Cellulose Nanocrystals and Their Use in Electrical Systems

Cellulose is the most abundant natural polymer that is a biodegradable-renewable resource and plays a structural role in cell walls of plants. (C 6H 10O 5) n , or Cellulose is available from plants, fungi, bacteria, and various other sources. Cellulose nanocrystals (CNCs) are biomaterials that can self-assemble into liquid crystals, much like Liquid crystal displays (LCDs) used in electronic screens on many types of devices. With evaporation-induced self-assembly (EISA), CNCs can be orderly arranged to form a polarized optical grating which functions like a prism and is manifest in the formation of rainbow-colored light when shined by sunlight. The remarkable rainbow is revealed in the reflected sunlight which has even more intriguing polarization, rotating helically in a certain direction. Unfortunately, the resulting CNC film from EISA is rather rigid, stiff and not amenable to mechanical force. Hence, its optical characteristics can hardly be tuned. We investigate the fabrication of a composite that is flexible like rubber while maintaining the optical quality of CNCs. We study the formation of the composite by mixing CNCs with an elastomer (e.g. polyurethane found in caulking) and experiment with optimizing its fabrication by adjusting various parameters and enhancing CNCs alignment. With flexibility of the composite, the CNCs properties can be adjusted by stretching the material. Such a composite can be a building block for sensors. For instance, a mechanical sensor or voltage sensor provides visual output in terms of changes in color. We are looking forward to applying what we have learned to design composites to aid in creating optical modulators and applications in flexible electronics