fuckyeahfluiddynamics:

fuckyeahfluiddynamics:

Defrosting and deicing surfaces is an energy-intensive affair, with lots of heat lost to warming up system components rather than the ice itself. In a new study, researchers explore a faster and more efficient method that focuses on heating just the interface. They coated their working surface in a thin layer of iridium tin oxide, a conductive film used in defrosting. Then, once the surface was iced over, they applied a 100 ms pulse of heating to the film. That localized heat melted the interface, and gravity pulled away the detached ice. Compared to conventional defrosting methods, this technique requires only 1% of the energy and 0.01% of the time. If the method scales reliably to applications like airplane deicing, it would provide enormous savings in time and energy. (Image and research credit: S. Chavan et al.)

Chemists obtain new material for antibacteri…

Chemists obtain new material for antibacterial food coatings

RUDN University chemists have developed a simple and convenient method for producing derivatives of the natural polymer chitosan. These derivatives are non-toxic and have a pronounced antibacterial activity at the level of modern antibiotics. These substances can be used in the production of antibacterial protective films for food. The article is published in the journal Food Chemistry.

Preservatives are widely used in the food industry. They are necessary to extend the shelf life of products. On the other hand, preservatives reduce food quality. Some of them can cause allergies (benzoic acid) or be toxic (nitrates, nitrites). Synthetic waxy substances used to coat fruits can be carcinogenic (biphenyl is prohibited in the US and EU). This explains the importance of finding new preservatives that are effective and safe.

Chitosan is a natural polymer derived from chitin, the main component of insect and crustacean shells. It has antibacterial properties and is already used in the food industry for packaging and coating products with a protective film. However, its activity is far inferior to antibiotics.

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A new, natural wax coating makes garments wa…

A new, natural wax coating makes garments water-resistant and breathable

There is a growing concern over the environmental impact of textile production and many waterproof products on the market are prepared with toxic chemicals. This is increasing demand for new sustainable material alternatives, but making non-toxic, breathable and waterproof textiles, sustainably and economically has thus far proven to be a challenge.

Now, Aalto researchers have developed an ecological and water repellent wax particle coating suitable for wood cellulose fibres, which also retains the breathability and natural feel of the textile. The coating uses carnauba wax, which is also used in such things as medicines, foodstuffs, as well as the surface treatment of fruits and car waxes. The new coating is suitable not only for textiles but also for other cellulose-based materials.

During the processing, the wax is thawed and decomposed in water into wax particles that are anionic (i.e. negatively charged) just like cellulose. For the wax particles to adhere well to the cellulose surface, something cationic (i.e. positively charged) is needed as a buffer, since the oppositely charged particles attract one another. In previous studies, a natural protein called polylysine was used for this.

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Secure Printing Using Pure Water As Invisibl…

Secure Printing Using Pure Water As Invisible Ink [Video]

Researchers in China have developed a rewriteable paper coating that can encrypt secret information with relatively low-tech invisible ink—water. A message printed out by a water-jet printer on a manganese-complex-coated paper is invisible to the naked eye, but the message reveals itself under 254 nm UV light. The paper can be ready for another round of printing after erasing the message by heating it with a blow dryer for 15-30 seconds. The method, presented September 25, 2019, in the journal Matter, allows reversible secure printing for at least 30 cycles.

“We used to regulate organic materials’ photoluminescence properties through modifying the molecular structure,” says senior author Qiang Zhao, of the Institute of Advanced Materials, Nanjing University of Posts and Telecommunications. “But recently we discovered that it only needs an external stimulus to change its optical or electrical properties. We developed a rewritable security printing method by utilizing the photoluminescence responses of manganese complex to water.

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Glasses: Smart glass

Glasses: Smart glass

Smart materials are those materials specifically designed to have one or more properties that will change in a desired manner in response to an anticipated external stimuli. Smart glass, then, is any type of glass that fits this category, of which there are many.

Thermochromic glasses are glasses which change color (typically tint) in response to changes in heat. Often these glasses are responsive enough to change in direct response to sunlight, letting in more light (i.e. being more transparent) when the sun is not shining as brightly. This can help control the amount of light needed within a structure, as well as the energy consumption of heating or cooling, depending on the climate. Thermochromic windows are typically produced in layers, as shown in the upper left image above.

Electrochromic glasses, then, are glasses which change color (or tint) in response to the amount of voltage applied to the glass. These types of glasses (often used for windows) allow occupants to tint the glass at will, sometimes for the same reasons as mentioned above, but occasionally simply for comfort or privacy. Electrochromic glasses offer more control than thermochromic glasses, but it requires the ability to control the voltage as well. (The amount of electricity used, however, can be far less than the amount that could potentially be saved by allowing for natural lighting.)

Finally, photochromic glasses also have a similar effect, those these glasses react to the presence of light, not heat as with thermochromic glasses. Photochromic glasses are most popular in lenses.

Other types of smart glass include suspended particle and polymer dispersed liquid crystals. The latter is not actually a form of glass, but rather a layer between the glass. As with electrochromic glass, the application of voltage changes the tint, but PDLCs react much faster than electrochromic materials.

Technically speaking, it is often glazings added to glasses that help produce these effects, which is why windows of these types of glasses are constructed in layers. The movement of ions or electrons through the layers can often be the basis for the change in tint. As such, materials which claim to be ‘smart glass’ are typically combinations of glass and coatings, thin films, or other layers between the glass. There are, however, exceptions.

Sources/Further Reading: ( 1 – image 1 ) ( 2 – image 2 ) ( 3 – image 3 ) ( 4 – image 4 ) ( 5 – image 5 ) ( 6 ) ( 7 ) ( 8 ) ( 9 ) ( 10 )

NRL pigment package for ships slows discolor…

NRL pigment package for ships slows discoloration, lowers solar temperature load

A pigment package designed by the U.S. Naval Research Laboratory to slow discoloration of the exterior coating on surface ships has started to make its way into the fleet and is producing early, positive results.

NRL researchers created the pigmentcombination to satisfy the fleet requirement for the Navy standard “haze gray” paint that will remain color stable for longer than current coatings. While many paint manufacturers had produced new coatingtechnologies that solved a variety of other problems, such as corrosion and delamination, some ships still showed discoloration in as little as 18 months. Additionally, different coatings from different manufacturer’s fade to different hues, resulting in an inconsistent appearance between the original coatings and any in-service touch-ups or repairs.

“We had a good idea on how to solve the issue, and we leveled the playing field by providing the pigment combination to all companies at the same time,” said Dr. Erick Iezzi, senior research chemist in the Center for Corrosion Science and Engineering at NRL.

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One-molecule-thick coating to help improve d…

One-molecule-thick coating to help improve disease and drug testing

A new breakthrough has the potential to improve sensors used to test for diseases and detect doping in sports.

An international research team led by scientists from Lancaster University have created a coating only one molecule thick that modifies the surface of sensor electrodes.

The molecule used, called beta-cyclodextrin, has a funnel shape with a hydrophobic inside and a hydrophilic outside. The combination of these two properties works together to ensure that only molecules of the correct size and type will fit inside—thus ensuring the sensor only detects substances it is tuned for.

The process, which involves electrochemically grafting the beta-cyclodextrin onto the surface of graphite electrodes, is also easy to apply—it can be added in one simple step within minutes, without any special equipment or harmful chemicals—something the researchers believe makes the process cheap and scalable.

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Nanocoating prevents greasy smears

Nanocoating prevents greasy smears

Not only are greasy fingerprints on shiny stainless steel surfaces unattractive, they also attack the surface. A new nanocoating being developed by Fraunhofer researchers will in the future prevent the annoying smudges that result from fingers touching stainless steel surfaces. The key to their approach: special nanoparticles added to the coating.

The shiny new refrigerator features an attractive stainless steel front. But it doesn’t take long before the door is covered in dark fingerprints that are difficult to remove with only a cloth and detergent; the job actually calls for some arduous polishing. Fingerprints like these are more than just unsightly, the grease film also attacks the metal surface.

Say goodbye to greasy smears

Together with their colleagues at FEW Chemicals GmbH in Wolfen, researchers from the Fraunhofer Institute for Microstructure of Materials and Systems IMWS in Halle are now working to put an end to smears like these. The secret lies in a coating layer containing special additives and which is water and oil repellent. This layer’s effects are twofold: When the particles integrated in the coating settle on the surface of the stainless steel, the surface becomes rougher and its surface area increases. When a finger comes into contact with the refrigerator door, it only touches the raised points on the surface and the grease on the fingertip never reaches the “valleys” of the stainless steel surface. This means the surface area which actually comes into contact with the grease is kept very small. In addition the refractive index of the coating has been adjusted so that it matches that of the skin’s natural oil content. This means light is reflected by the coated stainless steel surface in about the same manner as by a surface that has been touched by sticky fingers. As a result, the fingerprints are hardly noticeable.

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Polymer-coated gold nanospheres do not impai…

Polymer-coated gold nanospheres do not impair the innate immune function of human B lymphocytes

Over the past 20 years, the use of nanoparticles in medicine has steadily increased. However, their safety and effect on the human immune system remains an important concern. By testing a variety of gold nanoparticles, researchers at the University of Geneva (UNIGE) and collaborators are providing first evidence of their impact upon human B lymphocytes—the immune cells responsible for antibody production. The use of these nanoparticles is expected to improve the efficacy of pharmaceutical products while limiting potential adverse effects.

These results, published in the journal ACS Nano, could lead to the development of more targeted and better tolerated therapies, particularly in the field of oncology. The methodology also makes it possible to test the biocompatibility of any nanoparticle at an early stage in the development of a new nanodrug.

Responsible for the production of antibodies, B lymphocytes are a crucial part of the human immune system, and therefore an interesting target for the development of preventive and therapeutic vaccines. However, to achieve their goal, vaccines must reach B lymphocytes quickly without being destroyed, making the use of nanoparticles particularly interesting.

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Ultraviolet light-based coating shows promis…

Ultraviolet light-based coating shows promise in self-disinfecting surfaces in medical facilities, public areas

The World Health Organization warns that antibiotic resistance is one of the biggest global threats and predicts that worldwide death rates from this threat could skyrocket past 10 million a year by 2050, becoming more deadly than cancer, which kills 8.2 million people worldwide each year.

Purdue University researchers are developing a method of combating that antibiotic resistance through self-disinfecting surfaces that would kill bacteria, even those known as superbugs. The researchers are developing an ultra-thin coating, smaller than a micrometer, made of ultraviolet lightemitting diodes (UV-LED) that could be integrated into materials, such as vinyl flooring, wall coverings, door handles and even toilet seats.

“This ultra-thin coating kills any germs, bacteria, viruses, fungi and parasites. They cannot become resistant because any DNA that could make them resistant gets destroyed during the disinfection,” said Tillmann Kubis, a research assistant professor in Purdue’s School of Electrical and Computer Engineering, who is leading the research.

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