Biodegradable and Biocompatible Silk Fibroin for Optical Applications
This study presents nanopatterned silk fibroin films that were fabricated using soft lithography and nanoimprinting to replicate patterns from diffraction gratings. These film’s optics were analyzed based on their light scattering potential as well as their transmittance and transmission haze using a laser light, spectrometer, and UV-Vis spectrophotometer, respectively. The patterned fibroin films all displayed similar light scattering patterns to their master patterns with some transmission haze. When using the spectrometer to measure samples, those made without any nanostructure displayed transmission of 90% and over, while those with patterns depended on the structure used. The denser a structure, like the mesh structure used, resulted in lower transmission (~70%), while those with a less dense linear structure displayed higher transmission (~80%). This agreed well with transmission measurements of patterned polydimethylsiloxane (PDMS) molds created to fabricate the patterned films. When using the more complex spectrophotometer device to measure the transmission, the light transmitted by all films was found to be much higher, over 90%. This is because the spectrophotometer can measure the total transmission, while the spectrometer apparatus using optical fibers can not collect light that is scattered beyond the diameter of the fiber. For the transmission haze, samples displayed high haze of over 65% across a 400-850 nm range, with nanostructures adding additional haze, up to 70% with a mesh structure. Based on this analysis, a new direction is open to combine transparent fibroin films with high haze with either solar cells to act as an anti-reflection (AR) coating with its light scattering abilities or as a short-range, bio-dissolvable implantable device for photodynamic therapy (PDT) to act as an optical diffuser by combining the film with a degummed silk fiber that can act as an optical waveguide. These technologies can give new arrangements for bio-photonic devices to be used in photovoltaics (PV) or medical treatments that have the the advantage of being totally biodegradable and biocompatible making them safe for the environment and human bodies.