A new study, published in the journal of American Chemical Society (ACS Nano), reveals a new bio-based material generated by researchers at KTH Royal Institute of Technology in Stockholm, Sweden, that is stronger than all currently existing bio-based materials including wood and spider silk. The material was created using a new method that recreates nature’s ability to arrange cellulose nanofibres into macroscale arrangements.
In nature, the nanoscale building blocks of some materials have unique mechanical properties caused by a defect-free molecular structure. However, up to now, recreating these mechanical properties for macroscopic materials has always been problematic because it requires arranging these building blocks into the appropriate multiscale patterns while dealing with the defects that arise in these larger scales.
"Lately, scientists have been seeking ideas of mimicking natural materials’ architecture based on engineering design principles, typically called “bioinspired assembly”. An overarching challenge in structural materials fabrication is to translate the extraordinary mechanical properties of nanoscale building blocks," states the paper.
In this study, KTH researchers worked with cellulose nanofibres (CNF), the building blocks of plants, to overcome these issues. The scientists chose CNFs because they are one of nature's most abundant structural elements and have great mechanical stiffness and strength.
Impressive strength and stiffness
The result was the creation of larger yet still lightweight materials that also exhibited impressive strength and stiffness. “The bio-based nanocellulose fibers fabricated here are 8 times stiffer and have strengths higher than natural dragline spider silk fibers, generally considered to be the strongest bio-based material,” said corresponding author Daniel Söderberg, a researcher at KTH Royal Institute of Technology.
“The specific strength is exceeding that of metals, alloys, ceramics and E-glass fibers.”
“The specific strength is exceeding that of metals, alloys, ceramics and E-glass fibers,” Söderberg added.
The new material is the result of a complex process which sees nanofibres suspended in water in a 1 mm wide channel milled in stainless steel while their flow is monitored.
Flows of deionized water and low pH water are then used to align the nanofibres in the correct direction so that the supramolecular interactions between CNFs arrange themselves into the right state. “Here, we report the flow-assisted organization of CNFs into macroscale fibers with nearly perfect unidirectional alignment,” stated the study.
This new lightweight high-performance material is also eco-friendly, energy-efficient and comes from sustainable renewable resources. Future applications for the bio-material could range from the production of automobiles and aircraft to furniture and other products.
“This discovery is made possible by understanding and controlling the key fundamental parameters essential for perfect nanostructuring, such as particle size, interactions, alignment, diffusion, network formation and assembly,” concluded Söderberg.
Although revolutionary, this discovery is not entirely new. Variations of CNF have been used since 2015 in the manufacturing of products such as disposable diapers, ballpoint pen ink, audio speakers and even toilet cleaner.