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Electroactive polymers (EAPs), materials that present size/shape alteration in response to an electrical stimulus, are currently being explored regarding advanced smart devices, namely robotics, valves, soft actuators, artificial muscles, and electromechanical sensors. They are generally prepared through conventional techniques (e.g., solvent casting and free-radical polymerization). However, non-conventional processes such as those included in additive manufacturing (AM) are emerging as a novel approach to tune and enhance the electromechanical properties of EAPs to expand the scope of areas for this class of electro-responsive material. This review aims to summarize the published work (from the last five years) in developing EAPs either by conventional or non-conventional polymer processing approaches. The technology behind each processing technique is discussed as well as the main mechanism behind the electromechanical response. The most common polymer-based materials used in the design of current EAPs are reviewed. Therefore, the main conclusions and future trends regarding EAPs obtained by conventional and non-conventional technologies are also given.

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The main objective of this work was the development and characterization of sustainable electro-responsive ionic liquid-based cationic copolymers. For this purpose degradable semi-interpenetrating polymer networks (s-IPNs) based on starch and on ion-conducting cationic copolymers of 2-hydroxyethyl methacrylate (HEMA) and 1-butyl-3-vinylimidazolium chloride (BVImCl), cross-linked with N,N′-methylenebis­(acrylamide) (MBA), were synthesized by following principles of green chemistry. Cross-linked poly­(HEMA-co-BVImCl) copolymers were also prepared for comparison. The resulting cationic hydrogels (copolymer and s-IPNs) were characterized in terms of their physicochemical, thermomechanical, morphological, and electrochemical properties, as well as in terms of cell viability and proliferation against fibroblast cells. Furthermore, the electro-assisted sorption/release capacity of the prepared hydrogels toward l-tryptophan (used as a model biomolecule) was also studied at different applied DC voltages (0, 2, 5, and 100 V). Results demonstrated that the properties of the synthesized hydrogels can be tuned, depending on their relative chemical composition, presenting electronic conductivity and ionic conductivity values in the 0.1 to 5.2 S cm–1 range, and complex shear modulus in the 0.6 to 6.4 MPa range. The sorption/release capacity of the s-IPNs after 3 h at 25 °C can also be modulated between 2.5 and 70% and 4.5 and 40%, depending on the applied DC voltage and/or sorption/release medium. Finally, none of the synthesized cationic hydrogels induced fibroblast cells lysis, although s-IPNs had a lower impact on cell proliferation than poly­(HEMA-co-BVImCl) copolymers, indicating a favorable effect of starch on the biocompatibility of the synthesized s-IPNs. The designed cationic hydrogels could be useful for the development of efficient, stable, degradable and cheaper soft and multiresponsive platforms with potential applications in bioseparation processes, wastewater treatment systems (e.g., pharmaceutical), biomedical devices (e.g., sustained delivery of specific charged-biomolecules), and nonleaching electrochemical devices.

Tissue engineering is a fascinating branch of science that aims to develop strategies to respond to tissue/organ damage with the slightest biological rejection. It is currently known that electric cues...

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This work studied the influence of hydrogel’s physical properties (geometry and hierarchical roughness) on the in vitro sorption/release profiles of molecules. To achieve this goal, chitosan (CS) solutions were cast in 3D-printed (3DP) molds presenting intricate shapes (cubic and half-spherical with/without macro surface roughness) and further immersed in alkaline solutions of NaOH and NaCl. The resulting physically crosslinked hydrogels were mechanically stable in aqueous environments and successfully presented the shapes and geometries imparted by the 3DP molds. Sorption and release profiles were evaluated using methyl orange (MO) and paracetamol (PMOL) as model molecules, respectively. Results revealed that distinct MO sorption/PMOL release profiles were obtained according to the sample’s shape and presence/absence of hierarchical roughness. MO sorption capacity of CS samples presented both dependencies of hierarchical surface and geometry parameters. Hence, cubic samples without a hierarchical surface presented the highest (up to 1.2 × greater) dye removal capacity. Moreover, PMOL release measurements were more dependent on the surface area of hydrogels, where semi-spherical samples with hierarchical roughness presented the fastest (~1.13 × faster) drug delivery profiles. This work demonstrates that indirect 3DP (via fused filament fabrication (FFF) technology) could be a simple strategy to obtain hydrogels with distinct sorption/release profiles.

RESUMO -Visando uma futura análise do processo de secagem, este trabalho teve como objetivo obter as curvas de isotermas de dessorção de sementes de azevém (Lolium multiflorum L.) nas temperaras de 40 e 60 °C. Os experimentos foram feitos através do método gravimétrico estático com o uso soluções de ácido sulfúrico em onze diferentes concentrações que garantiram a variação da umidade relativa de 5 a 89 %. O sistema foi armazenado em estufa até atingir o equilíbrio mássico no décimo quarto dia. Os dados experimentais obtidos foram ajustados aos modelos matemáticos de BET, GAB, Oswin, Peleg e Henderson. Os resultados obtidos mostraram que os valores da umidade de equilíbrio possuem uma forte dependência com a temperatura. Também verificou-se que os modelo matemático que melhor se ajustou aos dados experimentais foi o de Oswin, com coeficientes de determinação acima de 0,99. Segundo Mota et al.;(1981), no Rio Grande do Sul, aproximadamente 61 % da cobertura vegetal é composta por pastagens nativas, que apresentam crescimento vegetativo nas estações quentes. Porém, nas estações frias ocorre uma redução na produção e torna-se necessário a implementação de forrageiras. Uma alternativa para suprir esta demanda é o azevém (Lolium multiflorum L.), uma forrageira de clima temperado e com boa adaptabilidade às condições climáticas do estado. Palavras chave: FORRAGEIRA, SECAGEM, MODELOS MATEMÁTICOS INTRODUÇÃOApesar disto, o azevém (Lolium multiflorum L.) apresenta um fator limitante para a implementação de pastagens devido ao baixo índice de germinação das sementes (faixa de 60 a 70 %). Isto ocorre devido à baixa qualidade das sementes, fato que está vinculado ao processo de beneficiamento, que tem como etapa limitante a secagem.De acordo com Strumillo e Kudra (1986) a secagem é definida como a remoção de líquido de um sólido por evaporação. Nos processos de secagem, o material úmido é colocado em contato com o ar insaturado e como resultado disso se tem uma transferência simultânea de calor e de massa com diminuição do conteúdo de umidade do material e umidificação do ar. Assim, dois estágios definem o processo total de secagem,