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- Efeito das condições de cultura da microalga Chlorella vulgaris sobre a produtividade e produção de carotenoidesPublication . Parente, João Miguel Nunes; Simões, Rogério Manuel dos Santos; Coutinho, PaulaO aumento da população mundial tem levado ao aumento do consumo de recursos, incluindo os energéticos e alimentares. Esta pressão torna urgente explorar e implementar alternativas assentes numa economia de base biológica, mais amiga do ambiente e sustentáveis. As microalgas, que podem ser usadas para alimentação humana e animal e ainda como fontes de biocombustíveis, constituem uma matéria-prima alternativa para as economias de base biológica. Apesar destes microrganismos apresentarem muitas vantagens como “fábrica biológica”, persiste a necessidade de melhorar e otimizar os processos de produção de biomassa, recolha de biomassa e extração de componentes de elevado valor acrescentado. Nesta dissertação, foram realizados estudos nestas diferentes vertentes. Em relação à produção da biomassa (Chlorella vulgaris), utilizaram-se- reatores air-lift cilíndricos, flat-plate em modo descontínuo e em modo contínuo, sob diferentes condições de operação, concluindo-se que os reatores em modo contínuo obtiveram um melhor crescimento específico da biomassa (0,2 dia-1), quando comparados com os reatores em descontínuo (0,084 dia-1). No que respeita à recolha da biomassa produzida, explorou-se o potencial do amido catiónico, tendo-se comparado o seu desempenho com um floculante sintético, o polyDADMAC. Os ensaios mostraram que o amido catiónico pode ser uma boa alternativa ao uso de floculantes sintéticos. Na extração dos pigmentos foi usado um método referido na literatura, e fez-se a respetiva quantificação e caraterização com recurso à cromatografia liquida acoplada à espectrometria de massa (LC-MS). Os melhores resultados foram obtidos a partir do reator Flat-plate em modo de operação contínuo, tendo-se obtido 3,8 e 1,57 mg carotenoides/g (matéria seca) de luteína e ß-caroteno, respetivamente. Os resultados desta dissertação representam uma contribuição para a otimização da produção de microalgas e extração de produtos de valor acrescentado, reduzindo os custos de operação no futuro.
- Smart textiles for health monitoring in industrial environments: a framework for wearable sensor integrationPublication . Vilarinho, Bruna Abreu; Vieira, Andre; Nunes-Pereira, João; Parente, João Miguel Nunes; Pires, Ivan Miguel Serrano ; Velez, Fernando J.The occupational health and safety of workers in industrial plants are increasingly compromised through exposure to thermal, physical, and psychological stressors. Wearable sensors embedded in garments have been introduced as a promising technology for real-time, continuous health monitoring without compromising workers' mobility or comfort. This paper reviews recent literature on wearable sensor technologies embedded in textiles, with a focus on their applicability in industrial settings. The paper identifies the key physiological parameters commonly monitored (e.g., heart rate, skin temperature, respiratory rate, and skin conductance), the materials and sensor types used, as well as the methods of integration into garments. Based on the findings, a conceptual model for a smart textile monitoring system tailored to industrial workers is proposed. The aim is to support the development of ergonomic, accessible, unobtrusive, and effective solutions that promote occupational health and prevent work-related illnesses.
- CFRP laminates enhanced with graphene nanoparticles in multifunctional applicationsPublication . Parente, J.M.; Carvalho, Ana; Nunes-Pereira, João; Reis, Paulo; Pereira Silva, AIn automobile, aeronautical, aerospace, sports and energy fields, there has been an increase of the use of carbon fibre reinforced polymers (CFRP) due their considerable advantages, such as, low weight, static and fatigue strength as well as corrosion resistance1. The addition of nanoparticles, in particular carbon allotropes, like graphene nanoplatelets (GNP) or carbon nanotubes (CNT) allow not only enhanced mechanical performance2, but also can alter the electrical conductivity response of the CFRP composite system3. While the carbon fibre is conductive, the epoxy is not conductive, and the aleatory dispersion of the nanoparticles should introduce in the composite system considerable changes in electric conductivity. The present work intends to study the effect of GNP on the mechanical response of composite laminates, and for this purpose CFRP laminates with and without GNP were manufactured and characterized in terms of flexural and viscoelastic behaviour. Furthermore, electric conductivity tests were performed to investigate the influence of the GNP in the electric response. The results obtained, show that the addition of GNP amounts up to 0.75 wt. % to the epoxy matrix improved the flexural results (Figure 1a). Concerning the electromechanical properties, it was possible to conclude that both laminate composites, with and without GNP, presented reproducible piezoresistive response, with a negative relative change in resistance (ΔR/R0) with increasing strain (), which may allow the health monitoring of the structure (Figure 1b).
- Graphene-based composite laminates for structural applicationsPublication . Parente, João Miguel Nunes; Reis, Paulo Nobre Balbis dos; Silva, Abílio Manuel Pereira da; Pereira, João Pedro NunesThis thesis explores the synthesis, microstructure and properties of polymer-matrix composites reinforced with graphene nanoplatelets (GNP), carbon nanotubes (CNT) and carbon nanofibers (CNF), both as individual fillers and in hybrid combinations. The aim is to develop structural materials with high mechanical performance and integrated self-sensing capabilities. Nanocomposites were produced by dispersing nanoparticles in epoxy resin, followed by thermal curing. Mechanical and sensing behaviour were evaluated using three-point bending and cyclic fatigue tests under realistic loading conditions. Viscosity measurements show that GNP or CNF can increase resin viscosity by up to 74 %, which challenges processing at higher loadings. Curing at 5 °C yields the best flexural strength and surface hardness, with GNP-reinforced composites showing up to 24.8 % strength improvement. Volumetric shrinkage during cure varies with filler type: GNP increases shrinkage by 91 %, while CNF reduces it by 77 %, underscoring the role of nanoparticle–matrix interactions. In fibre-reinforced laminates, placing glass fibres on the compression side of hybrid carbon/glass layups enhances both load and deflection at peak, with a 3G/5C configuration achieving a 5.9 % higher peak force and 13.1 % greater deflection than the reverse. Incorporating 0.75 wt. % GNP into carbon-fibre laminates raises bending stiffness and extends fatigue life by 15.1 %, while increases of 10.6 % and 9.2 % are observed in hybrid and glass-fibre laminates. These enhancements show that even low graphene concentrations effectively delay fatigue damage. Combining CNT and GNP at equal loadings (0.375 wt. % each) yields synergistic gains in stiffness and strength. In carbon-fibre composites, strength and stiffness rise by 11 % and 18 %, respectively; glass-fibre composites show gains of 8 % and 55 %. Electrical resistance monitoring during fatigue reveals gauge factors up to three times those of commercial strain gauges, with stress-amplitude sensitivity improving by 20.1 % in carbon composites and 32.4 % in glass composites. This confirms high-sensitivity and stable self-sensing. The integration of hybrid nanofillers with mechanical and electrical performance validation forms a framework for designing multifunctional composites. Key challenges remain in scaling uniform nanoparticle dispersion, ensuring long-term network stability and standardizing sensor calibration. Addressing these issues is essential for translating laboratory results into practical Structural Health Monitoring (SHM) applications.