The fibres made of nanocomposites, a polymer, could be used to strengthen and toughen packaging materials and develop tear-resistant fabrics or biomedical devices, according to researchers at MIT's Institute for Soldier Nanotechnologies (ISN).

Till now, engineers have been able to create materials that are either very strong or very stretchy. Attaining both the qualities in the same material was difficult, but the new fibre combines both the qualities.

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," said Professor Gareth McKinley, a professor of mechanical engineering, who conducted the research along with graduate student Shawna Liff and postdoctoral researcher Nitin Kumar.

However, after numerous unsuccessful attempts of making the fibres by heating and mixing molten plastics with reinforcing agents, the research team 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 nanometre, or a billionth of a meter thick and 25 nanometres 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 Prof. McKinley.

The disorderly "jammed" structure, according to Prof. McKinley, provides reinforcement to the nanocomposite material in every direction, and the material exhibits very little distortion even when heated to temperatures above 150 degrees Celsius.

Prof. Evangelos Manias of the University of Pennsylvania, said, "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," he wrote in the January issue of Nature Materials.

According to the study, fabric companies and the US military have expressed interest in the new materials, which can be used to make fibres similar to stretchy compounds such as nylon or Lycra.