Spider silk has long held the title of strongest natural biomaterial, so scientists have been trying to harness it, mimic it and even improve on the recipe for years. Now, researchers at the KTH Royal Institute of Technology have developed a new biomaterial out of wood nanofibers that steals the strength record.

Wood is one of nature's sturdiest materials, but that doesn't mean it can't be made even better. Researchers recently "densified" the material to make what they call "super wood," and previous work from the KTH team made wood fibers as strong as steel.

Key to both the previous and current KTH work are what are known as cellulose nanofibrils (CNFs). These tiny fibers come together to make the cell walls of wood strong and stiff, and working out how to assemble them on the nanoscale has helped the team build a stronger material.

The researchers used a flow-assisted assembly technique that involved suspending nanofibers in water, in channels just 1 mm wide. Deionized and low pH water flows through, which helps the CNFs align in the right direction and self-organize into tightly-packed bundles. The resulting material is strong, stiff, lightweight and large enough for practical use, creating what the team says is the strongest biomaterial made so far.

"The bio-based nanocellulose fibers fabricated here are eight times stiffer and have strengths higher than natural dragline spider silk fibers, generally considered to be the strongest bio-based material," says Daniel Söderberg, corresponding author of the study. "The specific strength is exceeding that of metals, alloys, ceramics and E-glass fibres."

In numbers, the team measured the tensile stiffness of the material to be 86 gigapascals, and its tensile strength to be 1.57 gigapascals. Even the weakest individual fiber they made was found to be stronger than previously-created CNF fibers.

The researchers say the technique could be used to make strong, lightweight materials for building planes, cars, bikes and furniture. It could also help assemble other nanofibers too, such as carbon tubes.

The research was published in the journal ACS Nano.