Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanocomposities yield strong, stretchy fibers

22.01.2007
Lycra-like materials were inspired by spider silk

Creating artificial substances that are both stretchy and strong has long been an elusive engineering goal. Inspired by spider silk, a naturally occurring strong and stretchy substance, MIT researchers have now devised a way to produce a material that begins to mimic this combination of desirable properties.

Such materials, known as polymeric nanocomposites, could be used to strengthen and toughen packaging materials and develop tear-resistant fabrics or biomedical devices. Professor Gareth McKinley, graduate student Shawna Liff and postdoctoral researcher Nitin Kumar worked at MIT's Institute for Soldier Nanotechnologies (ISN) to develop a new method for effectively preparing these materials. The research appears in the January issue of Nature Materials.

Engineers are already able to create materials that are either very strong or very stretchy, but it has been difficult to achieve both qualities in the same material. In the last few years scientists have determined that the secret behind the combined strength and flexibility of spider silk lies in the arrangement of the nano-crystalline reinforcement of the silk while it is being produced.

"If you look closely at the structure of spider silk, it is filled with a lot of very small crystals," says McKinley, a professor of mechanical engineering. "It's highly reinforced."

The silk's strength and flexibility come from this nanoscale crystalline reinforcement and from the way these tiny crystals are oriented towards and strongly adhere to the stretchy protein that forms their surrounding polymeric matrix.

Liff, a Ph.D. student in mechanical engineering, and Kumar, a former MIT postdoctoral associate, teamed up to figure out how to begin to emulate this nano-reinforced structure in a synthetic polymer (A polymer or plastic consists of long chains composed of small repeating molecular units). Numerous earlier unsuccessful attempts, tackling the same issue, relied on heating and mixing molten plastics with reinforcing agents, but Liff and Kumar took a different approach: They focused on reinforcing solutions of a commercial polyurethane elastomer (a rubbery substance) with nanosized clay platelets.

They started with tiny clay discs, the smallest they could find (about 1 nanometer, or a billionth of a meter thick and 25 nanometers in diameter). The discs are naturally arranged in stacks like poker chips, but "when you put them in the right solvent, these 'nanosized poker chips' all come apart," said McKinley.

The researchers developed a process to embed these clay chips in the rubbery polymer-first dissolving them in water, then slowly exchanging water for a solvent that also dissolves polyurethane. They then dissolved the polymer in the new mixture, and finally removed the solvent. The end result is a "nanocomposite" of stiff clay particles dispersed throughout a stretchy matrix that is now stronger and tougher.

Importantly, the clay platelets are distributed randomly in the material, forming a structure much like the jumble that results when you try to stuff matches back into a matchbox after they have all spilled out.

Instead of a neatly packed arrangement, the process results in a very disorderly "jammed" structure, according to McKinley. Consequently the nanocomposite material is reinforced in every direction and the material exhibits very little distortion even when heated to temperatures above 150 degrees Celsius.

In a Nature Materials commentary that accompanied the research paper, Evangelos Manias, professor of materials science and engineering at the University of Pennsylvania, suggests that "molecular composites" such as those developed by the MIT group are especially suitable for new lightweight membranes and gas barriers, because the hard clay structure provides extra mechanical support and prevents degradation of the material even at high temperatures. One possible use for such barriers is in fuel cells.

The U.S. military is interested in such materials for use in possible applications such as tear-resistant films or other body-armor components. The military is also interested in thinner, stronger packaging films for soldiers' MREs (meals ready to eat) to replace the thick and bulky packaging now used.

Fabric companies have also expressed interest in the new materials, which can be used to make fibers similar to stretchy compounds such as nylon or Lycra. The new approach to making nanocomposites can also be applied to biocompatible polymers and could be used to make stents and other biomedical devices, McKinley said.

The research was funded by the U.S. Army through MIT's Institute for Soldier Nanotechnologies and by the National Science Foundation. McKinley's team was assisted by technical staff at the ISN, including research engineer Steven Kooi, who helped prepare special samples for transmission electron microscopy.

Elizabeth A. Thomson | MIT News Office
Further information:
http://www.mit.edu

More articles from Materials Sciences:

nachricht Plant inspiration could lead to flexible electronics
22.06.2017 | American Chemical Society

nachricht A rhodium-based catalyst for making organosilicon using less precious metal
22.06.2017 | Tokyo Institute of Technology

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

A new technique isolates neuronal activity during memory consolidation

22.06.2017 | Life Sciences

Plant inspiration could lead to flexible electronics

22.06.2017 | Materials Sciences

A rhodium-based catalyst for making organosilicon using less precious metal

22.06.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>