The earliest proposal for engineering molecules toward a general method for fabricating devices to complex atomic specifications focused on engineering protein molecules. Although the concept of engineering proteins often brings to the imagination an implausible picture of trying to engineer meat into something stiff enough for making machinery, Drexler has pointed out that structural proteins are as stiff as engineering polymers. Indeed, this observation is further strengthened by the recent report of dipeptide nanospheres having (in the words of the abstract of the research paper) “a remarkable metallic-like Young’s modulus of up to 275 GPa.” The discovery is described on the POPSCI web site “New Nanospheres are the Stiffest Biological Materials Ever Created, Surpassing Kevlar“:
Printable body armor, better bulletproof glass, and tougher steel are just a few of the applications for a new materials technology developed by Israeli researchers. A team of scientists there have developed a transparent material made of self-assembling nanospheres that is the stiffest organic material ever created, surpassing the properties of stainless steel and even Kevlar.
Developed by researchers from the Weizmann Institute of Science and Tel Aviv University, the nanospheres are similar to the beta-amyloid proteins that make up the plaques found in the brains of people suffering from Alzheimer’s disease. But the new nanospheres are reinforced with an additional protective layer that makes them really, really strong.
And really, really small. They range in size from about 30 nanometers down to just two microns (by comparison, human hair averages something like 80 microns in diameter). But when assembled the material is extremely tough. In tests, only a diamond-tipped probe was able to dent the material, and then only by applying considerably more force that it takes to damage Kevlar.
The researchers cite applications ranging from “far-fetched ideas such as the ‘space elevator’ to realistic objects including reinforced plastic for medical implants or dental materials.” The nanospheres are formed by the self-assembly of Boc-Phe-Phe-OH peptides, which can also form tubular nanostructures. The researchers speculate that “the combination of the geometrically restricted π–π interactions between the aromatic moieties (Phe, phenylalanine) together with the planar nature of the amide bond may provide the unique mechanical properties so rarely observed in organic materials.”