Nature often produces materials and processes that guide scientists in their pursuit of innovation. One of the latest such examples comes in the form of a synthetic spider silk developed by researchers at Washington University in St. Louis.
According to the researchers, who published their findings in the journal ACS Nano, their artificial version of the silk fiber can surpass the strength and toughness of the real thing.
The researchers chose to model their new material on spider silk as it's known to be a highly robust material with impressive tensile strength. Their new material is the latest iteration of a fiber first developed by the same team back in 2018 which also used natural spider silk as a reference point.
Their work isn't the only research to draw inspiration from spiders. This month, research was also released showing how venom of the Fraser Island (K’gari) funnel-web spider could prevent damage caused by a heart attack.
In order to develop their material, the Washington University scientists genetically engineered bacteria in a lab so that they would produce amyloid silk hybrid proteins. One of the keys to the latest version of the researchers' silk material was finding how to add the required amount of nanocrystals to the synthetic fiber.
"Spiders have figured out how to spin fibers with a desirable amount of nanocrystals," Fuzhong Zhang, lead researcher on the study, explained in a press statement. "But when humans use artificial spinning processes, the amount of nanocrystals in a synthetic silk fiber is often lower than its natural counterpart."
Finding the right nanocrystal balance
In order to improve the nanocrystal count in their material, the researchers added new amyloid sequences that have a higher tendency to form the required nanocrystals.
The Washington University researchers' bacteria ultimately produced a hybrid polymeric amyloid protein with 128 repeating units. While that constitutes fewer units than the 192 in the team's previous work, the researchers say the added nanocrystals more than make up for the resulting loss in strength.
In their tests, the researchers showed that the 128-repeat proteins resulted in "a fiber with gigapascal strength (a measure of how much force is needed to break a fiber of fixed diameter), which is stronger than common steel."
At approximately 1 Gigapascal (GPa) in strength, the fiber strength is also higher than some natural spider silk fibers and even Kevlar. The researchers also measured an average toughness of around 161 Megajoules per m3 for their material, making it tougher than some natural spider silks.
Crucially, the team said there are still thousands of amyloid sequences they can explore, meaning their material will likely be improved in the future.