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Projeto de investigação
Integration of flexible and low-cost printed metal oxide memristors
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Cellulose-based encapsulation for all-printed flexible thermoelectric touch detectors
Publication . Figueira, Joana; Peixoto, Mariana; Gaspar, Cristina; Loureiro, Joana; Martins, Rodrigo; Carlos, Emanuel; Pereira, Luís; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; DCM - Departamento de Ciência dos Materiais; Springer
Printed and flexible electronics have gained considerable scientific attention in recent years, driving the demand for low-energy production techniques, eco-friendly materials and flexible substrates. However, effective encapsulation is essential to protect these devices in harsh environmental conditions. Thus, sustainable encapsulant materials are critical for advancing flexible electronics. In this work, we studied three encapsulant materials—commercial plastic, polyvinyl alcohol and ethyl cellulose—applied to thermoelectric touch sensors printed on paper and fabric substrates. Ethyl cellulose demonstrated promising properties in terms of flexibility, water resistance and transparency, along with a low carbon footprint. Encapsulated substrates with ethyl cellulose exhibited high contact angles (121° on fabric and 116° on paper), indicating robust water repellency. Thermal stability tests showed minimal mass loss (10%) at 315 °C, confirming its temperature resilience. Furthermore, sensors encapsulated with ethyl cellulose retained their electric performance after water submersion for 1 min and withstood 100 bending cycles, maintaining response times below 1 s and signal output around 100 µV. These findings highlight ethyl cellulose as a viable green encapsulant material compatible with large-scale sustainable electronics manufacturing.
Printed Zinc Tin Oxide Memristors for Reservoir Computing
Publication . Azevedo Martins, Raquel; Silva, Carlos; Deuermeier, Jonas; Milano, Gianluca; Rosero-Realpe, Mateo; Parreira, Carolina; Fortunato, Elvira; Martins, Rodrigo; Kiazadeh, Asal; Carlos, Emanuel; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); John Wiley and Sons Inc.
In this work, fully patterned zinc tin oxide (ZTO) memristors are introduced using inkjet printing. By targeting a scalable, solution-based fabrication approach, highly stable devices with excellent reproducibility and minimal variability are achieved, using ZTO as the active layer, silver (Ag) as the top electrode, and molybdenum as the bottom electrode. The use of sustainable materials like ZTO enhances scalability and environmental compatibility, paving the way for next-generation, low-power neuromorphic computing. The devices successfully fulfill the fundamental criteria for in materia implementation of physical reservoir computing (PRC), including nonlinearity and fading memory property. The devices are successfully trained for classification tasks with MNIST handwritten dataset, achieving 89.4% accuracy and 86.5% by processing 4-bit and 5-bit input temporal sequences. The integration of printed memristors into hardware-based PRC architecture simplifies training complexity, making them particularly advantageous for energy-efficient, wearable AI systems.
Microwave Synthesis of Visible-Light-Activated g-C3N4/TiO2 Photocatalysts
Publication . Matias, Maria Leonor; Reis-Machado, Ana S.; Rodrigues, Joana; Calmeiro, Tomás; Deuermeier, Jonas; Pimentel, Ana; Fortunato, Elvira; Martins, Rodrigo; Nunes, Daniela; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI AG
The preparation of visible-light-driven photocatalysts has become highly appealing for environmental remediation through simple, fast and green chemical methods. The current study reports the synthesis and characterization of graphitic carbon nitride/titanium dioxide (g-C3N4/TiO2) heterostructures through a fast (1 h) and simple microwave-assisted approach. Different g-C3N4 amounts mixed with TiO2 (15, 30 and 45 wt. %) were investigated for the photocatalytic degradation of a recalcitrant azo dye (methyl orange (MO)) under solar simulating light. X-ray diffraction (XRD) revealed the anatase TiO2 phase for the pure material and all heterostructures produced. Scanning electron microscopy (SEM) showed that by increasing the amount of g-C3N4 in the synthesis, large TiO2 aggregates composed of irregularly shaped particles were disintegrated and resulted in smaller ones, composing a film that covered the g-C3N4 nanosheets. Scanning transmission electron microscopy (STEM) analyses confirmed the existence of an effective interface between a g-C3N4 nanosheet and a TiO2 nanocrystal. X-ray photoelectron spectroscopy (XPS) evidenced no chemical alterations to both g-C3N4 and TiO2 at the heterostructure. The visible-light absorption shift was indicated by the red shift in the absorption onset through the ultraviolet-visible (UV-VIS) absorption spectra. The 30 wt. % of g-C3N4/TiO2 heterostructure showed the best photocatalytic performance, with a MO dye degradation of 85% in 4 h, corresponding to an enhanced efficiency of almost 2 and 10 times greater than that of pure TiO2 and g-C3N4 nanosheets, respectively. Superoxide radical species were found to be the most active radical species in the MO photodegradation process. The creation of a type-II heterostructure is highly suggested due to the negligible participation of hydroxyl radical species in the photodegradation process. The superior photocatalytic activity was attributed to the synergy of g-C3N4 and TiO2 materials.
Printed Memristors
Publication . Franco, Miguel; Kiazadeh, Asal; Martins, Rodrigo; Lanceros-Méndez, Senentxu; Carlos, Emanuel; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; Wiley
Industry 4.0 is accelerating the growth of connected devices, resulting in an exponential increase in generated data. The current semiconductor technology is facing challenges in miniaturization and power consumption, demanding for more efficient computation where new materials and devices need to be implemented. One of the most promising candidates for the next technological leap is the memristor. Due to their up-scale manufacturing, the majority of memristors employed conventional deposition techniques (physical and chemical vapor deposition), which can be highly costly. Recently, printed memristors have gained a lot of attention because of their potential for large-scale, fast, and affordable manufacturing. They can also help to reduce material waste, which supports the transition to a more sustainable and environmentally friendly economy. This review provides a perspective on the potential of printed electronics in the fabrication of memristive devices, presenting an overview of the main printing techniques, most suitable for memristors development. Additionally, it focuses on the materials used for the switching layer by comparing its performance. Ultimately, the application of printed memristors is highlighted by showing the tremendous evolution in this field, as well as the main challenges and opportunities that printed memristors are expected to face in the following years.
Low-Temperature Solution-Based Molybdenum Oxide Memristors
Publication . Martins, RA; Carlos, E; Kiazadeh, A; Martins, RA; Deuermeier, J; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; ACS - American Chemical Society
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
CEEC IND4ed
Número da atribuição
2021.03825.CEECIND/CP1657/CT0015