Scalable, Flexible, and Highly Transmission Sweet Sorghum Film

As a nonfood crop, sweet sorghum has been extensively utilized for sugar production and biomass energy conversion. However, industrial production generates a significant amount of sweet sorghum skin. Although paper and cellulose-based films are commonly prepared through a bottom-up approach to capitalize on their abundant cellulose content. The bottom-up approach often involves the use of substantial quantities of chemical reagents, thereby posing a serious threat to environmental safety. In this study, inspired by the arrangement of traditional Chinese house roof tiles, we employed a stacking and hot-pressing preparation strategy to transform sweet sorghum skins into flexible sweet sorghum films (SF). SF retained the high degree of orientation of cellulose while obtaining high strength and toughness along with excellent light transmission properties. In particular, the mechanical properties of SF in the direction parallel to the fibers are exceptionally remarkable. The tensile strength measured 796.4 MPa, while the toughness stands at 7.63 MJ/m3. Additionally, SF exhibited outstanding optical characteristics, boasting a remarkable light transmission of 78% and a haze of 60%. Moreover, we established the feasibility of utilizing SF as a functional material for various applications, showcasing its potential for optical management, smart wearables, and electronic devices. Importantly, the successful preparation of large-size SF unlocked possibilities for their widespread and large-scale utilization, thus making a valuable contribution to environmental sustainability.