RESUMO
Electronic flexible devices are prone to degrade their electrical performance or lose functionality when subjected to deformations. Brittle fracture is a common damaging effect observed in devices composed of low-thickness layered materials stacked onto a flexible substrate by dissimilar mechanical properties interaction. This work studies the mechanical behavior of Organic Flexible Solar Cells (OFSC) with a heterostructure PET/ITO/P3HT:PCBM/Ag subjected to uniaxial displacements through an experimental and numeric point of view. Experimental showed that damage proceeds in two ways. First, the formation of a grid crack pattern begins at the ITO layer, and second, the delamination in the ITO/P3HT:PCBM interface. The numerical model analyzed the force and displacements and the absorption/dissipation of strain energy on layers and interfaces of the device. The comparison of the global Young's module for experimental and numeric studies validated the numeric analysis, with results of 4.16 ± 0.05 GPa for experimental and 4.36 ± 0.15 GPa for numeric. Additionally, the model associates the ITO layer with the highest strain energy dissipation or the most prone to failure, which agrees with the experiments. Then, the model successfully predicts the mechanical behavior of OFSC and represents a valuable tool for studying flexible devices and predicting the appearance of mechanical damage when subjected to uniaxial deformations, even being able to avoid potential damage changing parameters such as the thickness of the layers.
RESUMO
Dinophysis acuta produces diarrhetic shellfish poisoning (DSP) toxins and pectenotoxins (PTX). It blooms in thermally-stratified shelf waters in late summer in temperate to cold temperate latitudes. Despite its major contribution to shellfish harvesting bans, little effort has been devoted to study its population dynamics in Chilean Patagonia. In 2017-2018, mesoscale distribution of harmful algal species (75 monitoring stations) revealed the initiation (late spring) and seasonal growth of a dense D. acuta population in the Aysén region, with maximal values at Puyuhuapi Fjord (PF). Vertical phytoplankton distribution and fine-resolution measurements of physical parameters along a 25-km transect in February 16th identified a 15-km (horizontal extension) subsurface thin layer of D. acuta from 4 to 8 m depth. This layer, disrupted at the confluence of PF with the Magdalena Sound, peaked at the top of the pycnocline (6 m, 15.9 °C, 23.4 psu) where static stability was maximal. By February 22nd, it deepened (8 m, 15.5 °C; 23.62 psu) following the excursions of the pycnocline and reached the highest density ever recorded (664 × 103 cells L-1) for this species. Dinophysis acuta was the dominant Dinophysis species in all microplankton net-tows/bottle samples; they all contained DSP toxins (OA, DTX-1) and PTX-2. Modeled flushing rates showed that Puyuhuapi, the only fjord in the area with 2 connections with the open sea, had the highest water residence time. Long term climate variability in the Southern hemisphere showed the effects of a Southern Annular Mode (SAM) in positive mode (+1.1 hPa) overwhelming a moderate La Niña. These effects included positive spring precipitation anomalies with enhanced salinity gradients and summer drought with positive anomalies in air (+1 °C) and sea surface (+2 °C) temperature. Locally, persistent thermal stratification in PF seemed to provide an optimal physical habitat for initiation and bloom development of D. acuta. Thus, in summer 2018, a favourable combination of meteorological and hydrographic processes of multiple scales created conditions that promoted the development of a widespread bloom of D. acuta with its epicentre at the head of Puyuhuapi fjord.