SAN JOSE, Calif. The Massachusetts Institute of Technology (MIT) claims that it has devised a way to produce a material that mimics the stretchy and strong properties of spider silk for use in fuel-cell cells, medical devices, military products and even Spider-Man-like fabrics.
The materials, known as polymeric nanocomposites, are weaving a web of interest for use in packaging materials, tear-resistant fabrics and biomedical devices. Another possible use is membranes for fuel cells.
This research was funded by the U.S. Army through MIT's Institute for Soldier Nanotechnologies and by the National Science Foundation.
The U.S. military is interested in such materials for use in future applications, such as tear-resistant films or other body-armor components. The military is also interested in these materials 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, according to MIT.
Engineers are already able to create materials that are either strong or stretchy, but it has been difficult to achieve both 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.
The silk's strength and flexibility comes from this nanoscale crystalline reinforcement and from the way these tiny crystals are oriented. The crystals adhere to the stretchy protein that forms its surrounding polymeric matrix.
To develop the materials, MIT started with tiny clay discs at about 1-nm 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," according to MIT.
The researchers developed a process to embed these clay chips in a rubbery polymer by 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. The clay platelets are distributed randomly in the material.
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.