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Projeto de investigação
Smart ZnO membrane applied to motion sensing
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Flexographic Printed Flexible Thermochromic Stickers for Smart Sensing Applications
Publication . Morais, M.; Figueira, J.; Corvo, M. C.; Peixoto, M.; Oliveira, Duarte Belo de; Gonçalves, A.; Fortunato, E.; Martins, R.; Carlos, E.; Pinto, J. V.; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); John Wiley and Sons Ltd
The growing demand for thermochromic materials in areas such as food packaging requires the development of fast-response and extended-life materials. The use of metal cation-ionic liquid complexes is increasing due to the easiness to tailor their properties, leading to changes in thermochromic response. This work presents the synthesis and introduction of thermochromic 1-butyl-3-methylimidazolium chloride and 4-chloronickelate ([BMIm]2[NiCl4]) complexes into water-based inks. Formulations with varying concentrations of complexes (10–40 wt.%) are printed on tags thorugh a roll-to-roll process and tested between 30–45 °C. Also, films with one to five layers are analyzed for color contrast and different encapsulating materials are studied to improve the thermochromic films' robustness. The optimal films, with three layers of ink with 40 wt.% complexes encapsulated with Fixomull Transparent present enhanced color contrast and fast response time. Red-green-blue analysis is performed on these films, revealing a blue/red ratio of 1.7 after heating at 40 °C for 30 min. This work paves the way for developing flexible stickers with fast response and high contrast. The innovative and straightforward thermochromic inks' production process and compatibility with large-scale manufacturing show their promising future as cost-effective stickers for smart packaging applications, such as visual indicators of ideal food consumption temperatures.
One-step production of laser-induced graphene via CO2 laser on agarose-lignin membranes
Publication . Machado, Beatriz S.; Morais, Maria; Pinheiro, Tomás; Deuermeier, Jonas; Teixeira, Vasco; Nunes, Daniela; Martins, Rodrigo; Inácio, José M.; Fortunato, Elvira; Almeida, Henrique V.; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; NOVA Medical School|Faculdade de Ciências Médicas (NMS|FCM); IOP Publishing
Laser-induced graphene (LIG) is a highly promising material for bioelectronics due to its excellent electrical conductivity, high surface area and biocompatibility. Nevertheless, the functionalization of biocompatible substrates with LIG is essential to propel the use of LIG-derived technologies forward in bioengineering. This study demonstrates the successful fabrication of LIG on agarose-lignin membranes using a single-step CO2 laser process. Membranes with 3 or 5 wt.% agarose, and 0.25 or 0.5 wt.% lignin were characterized for thickness and swelling degree to assess their behavior in a human-mimicking media. The LIG was comprehensively studied, measuring electrical and sheet resistance, and by employing techniques such as Raman spectroscopy, scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS) to evaluate graphitization efficiency and investigate its physicochemical characteristics. Electrical measurements revealed that the lowest sheet resistance achieved was equal to 139 ± 2 Ω sq−1, with lower laser speeds (below 76.2 mm s−1) and higher power settings (above 2.5 W) leading to improved conductivity. SEM analysis revealed a three-dimensional porous structure with pore sizes ranging from nanometers to micrometers, contributing to enhanced electrical conductivity and suitability for bioelectronic applications. EDS mapping further identified carbon, oxygen, and sodium. XPS analysis provided detailed insights into the chemical states of carbon, indicating high-quality graphene formation. The integration of LIG with these flexible, biocompatible membranes highlights their potential for use in bioelectronic devices, including wearable sensors and implantable medical technologies. These findings underscore the potential of agarose-lignin-based LIG as a scalable, eco-friendly platform for future bioelectronic innovations.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
OE
Número da atribuição
2022.13806.BD