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- Light shutters from nanocrystalline cellulose rods in a nematic liquid crystalPublication . Geng, Yong; Brogueira, Pedro; Figueirinhas, João; Godinho, Maria Helena; Almeida, Pedro L.This work reports a recently developed electro-optical (EO) device that can potentially be used as a light shutter or a privacy window. By using nanocrystalline cellulose rods, we were able to improve some of the most relevant parameters characterising the EO behaviour. A brief description of the proposed working mechanism for these devices is presented, and numerical simulations based on this mechanism of both the optical transmission and the cells' electrical capacitance are compared with the obtained results, validating the underlying working model considered.
- Structural Color and Iridescence in Transparent Sheared Cellulosic FilmsPublication . Fernandes, Susete N.; Geng, Yong; Vignolini, Silvia; Glover, Beverley J.; Trindade, Ana C.; Canejo, João P.; Almeida, Pedro L.; Brogueira, Pedro; Godinho, Maria HelenaShear transparent cellulose free-standing thin films can develop iridescence similar to that found in petals of the tulip Queen of the Night. The iridescence of the film arises from the modulation of the surface into bands periodically spread perpendicular to the shear direction. Small amounts of nanocrystalline cellulose (NCC) rods in the precursor liquid-crystalline solutions do not disturb the optical properties of the solutions but enhance the mechanical characteristics of the films and affects their iridescence. Smaller bands periodicity, not affected by the NCC rods, slightly deviated from the shear direction is also observed. NCCs are crucial to tune and understand the film's surface features formation. Our findings could lead to new materials for application in soft reflective screens and devices.