Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Defining the thickness of polymer films by a drop of water

03.08.2007
Place a drop of water on a floating thin polymer sheet and wrinkles will arise around the drop. You may see this even with a plain microscope. The amount of wrinkles and their lengths appear to be a straight measure for the elasticity and the thickness of the polymer sheet.

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
Further information:
http://www.fom.nl/live/english/news/artikel.pag?objectnumber=64898

More articles from Physics and Astronomy:

nachricht From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison

nachricht Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

New pop-up strategy inspired by cuts, not folds

27.02.2017 | Materials Sciences

Sandia uses confined nanoparticles to improve hydrogen storage materials performance

27.02.2017 | Interdisciplinary Research

Decoding the genome's cryptic language

27.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>