Larissa G. Franca, Paloma L. dos Santos, Piotr Pander, Marília G. B. Cabral, Rodrigo Cristiano, Thiago Cazati, Andrew P. Monkman, Harald Bock, and Juliana Eccher. Submitted. “Delayed Fluorescence by Triplet–Triplet Annihilation from Columnar Liquid Crystal Films.” ACS Applied Electronic Materials, Pp. null. Publisher's Version
Cleidineia Cavalcante Costa, Ludmila Marotta Mapa, Ana Carolina Kelmer, Sukarno Olavo Ferreira, and Rodrigo Fernando Bianchi. Submitted. “New insight into natural fiber-reinforced polymer composites as pressure sensors: Experiment, theory, and application.” Polymer Composites, n/a, n/a. Publisher's VersionAbstract
Abstract Research in hybrid and flexible natural fiber-reinforced polymer composites has included advances in innovative and environmentally sustainable devices. However, in practice, controversies still exist regarding the relationship between electrical and materials performance targets in a system design context. This work aimed to investigate the alternating conductivity of a novel pressure sensor based on semiconducting polyaniline (PANI)-coated vegetable fiber (VF, Euterpe oleracea Mart., Acai) in silicone polydimethylsiloxane (PDMS) rubber. We used alternating electrical conductivity measurements, σ*(ω) ∝ ωs (frequency range—ω from 1 Hz to 10 MHz; s   0.6), to adjust the optimal operating frequency region to enhance the pressure sensing performance of the PDMS-PANI-VF composites. A generalized effective-medium approach to the pressure-induced conductivity in terms of loading pressure, percolation regime, and the interpolation between Bruggeman's symmetric and asymmetric media theories was obtained. We have found a solution for inducing percolation in composites with a low concentration of fiber inclusions by uniaxial pressure (P), characterized by the expression σ ∝ (P−P0)t (0 ≤ t ≤ 4.0, 0 ≤ P0 ≤ 250 kPa). The sensor demonstrates maximum sensitivity of 1.5 Pa−1 in the operating electrical frequency from 1 to 100 Hz, and a wide linearity range from 0 to 250 kPa. The result provides new insight into the AC universality, s, and t behaviors of natural fiber-reinforced polymer composites to enhance pressure sensitivity of a new concept and technology for resource-efficiency optimization of sustainable environmental devices.