Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Switchable Adhesive

24.07.2007
Gel- and polymer-coated surfaces stick together and separate in response to an environmental stimulus

Two surfaces stick together, separate, and stick together again—on command. This discovery by a team of researchers from the Universities of Sheffield (UK) and Bayreuth contradicts our day-to-day experience. In the animal kingdom, geckos can climb up vertical inclines, displaying an incredible switchable adhesion as they do so. Insects also use another form of switchable adhesion to sit on your ceiling and then fly off before you climb up on your chair with a rolled-up newspaper. How these animals can switch off and on adhesion is not yet understood in detail. But the scientists led by Mark Geoghegan reveal the secret of their “intelligent” adhesion in the journal Angewandte Chemie.

One of the surfaces involved consists of a polyacid gel, a three-dimensionally cross-linked polymer containing many acid groups. This polymer network is so heavily soaked in liquid that it forms a solid, gelatinous mass. The second surface is a silicon chip onto which a polybase has been deposited. This polybase consists of polymer chains that stretch brush-like from the support and contain many basic groups. In water or slightly acidic solution, the acidic groups carry a positive charge while the basic groups are negatively charged; this causes them to attract each other. In addition to this electrostatic attraction, hydrogen bonds are also formed, which causes the two surfaces to be tightly stuck together.

If the surrounding solution is made more strongly acidic (a pH value of about 1), the bonds break up, the basic groups lose their charge, and the electrostatic attraction lets up. The two surfaces can then be slowly and carefully separated from each other without any damage. This detachment is reversible: If the pH value is raised again, making the solution less acidic, the gel and “brush” stick to each other once again. This cycle can be repeated many times by simply changing the pH value.

... more about:
»Stick »acidic »adhesion

Possible applications for such “smart” surface pairs include microelectromagnetic components (actuators), components for microfluidic systems, or carriers for pharmacological agents that could release their cargo under specific physiological conditions.

Author: Mark Geoghegan, University of Sheffield (UK), http://homepage.mac.com/mag16/

Title: Controlling Network–Brush Interactions to Achieve Switchable Adhesion

Angewandte Chemie International Edition, doi: 10.1002/anie.200701796

Mark Geoghegan | Angewandte Chemie
Further information:
http://homepage.mac.com/mag16/
http://pressroom.angewandte.org

Further reports about: Stick acidic adhesion

More articles from Life Sciences:

nachricht Water world
20.11.2017 | Washington University in St. Louis

nachricht Carefully crafted light pulses control neuron activity
20.11.2017 | University of Illinois at Urbana-Champaign

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Antarctic landscape insights keep ice loss forecasts on the radar

20.11.2017 | Earth Sciences

Filling the gap: High-latitude volcanic eruptions also have global impact

20.11.2017 | Earth Sciences

Water world

20.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>