Researchers in Hong Kong have developed a novel method for moving a water drop along a controlled path on a superhydrophobic surface. The method requires a superhydrophilic steel ball which, due to it's high wetting properties, is attracted to water and will become embedded in a water drop. The water, by contrast, is repelled by the superhydrophobic surface on which it sits. A magnet under the surface is used to control - with an amazing degree of precision - the location and movement of the drop (and can even pickup additional water drops in its path.
Fuente: Ramé-Hart Newsletter, Julio.
En el siglo XXI: Conocimiento e Innovación, más vigentes que nunca.
Nuevos Productos: Carreteras piezoeléctricas: un proyecto que pudo realizarse en Chile casi 20 años atrásEscrito por agsens el 17-04-22
Almost 20 years ago in Chile, a young PhD in Materials Science, postulated the same application and tried its implementation. His project had no support and he migrated of the country. Now this is a reality in California.
Nuevos Productos: Nuevo dispositivo termofotovoltaico para cosecha de energía desde calor de desechoEscrito por agsens el 17-04-13
New device thermophotovoltaics for energy harvesting from waste heat
A new reconfigurable device that emits patterns of thermal infrared light in a fully controllable manner could one day make it possible to collect waste heat at infrared wavelengths and turn it into usable energy.
The new technology could be used to improve thermophotovoltaics, a type of solar cell that uses infrared light, or heat, rather than the visible light absorbed by traditional solar cells. Scientists have been working to create thermophotovoltaics that are practical enough to harvest the heat energy found in hot areas, such as around furnaces and kilns used by the glass industry. They could also be used to turn heat coming from vehicle engines into energy to charge a car battery, for example.
A new metamaterial film provides cooling without needing a power input. Made out of glass microspheres, polymer and silver, the material uses passive radiative cooling to dissipate heat from the object it covers. It emits the energy as infrared radiation and also reflects solar light The randomized glass-polymer film is the one doing the magic. The polymer-microsphere film is transparent to the whole solar spectrum but radiates infrared. The broad collective resonance among the microspheres ensures the film is highly emissive of infrared within the atmospheric range of 8–13 μm. This property therefore enhances the naturally occurring radiative cooling. Meanwhile, sunlight travels through the metamaterial and is reflected back by the silver coating, which prevents any solar heating.
Fuente: Physics World
GEOMIMETICS: A NEW RESEARCH FIELD?
If well the biomimetics has been widely diffused by the scientific community, had to wait many more years for what the concept of "geomimetics" to emerge and to start to be accepted as a new research field.
In times of student in materials science starting this new millenium, Juan Aguilera, Technology Director at AGSENS, had the chance to carry out a research in hydrothermal thin solid films and since then, thinking that the process to obtain films could conceptualize as a geomimetic strategy. More than 10 year after, today, reviewing in internet, appear a few publications and incipient denominations in some books about ceramics, while in US Patent Data base appear 0 patents and Wikipedia indicates "The page Geomimetics does not exist. You can ask for it to be created". Neither there is a book about the topic or a scientific journal. Given the above, we can say that this science is in embryonic state, even though, it's known by some archeologists that many ancient buildings in rock, are based on geopolymers, i.e. synthesized rocks by geomimetic processing carried out by ancient civilizations. The relation between geomimetics and geopolymers is something which is just beginning to interrelate. The implicancies scientific, technical and industrial are manifest for this new research field.Continuar Leyendo
Mechanochromic devices have remarkable capabilities to change transparency and/or colour in response to mechanical stimuli, making them attractive for a wide range of applications in smart windows, strain sensors, encryption, tunable wetting systems, between others. In fact, some marine life forms have evolved camouflage traits involving dynamic and reversible alteration of their transparency, fluorescence, and colouration via muscle-controlled surface structures and morphologies. A number of marine organisms use muscle-controlled surface structures to achieve rapid changes in colour and transparency with outstanding reversibility. Inspired by these display tactics, scientists have develop analogous deformation-controlled surface-engineering approaches via strain-dependent cracks and folds to realize the following four mechanochromic devices: (1) transparency change mechanochromism (TCM), (2) luminescent mechanochromism (LM), (3) colour alteration mechanochromism (CAM) and (4) encryption mechanochromism (EM). These devices are based on a simple bilayer system that exhibits a broad range of mechanochromic behaviours with high sensitivity and reversibility. The TCM device can reversibly switch between transparent and opaque states. The LM can emit intensive fluorescence as stretched with very high strain sensitivity. The CAM can turn fluorescence from green to yellow to orange as stretched within 20% strain. The EM device can reversibly reveal and conceal any desirable patterns.
Why the Cheerios floating on the top of the milk have a tendency to clump together?
This behavior is caused by the surface tension of milk. The molecules at the liquid surface exhibit stronger cohesive bonding than the molecules below the surface. As a result, the surface behaves like a thin film. Since the Cheerios are floating, an upward meniscus forms at the liquid/Cheerio interface. Since the Cheerios are buoyant, they want to move to the highest point - the center of the bowl, to the edge, and to each other.
A contact angle forms where the milk touches the liquid as a result of strong surface energy and poor wetting. The resulting meniscus is upward due to the buoyancy of the Cheerio while the meniscus on of paper clip curves downward due to gravity and its greater density.
The Cheerios effect is useful to understand how self-assembly can work with nanoscopically small parts of uniform shape.
On a related note, while we were studying Cheerios, we became curious about the surface tension of milk. So we took some measurements using a ramé-hart Model 250 with DROPimage Advanced. We found that grade A 2% homogenized and pasteurized cows milk from the grocery store has a surface tension of 48 mN/m. Fatty acids and proteins are the surface-active agents which lower the surface tension to a value lower than that of water. We also found that the surface tension of milk is inversely proportional to the fat content. Thus, we discovered that a tensiometer can replace a lactometer for measuring the creaminess of milk.
Desde Newsletter Ramé-Hart Agosto, 2016Continuar Leyendo
Materials that combine the properties of fluidity and permanent porosity could therefore offer technological advantages. Free-flowing liquids whose bulk properties are determined by their permanent porosity. To achieve this, was designed cage molecules that provide a well-defined pore space and that are highly soluble in solvents whose molecules are too large to enter the pores. The concentration of unoccupied cages can thus be around 500 times greater than in other molecular solutions that contain cavities, resulting in a marked change in bulk properties, such as an eightfold increase in the solubility of methane gas. This is a new class of functional porous materials for chemical processes. Unifying design principle for these materials is the avoidance of functional groups that can penetrate into the molecular cage cavities. doi:10.1038/nature16072
Physicists Miroshnickenko and colleagues have found a new way to confine electromagnetic energy without it leaking using nonradiating anapole modes [Nature Communications, 2015]. Nonradiating electromagnetic sources continue to be of interest as a model for stable atoms to understand why orbiting electrons do not radiate, and have potential applications for combatting energy losses and explaining dark matter. The radiationless anapole mode is achieved by dividing the current between two different components; a conventional electrical dipole and a toroidal dipole. Using a Nanonics CryoView MP and transmission NSOM mode with Nanonics NSOM probes, these scientists tested this theory using near-field characterization of single silicon nanodisks. They observed the disc's cancelling of visible light, thus rendering the feature effectively invisible at that wavelength.
(c) 2015 AGSENS Equipamiento Tecnocientífico