By applying specific voltages, the team has also shown that it can achieve this control over large and curved surface areas.
This image shows various stages of polymer changes. Credit: Xuanhe Zhao
"By changing the voltage applied to the polymer, we can alter the surface from bumpy to smooth and back again," said Xuanhe Zhao, assistant professor of mechanical engineering and materials science at Duke's Pratt School of Engineering. "There are many instances, for example, when you'd want to be able to change at will a surface from one that is rough to slippery and back again."
Scientists have long been able to create different patterns or textures on plastics through a process known as electrostatic lithography, in which patterns are "etched" onto a surface from an electrode located above the polymer. However, once the patterns have been created by this method, they are set permanently.
"We invented a method which is capable of dynamically generating a rich variety of patterns with various shapes and sizes on large areas of soft plastics or polymers," Zhao said. The results were published online in the journal Advanced Materials.
"This new approach can dynamically switch polymer surfaces among various patterns ranging from dots, segments, lines to circles," said Qiming Wang, a student in Zhao's laboratory and the first author of the paper. "The switching is also very fast, within milliseconds, and the pattern sizes can be tuned from millimeter to sub-micrometer."
The findings follow Zhao's earlier studies, which for the first time captured on videotape how polymers react to changing voltages. Those experiments showed that as the voltage increases, polymers tend to start creasing, finally leading to large craters. This explained in physical terms, for example, why polymers used to insulate electric wires tend to fail over time. The new lithography strategy takes useful insights from this failure mechanism.
On a more fanciful note, Zhao described the possibility of creating rubber gloves whose fingerprints could be changed on demand.
"The changeable patterns we have created in the laboratory include circles and straight and curved lines, which are basic elements of fingerprints," Zhao said. "These elements can be dynamically patterned and changed on a glove surface that covers fingertips.
"A spy's glove may be cool, but probably not for everyone," Zhao said. "However, the same technology can produce gloves with on-demand textures and smoothness tuned for various applications, such as climbing and gripping. Furthermore, surfaces capable of dynamically changing patterns are also useful for many technologies, such as microfluidics and camouflage."
Other potential usages of the new method include creating surfaces that are self-cleaning and water-repellant, or even as platforms for controlled-release drug-eluting devices.
The study was supported by the Research Triangle Materials Research Science and Engineering Center, which is funded by the National Science Foundation, as well as the Lord Foundation and a Haythornthwaite Research Initiation grant.
Other members of the research team were Duke's Mukarram Tahir and Jianfeng Zang.
Richard Merritt | EurekAlert!
For graphite pellets, just add elbow grease
23.03.2018 | Rice University
23.03.2018 | Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy