Nanopaper made of gently processed natural cellulose nanofibers is found to have remarkable strength; it has a tensile strength almost equaling that of structural steel.
Lars Berglund from the Swedish Royal Institute of Technology in Stockholm, Sweden found that the mechanical processes used to pulp wood damages the natural fibers, weakening them. Berglund developed a process to extract the fibers, keeping their properties intact.
Mechanical testing shows it has a tensile strength of 214 megapascals, making it stronger than cast iron (130 MPa) and nearly as strong as structural steel used in buildings and bridges (250 MPa). Normal paper is flimsy; it has a tensile strength less than 1 MPa. The tests used strips 40 millimeters long by 5mm wide and about 50 micrometers thick.
Science fiction readers may recall the material used in Jules Verne's 1866 classic Robur the Conqueror.