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Projeto de investigação
Institute of Nanostructures, Nanomodelling and Nanofabrication
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Publicações
Healable Cellulose Iontronic Hydrogel Stickers for Sustainable Electronics on Paper
Publication . Cunha, Inês; Martins, Jorge; Gaspar, Diana; Bahubalindruni, Pydi Ganga; Fortunato, Elvira; Martins, Rodrigo; Pereira, Luís; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; Wiley
Novel nature-based engineered functional materials combined with sustainable and economically efficient processes are among the great challenges for the future of mankind. In this context, this work presents a new generation of versatile flexible and highly conformable regenerated cellulose hydrogel electrolytes with high ionic conductivity and self-healing ability, capable of being (re)used in electrical and electrochemical devices. They can be provided in the form of stickers and easily applied as gate dielectric onto flexible indium–gallium–zinc oxide transistors, decreasing the manufacturing complexity. Flexible and low-voltage (<2.5 V) circuits can be handwritten on-demand on paper transistors for patterning of conductive/resistive lines. This user-friendly and simplified manufacturing approach holds potential for fast production of low-cost, portable, disposable/recyclable, and low-power ion-controlled electronics on paper, making it attractive for application in sensors and concepts such as the “Internet-on-Things.”.
Development of Graphene Based Supercapacitors
Publication . Almeida, António Carranca de; Ferreira, Isabel
The modern world is gasping for electrical energy, from our homes to our daily used devices such as phones, computers and even to our cars. Everything needs to be connected to a battery and the solution existent is becoming obsolete. The market is with a huge gap and supercapacitors are the answer for that space. Graphene assumes a role play in this field for its amazing surface area and its conductivity, making it a perfect candidate for the electrodes of this devices. In this work, two synthesis of graphene were produce: laser reduction of graphene oxide and electrochemical exfoliation of graphite.
The first one allows to develop patterns and build the devices in graphene oxide film, producing 2D supercapacitors. The geometry and the influence of the electrolyte were studied to maximize the capacitance. The graphene produced were analysed for its conductivity, quality and uniformity by CV curves, SEM and Raman Spectroscopy.
The electrochemical exfoliation allows to start from graphite and use a salt solution with application of voltage, which is an economic and safer alternative for producing graphene. Several concentrations of Na2SO4 were tested and all the material produced by this technique was characterized with Raman Spectroscopy, SEM and TEM images to evaluate the procedure.
Sustainable carbon sources for green laser-induced graphene
Publication . Claro, Pedro I. C.; Pinheiro, Tomás; Silvestre, Sara L.; Marques, Ana C.; Coelho, João; Marconcini, José M.; Fortunato, Elvira; Luiz, Luiz H.; Martins, Rodrigo; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; AIP - American Institute of Physics
Since the discovery of laser-induced graphene (LIG), significant advances have been made to obtain green LIG (gLIG) from abundant, eco-friendly, natural, and organic renewable bio-based carbon sources. Recently, some sustainable and cost-effective electronic devices have been designed with gLIG, resulting in diverse solutions to the environmental impact caused by electronic waste (e-waste). However, there are still several challenges that must be addressed regarding the widespread market implementation of gLIG-based products, from synthesis to practical applications. In this review, we focus on sustainable precursor sources, their conversion mechanisms, physical and chemical properties and applications, along with the challenges related to its implementation, showing the future opportunities and perspectives related to this promising new material. Various systems based on gLIG for energy storage, electrocatalysis, water treatment, and sensors have been reported in the literature. Additionally, gLIG has been proposed for ink formulation or incorporation into polymer matrices, to further expand its use to non-carbon-based substrates or applications for which pristine LIG cannot be directly used. In this way, it is possible to apply gLIG on diverse substrates, aiming at emerging wearable and edible electronics. Thus, this review will bring an overview of gLIG developments, in accordance with the European Green Deal, the United Nations Sustainable Development Goals and the new era of internet-of-things, which demands cost-effective electronic components based on the principles of energy efficiency and sustainable production methods.
The early metallurgy in Southwestern Iberia: metals from the Chalcolithic Settlement of São Pedro (Redondo)
Publication . Vidigal, Rosa Orestes Cerdeira; Valério, Pedro; Araújo, Maria de Fátima; Silva, Rui
Archaeological excavations carried out in the archaeological site of São Pedro (Southern Portugal) revealed a Chalcolithic settlement occupied in different moments of the 3rd millennium BC. The material culture recovered includes different types of materials, such as ceramics, lithics and metals. The later comprises about 30 artefacts with different typologies such as tools (e.g. awls, chisels and a saw) and weapons (e.g. daggers and arrowheads) mostly belonging to the 2nd and 3rd quarter of the 3rd millennium BC.
In the present work the collection of chalcolithic metallic artefacts recovered in São
Pedro was characterized. Analytical studies involved micro energy dispersive X-ray fluorescence spectrometry (micro-EDXRF) to determine elemental composition, together with optical microscopy and Vickers microhardness testing for microstructural characterisation and hardness determination.
Main results show copper with variable amounts of arsenic and very low content of
other impurities, such as iron. Moreover, nearly half of the collection is composed by
arsenical copper alloys (As > 2 wt.%) and an association was found between arsenic content and typology since the weapons group (mostly daggers) present higher values than tools (mostly awls). These results suggest some criteria in the selection of arsenic-rich copper ores or smelting products. Furthermore, after casting an artefact would have been hammered, annealed and sometimes, finished with a hammering operation. Additionally, microstructural variations in this collection reveal somewhat different operational conditions during casting, annealing and forging, as expected in such a primitive metallurgy.
Moreover the operational sequence seems to be used to achieve the required shape to the object, rather than to intentionally make the alloy harder.
Overall, this study suggests that Chalcolithic metallurgists might have a poor control
of the addition of arsenic and/or were unable to use this element to increase the hardness of tools and weapons.
Finally, the compositions, manufacturing processes and hardness were compared to
those from neighbouring regions and different chronological periods.
Rail-to-Rail Timing Signals Generation Using InGaZnO TFTs for Flexible X-Ray Detector
Publication . Bahubalindruni, Pydi Ganga; Barquinha, Pedro; Tiwari, Bhawna; Pereira, Maria; Santa, Ana; Martins, Jorge; Rovisco, Ana; Tavares, Vitor; Martins, Rodrigo; Fortunato, Elvira; DCM - Departamento de Ciência dos Materiais; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); Institute of Electrical and Electronics Engineers (IEEE)
This paper reports on-chip rail-to-rail timing signals generation thin-film circuits for the first time. These circuits, based on a-IGZO thin-film transistors (TFTs) with a simple staggered bottom gate structure, allow row and column selection of a sensor matrix embedded in a flexible radiation sensing system. They include on-chip clock generator (ring oscillator), column selector (shift register) and row-selector (a frequency divider and a shift register). They are realised with rail-to-rail logic gates with level-shifting ability that can perform inversion and NAND logic operations. These logic gates are capable of providing full output swing between supply rails, $V_{DD}$ and $V_{SS}$ , by introducing a single additional switch for each input in bootstrapping logic gates. These circuits were characterised under normal ambient atmosphere and show an improved performance compared to the conventional logic gates with diode connected load and pseudo CMOS counterparts. By using these high-performance logic gates, a complete rail-to-rail frequency divider is presented from measurements using D-Flip Flop. In order to realize a complete compact system, an on-chip ring oscillator (output clock frequency around 1 kHz) and a shift register are also presented from simulations, where these circuits show a power consumption of 1.5 mW and 0.82 mW at a supply voltage of 8 V, respectively. While the circuit concepts described here were designed for an X-ray sensing system, they can be readily expanded to other domains where flexible on-chip timing signal generation is required, such as, smart packaging, biomedical wearable devices and RFIDs.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UID/CTM/50025/2013