Artificially Designed Fibers Are Tougher Than Kevlar

Engineers at Washington University in St. Louis have designed a new amyloid silk hybrid protein and produced the protein in engineered bacteria. Fibers resulting from the material are stronger and tougher than natural spider silks. Spider silks are known to be one of the strongest and toughest materials on Earth. The artificial silk is called "polymetric amyloid" fiber.

The fibers are produced by bacteria that were genetically engineered in the laboratory of Professor Fuzhong Zhang. Zhang has worked with spider silk in the past, and in 2018 his laboratory engineered bacteria that produced a recombinant spider silk with performance similar to natural counterparts in all important mechanical properties. Zhang said that he wondered if the team could create something better than spider silk using the synthetic technology platform they developed.

The team had to overcome one significant challenge associated with recombinant spider silk fiber without introducing significant modifications to create the β-nanocrystals, which is the main component of natural spider silk, and gives the material its strength. To overcome that challenge, the team created different polymetric amyloid proteins using three well-studied amyloid sequences.

Proteins resulting from the process have less repetitive amino acid sequences than spider silk making them easier for bacteria to produce. Ultimately, the process produced a hybrid polymetric amyloid protein with 128 repeating units. The longer the protein, the stronger and tougher the resulting fibers.

Researchers note that the 128-repeat proteins resulted in a fiber with a gigapascal strength higher than common steel. It was also higher in toughness than Kevlar and all previous recombinant silk fibers. The team says that it's just getting started in its research, and their discovery demonstrates they can engineer biology to produce materials able to beat the best materials available in nature.