It's hard to believe that recycled paper could ever be transformed into a material stronger than steel, but scientists think they devised a method that might allow just that.
A team of Swedish and German researchers developed a procedure that spins tough filaments from small cellulose fibers, which is a plant material.
Artist's impression of the production of ultra-strong cellulose fibers: The cellulose nano fibrils flow through a water channel and become accelerated by the inflow of additional water jets from the sides. The acceleration lets all fibrils align with the direction of flow, finally locking together as a strong fiber. (DESY/Eberhard Reimann)
"Our filaments are stronger than both aluminium and steel per weight," lead author Fredrik Lundell from the Wallenberg Wood Science Center at the Royal Swedish Institute of Technology said in a statement. "The real challenge, however, is to make bio-based materials with extreme stiffness that can be used in wind turbine blades, for example. With further improvements, in particular increased fibril alignment, this will be possible."
Here's how it works:
For their method, the researchers took tiny, nanometre-sized cellulose fibrils and fed them together with water through a small channel. Two additional water jets coming in perpendicular from left and right accelerate the fibril flow. "Following the acceleration, all nano fibrils align themselves more or less parallel with the flow," explains co-author Dr. Stephan Roth from DESY, head of the experimental station P03 at PETRA III where the experiments took place. "Furthermore, salt is added to the outer streams. The salt makes the fibrils attach to each other, thereby locking the structure of the future filament."
Finally, the wet filaments are left to dry in air where they shrink to form a strong fibre. "Drying takes a few minutes in air," explains co-author Dr. Daniel Söderberg from KTH. "The resulting material is completely compatible with the biosphere, since the natural structure of the cellulose is maintained in the fibrils. Thus, it is biodegradable and compatible with human tissue."
The team used an ultra bright X-ray light to track the process and configuration of the fibrils at all stages of development.
Though they used nano filaments from fresh wood in this experiment, the study authors believe recycled paper could be a source as well.
"In principle, it should be possible to obtain fibrils from recycled paper also," Lundell said. "The potential of recycled material in this context needs further investigations."
The researchers also have to work on making he fibers longer for further applications. In the experiment, the samples they made were about 10 centimeters long.
This research was published in the journal Nature Communications.