatively charged functional groups was first created. The water droplet was in an oil containing polymers with complementary positively charged groups at one end. This allowed the opposite charges to form assemblies at the water-oil interface. An electric field was applied across the droplet, deforming it into an elongated shape with increased surface area.
This allowed more assemblies to form at the droplet surface. Upon removal of the electric field, the droplet attempted to revert to a lower surface area shape (sphere). However, the assemblies were compressed and jammed at the interface. This caused the shape of the liquid to be fixed, “arresting” the liquid in an otherwise highly unstable shape.
Suppressing the instability enables development of a continuous process for forming highly uniform droplets with a wide range of shapes. Moreover, droplet configuration can be controllably changed. Subsequent application of a force such as an electric or magnetic field can cause the droplet to deform. The jammed assemble becomes fluid. This allows its spatial organization to be reconfigured and a new droplet shape to form after removal of the field.
Using this simple process, two immiscible liquids produced the first torturous, all-liquid structure with interconnected sub-micrometer (narrower than a human hair) channels and a persistent shape. Such “bijels” (bicontinuous jammed emulsion) may have advantages as materials for catalysis and energy storage, but difficulties in producing them and reducing the size of their channel have limited their value to date.
This nanoparticle-surfactant approach is simpler and led to bijels with tunable channel sizes—even down to ten times lower than currently possible. A wide range of liquid, nanoparticle, and polymer chemistries and concentrations can be used.
These findings provide valuable guidance for the selection of functionalized nanoparticles and polymers to tune the droplet assembly process to generate structured liquids in a predictable manner.

Publications
A. Toor, B. Helms, and T.P. Russell, “Effect of nanoparticle surfactants on the breakup of free-falling water jets during continuous processing of reconfigurable structured liquid droplets.External link” Nano Letters 17, 3119 (2017). [DOI: 10.1021/acs.nanolett.7b00556]
C. Huang, J. Forth, W. Wang, K. Hong, G. Smith, B.A. Helms, and T.P. Russell, “Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactantsExternal link.” Nature Nanotechnology 12, 1060 (2017). [DOI: 10.1038/nnano.2017.182]