Grown Ultrathin Bacterial Cellulose Mats for Optical Applications

A facile and effective method is described for the biosynthesis of ultrathin bacterial cellulose (BC) mats, which are green, inexpensive, lightweight, and flexible. Physical properties studied include thickness, morphology, reflectance, transmittance, and crystallinity index. BC mat thickness was varied by controlling the depth of the culture broth so that films with predictable thickness, between 113 and 1114 nm, were produced. These BC films have similar fiber morphology to corresponding mm thick BC films prepared under static culture conditions. To increase BC film hydrophobicity, surface trihexylsilylated BC (THSBC) mats with DSavg 0.015 were prepared. Both native and THSBC mats were investigated as antireflection coatings for silicon substrates. The 328 +/- 42 nm thick BC mat demonstrated broadband, interference type antireflection over a spectral range of 500-1800 nm. Different reflection properties obtained as a function of BC film orientation reveals that engineered density gradients can be used to manipulate BC optical properties. Thus, optical quality and environmental friendly ultrathin BC films are promising biomaterials for next-generation optoelectronic devices.