Strong, tough, anisotropic, flexible, and transparent bamboo films

Bamboo has higher strength, better toughness, and a shorter growth cycle than wood. It is of great significance to use top-down nanotechnology to construct high-performance bamboo film (BF) instead of petroleum-based plastic film. However, bamboo lacks lateral cell tissues, and its structure is prone to disintegration when the components are removed. Herein, slice bamboo veneers (SBV) were used as building blocks, and a sequential process of alkali pretreatment-crosslinking-delignification-compression densification was conducted to fabricate the high-performance BF. The oriented arrangement of nanofibers, highly dense microstructure, and a large number of hydrogen bonds between cellulose microfibrils endowed BF with anisotropic and excellent mechanical and optical properties. The longitudinal tensile strength and toughness of the prepared BF were 656.6 MPa and 33.7 MJ m−3, respectively, and its light transmittance and haze were 70.2% and 88.1%, respectively. In addition, BF has good thermal insulation with a thermal conductivity of 0.0857 W m−1 K−1. The combined characteristics of BF, including high strength, high toughness, flexibility, anisotropy, high optical transmittance, and thermal insulation, make them suitable to be applied as optoelectronic substrates, insulating building materials, and green packaging materials.