Reversible wettability control of self-assembled TiO2 scaffolds on bacterial cellulose from superhydrophobicity to superhydrophilicity

Superhydrophobic TiO2/BC nanocomposites with reversibly wettability surfaces were fabricated by a simple self-anchoring method on the natural bacterial cellulose (BC) fibers. Under UV light irradiation, the organosilicon-modified TiO2/BC surfaces (M-TiO2/BC) exhibited a surface transition from superhydrophobic (water contact angle of 158° ± 1°, sliding angle of 3°) to superhydrophilic (water contact angle of 10° ± 1°) within only 20 min. Besides pure water, for different kinds of liquid including milk, orange juice, synthetic blood, and seawater, M-TiO2/BC exhibited excellent self-clean performance. The XRD, SEM, TEM, FTIR, TGA, BET and XPS analyses were employed to characterize the morphological features and surface chemistry of the M-TiO2/BC films enclosed by different amounts of TiO2 nanoparticles with the average size of 2.85 nm. Furthermore, the effect of deposition time and Ti precursor concentration on the superhydrophobicity was carefully compared and analyzed. Interestingly, the UV light source with the maximal peak at 365 nm (UVA) exhibited better performance of reversible switching than the light source with the maximal peak at 245 nm (UVC). After three successive recycles, the M-TiO2/BC films remained stable for the UV–thermal induced reversible wettability. The simple and self-anchored synthesis of TiO2/BC hierarchical structures is believed to be helpful for the further expansion of multifunctional soft materials.