Bacterial cellulose/silica hybrid fabricated by mimicking biocomposites

In plants such as grasses, rice, and sugar cane, biomineralizatin occurs such that amorphous silica is drawn from soil, transferred and deposited on polysaccharide matrix. In this study, by mimicking natural biomineralization in plants, a cellulose/silica hybrid was produced using bacterial cellulose (BC). BC hydro-gel was immersed in an aqueous solution of silanol derived from tetraethoxysilane (TEOS), and silanol was then converted into silica in the BC hydro-gel matrix. By pressing the BC hydro-gels and hybrids at 120 °C and 1–2 MPa, water-free translucent sheets were obtained. In the leaves of rice plants, large silica bodies (μm order) were embedded in the polysaccharide matrix, whereas in the BC/silica hybrids, nano scale silica was embedded between the micro fibrils of the BC matrix. Reflecting this structure, the modulus of elasticity and tensile strength of dry BC/silica hybrid improved to 17 GPa at 25 °C and 185 MPa, respectively. In the case of rice plants, the modulus was 3.5 GPa at 25 °C and the tensile strength was 25–88 MPa, suggesting a weaker structure than in BC hybrid.