FOM-researcher Wim de Jeu and his fellow researchers from the United States of America and from Chile will announce this in Science, on August 3rd, 2007. The wrinkles arise, being influenced by the surface tension of the drop of water. Consequently, such a floating polymer sheet is a fine model for studying the behaviour of thin films in fluids. This combination is generally found in biological and synthetic soft materials.
The researchers used thin sheets (in academic jargon ‘films’) of polystyrene for their measurements, which they attached to a glass substratum. The thickness of the thin sheets, defined by means of x-ray reflectivity, varied from 31 to 233 nanometers. Then, they cut a circle 22.8 millimetres in diameter in each of the sheets and after that they dipped it into a Petri dish in distilled de-ionized water. In the Petri dish the surrounded part of the thin sheets came off and was floating on the water. As polystyrene is so-called ‘hydrophobic’, the surface tension flattens the polystyrene at the edge of the sheet. Thus, floating flat discs of polystyrene came into being. If the researchers then placed a droplet of water in the centre or pressed a needle, as a consequence of this disruption regular patterns of wrinkles arose that were facing outwards.
The wrinkled pattern appears to correspond nicely to the prognosis of a recently developed theory. This theory converts the surface tension of the drop of water in capillary forces that are affecting the polymer film. The researchers now combined the scaling relations that were developed for the length of the wrinkles with those for the number of wrinkles that will arise. This will produce a measuring standard to define the elasticity and thickness of very thin polymer sheets. In order to accomplish this, it appears that in actual practice, all that is necessary is a Petri scale with water, a plain microscope and a digital camera, because the patterns are extremely well visible at a small magnification. Next, they tested their method on polymer films that they had provided with plasticiser in order to vary the elasticity of the films. Even then the method produces reliable results to the thickness of the films.
The method that the researchers have been developing, just provides another large advantage. When they disrupt the film by placing a drop of water or pressing a needle, wrinkles will arise. In time the wrinkles will disappear, because the disruptions are spreading out all over the film. The film is ‘relaxing’ so to speak. Other research methods are applying the films to a firm substratum, which may lead to mechanical tensions in the sheets. These are disrupting the ‘relaxation’ of the film, which influences the measuring results. When the films are floating in or on a fluid, similar tensions may then ebb to the underlying fluid, after which the measurements will solely reproduce the process of the wrinkling.
Huub Eggen | alfa
Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University
Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
21.08.2017 | Materials Sciences
21.08.2017 | Health and Medicine
21.08.2017 | Materials Sciences