Outside the body, biological molecules can have some surprising properties. For example, Dordick has found superstrong and lightweight proteins, and he is trying to stuff them into carbon nanotubes to create “self-healing” materials. Computer simulations show that when the nanotubes break under stress, they release the proteins, which aggregate and form an adhesive. If his simulations prove correct, these hybrid materials could become components in structures such as airplane wings. As cracks propagate over time, fractured nanotubes would release the adhesive, making repairs that would prolong the wing’s useful life.Many biological molecules such as DNA can spontaneously form complex structures in a process chemists call self-assembly. Researchers are hoping to take advantage of this natural process, using it to help construct complex nanostructures. New York University chemist Nadrian Seeman, for example, is using DNA as a scaffold for assembling nanoparticles of conducting materials.
Strands of DNA with attached nano-size particles could be “coded” to assemble spontaneously into a specific structure, for instance, the configuration of a circuit. “DNA is good for doing this because the molecule is so well understood, and it’s easy to control and predict what its final structure will be,” says Seeman. He and his colleagues have had success making two-dimensional structures out of DNA, and they are now working on making three-dimensional crystals. One of the ultimate goals is to use DNA’s knack for self-assembly as an easy and cheap way to fabricate nanoscale electronic materials or devices that could be used in ultrafast or ultrasmall computers.
Although it may be more than a decade before such bioelectronic materials are available, Dordick believes that relatively simple materials such as his self-cleaning or self-healing plastics could emerge in the next few years. “Things are moving quickly, and the number of people getting into this is increasing dramatically,” says Dordick. Still, researchers readily acknowledge that they are just beginning to explore the possibilities of new hybrid materials and that eventual applications remain uncertain. “We will all go in different directions because it’s such a rich field and because there are so many possibilities,” predicts Seeman.
But one thing seems certain. As material scientists continue to discover novel and interesting combinations of biological and nonbiological materials, it is a field that is coming alive.