Extraction of delignified, cellulose-based fibers from natural plant material, and materials incorporating such fibers

A method comprising:

• (a) subjecting a piece of natural bamboo to one or more chemical treatments so as to remove lignin therefrom, at least one of the one or more chemical treatments comprising partial or full immersion in one or more chemical solutions, the natural bamboo having a microstructure with a plurality of cellulose-based macrofibers, parenchyma cells, and a matrix of lignin and hemicellulose that joins microfibrils of the cellulose-based macrofibers to the parenchyma cells, the one or more chemical treatments being effective to dissolve the matrix and break down the parenchyma cells such that the cellulose-based macrofibers are released;
• (b) after (a), extracting from the chemically-treated piece the plurality of cellulose-based macrofibers as individual, intact cellulose-based macrofibers separate and distinct from each other;
• (c) after (b), drying the cellulose-based macrofibers such that evaporation of water from each cellulose-based macrofiber causes self-densification thereof;
• and
• (d) after (c), embedding each cellulose-based macrofiber within a structural matrix to form a composite material,
• wherein, after (c):
• a content of lignin in each cellulose-based macrofiber is less than or equal to 4 wt %, each cellulose-based macrofiber has a moisture content less than or equal to 10 wt % and exhibits a tensile strength of at least 1 GPa, and
• each cellulose-based macrofiber has a length of at least 5 cm, a diameter of at least 100 μm, and a density of at least 1 g/cm3.