14 DAY TRIAL // It seems that the soldier of the future will become invincible due to the banal spider.
That's because the spider silk is not banal at all.
Spider silk is one of the stretchiest and strongest materials in nature, that's why bionic engineers have been searching to create artificial polymers achieving the performances of the spider's silk.
A team at Massachusetts Institute of Technology has recently designed a material achieving these desired qualities. These polymers, named nanocomposites, would be employed for tougher packaging materials and tear-resistant fabrics and biomedical devices.
The difficulty was achieving a material combining both qualities: strength and flexibility.
The secret behind the amazing properties of the spider silk was found to consist in the arrangement of the nano-crystalline reinforcement while the thread is being produced and in the way these tiny crystals are located towards and adhere strongly to the stretchy polymeric protein forming their surrounding matrix. "If you look closely at the structure of spider silk, it is filled with a lot of very small crystals," said Gareth McKinley, a professor of mechanical engineering. "It's highly reinforced."
So, the team figured out a way to mimic this nano-reinforced structure in a synthetic polymer (plastic).
While in previous researches, other teams heated and mixed molten plastics with reinforcing agents, the new approach focused on reinforcing polyurethane elastomer (a rubbery substance) solutions with nanosized clay discs (about 1 nanometer (1: 1,000,000 m thick) and 25 nm in diameter). "When you put them in the right solvent, these 'nanosized poker chips' all come apart," said McKinley.
The team embedded these discs in the polymer by first dissolving them into water, replaced after that the water with a solvent specific for the polymer and when the solvent was removed, resulted a "nanocomposite" of stiff clay discs spread throughout the stretchy matrix, which is now stronger and tougher.
The random distribution of the clay discs seems to be very important for the product's properties, providing reinforcement in every direction and very little distortion even at temperatures above 150 degrees Celsius. "Instead of a neatly packed arrangement, the process results in a very disorderly "jammed" structure," said McKinley.
Artificial "molecular composites" are extremely suitable for new lightweight membranes, but also for fuel cells and gas barriers. Besides very flexible body armors (clay is known for adsorbing bullet shock), the material could be for thinner, stronger packaging films for the soldiers' MREs (meals ready to eat) instead of the current thick and bulky packaging.
The nano-composites could impact also fabric production, as they can be used to make stretchy fibers similar to 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.