Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study Explores Physics of Wrinkling, Folding

19.05.2008
Scientists at the University of Chicago and the University of Santiago in Chile have explained, for the first time, the physics that governs how thin materials at scales millions of times different in thickness make the transition from wrinkles into folds under compression.

Scientists at the University of Chicago and the University of Santiago in Chile have explained, for the first time, the physics that governs how thin materials at scales millions of times different in thickness make the transition from wrinkles into folds under compression.

The study stems from a research program at the University of Chicago aimed at understanding the characteristics of lung surfactant, a microscopically thin membrane that facilitates breathing. But the findings would apply both to the design of foldable electronics and to the production of synthetic lung surfactant for therapeutic uses.

“Our paper is getting at the generality of these types of transitions,” said Luka Pocivavsek, an M.D./Ph.D. student at the University of Chicago. Lung surfactant has the ability to wrinkle and fold under pressure, then gracefully pop back into a stiff configuration when relaxed. “It’s not necessarily something special about lung surfactant that lets it do this. It’s really the fact that lung surfactant behaves like an elastic, thin sheet,” Pocivavsek said.

He and his co-authors will publish their results in the May 16 issue of the journal Science. His co-authors include Ka Yee Lee, Associate Professor in Chemistry, and Binhua Lin, Senior Research Associate in the Center for Advanced Radiation Sources (CARS), both at the University of Chicago; and Enrique Cerda, Associate Professor of Physics at the University of Santiago. Also contributing to the study were two summer researchers: Sebastián Johnson, an undergraduate exchange student from the University of Santiago; Andrew Kern, a 2007 graduate of the University of Chicago Laboratory Schools, now at Northwestern University; and Robert Dellsey of Tulane University.

Lee’s laboratory typically works with materials that resemble lung surfactant, which measures only 2 nanometers in thickness (the width of several atoms). “When we breathe, lung surfactant is compressed in the air sacs during exhalation,” Pocivavsek said. “It’s compressed so far that eventually it has to transition from being just a flat surface to something that’s now crumpled.”

The chief component of lung surfactant is called dipalmitoylphosphatidylcholine (DPPC). Pocivavsek likened DPPC in its purest form to a porcelain plate. “If you push on it hard enough, it’s going to crack,” he said. If lung surfactant consisted of 100 percent DPPC, the cracked pieces would hold together under the pressure during exhalation. But the plate would fall apart upon inhalation, which would decrease the stress.

Scientists can alter the properties of their experimental surfactants by mixing another type of lipid (fat) with the DPPC. The “magic lung-surfactant-lipid composition” is approximately 70 percent of the electrically neutral DPPC and 30 percent of a charged lipid, Lee said.

“It’s a tricky thing,” she said, balancing the stiffness of DPPC with the fluid behavior of the other lipid component. “In natural lung surfactant, various lung surfactant proteins are involved as well.”

Lee and Pocivavsek have attempted to clarify what causes the wrinkle-to-fold transition in experimental lung surfactant under stress, but with inconclusive results. “It’s just a difficult experiment because the lipid film is so thin and other competing effects prevent us from unequivocally observing the transition,” Lee said.

But thanks to the Chicago-Chile Inter-American Materials Collaboration, funded by the National Science Foundation, Pocivavsek began a new line of related experiments on wrinkling and folding in a much thicker polyester film to get insights into the wrinkling-to-folding transition. At 10 microns thickness—narrower than a hair—the polyester film is thick enough to see with the naked eye.

Pocivavsek spent three months at the University of Santiago in 2006 with the theoretical collaborator of the project, Enrique Cerda, returning for another month last December. In Santiago, Luka started exploring the response of polyester films when put under stress. “They do some really amazing science,” Pocivavsek said of Cerda and his associates.

Pocivavsek continued the experiment in Lee’s laboratory upon his return from Santiago. Along with summer students Sebastián Johnson and Andrew Kern, he was able to precisely measure the wrinkles and folds in the polyester film. Binhua Lin at CARS, meanwhile, used light microscopy and X-ray techniques to measure wrinkling and folding in three layers of gold nanoparticles measuring only 15 nanometers in thickness. Working with Pocivavsek and Dellsy, her experiments provided data on a third type of material at yet another length scale. The collaboration was further enhanced by Cerda’s visit to Chicago last summer.

These findings enabled the group to verify Cerda’s theoretical calculations about how lung surfactant behaves, and document the universal dynamics of wrinkling and folding over a vast range of length scales in different materials.

When first compressed, an elastic material begins to wrinkle. The stress then focuses at a certain point, causing a trough or a peak to grow. Lung surfactant has the ability to reverse this stress focusing, allowing the folding that occurs on exhalation to smoothly stretch back into its previous state with inhalation.

A crumpled piece of paper shows ridges when flattened out again because there is nowhere for the focused energy to escape. Not so with a membrane stretched over a reservoir, where fluid will absorb the energy, preventing ridge formation. The principle has technological as well as biomedical implications.

“What if we want to have electronic paper?” Lee asked. “Make a polymer composite that would never wrinkle.”

And in the biomedical arena, researchers may be able to develop a therapy for sufferers of Respiratory Distress Syndrome that mimics the physical properties, rather than the chemical composition of natural lung surfactant. “We might not necessarily have to use the particular lung surfactant components that nature uses,” Pocivavsek said.

In addition to the NSF, support for Lee and Pocivavsek’s research comes from the U.S.-Israel Binational Foundation, the University of Chicago’s Medical Scientist Training Program, the Dreyfus Foundation, the March of Dimes and the U.S. Department of Energy.

Steve Koppes | newswise
Further information:
http://www.uchicago.edu

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>