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Projeto de investigação
Institute of Nanostructures, Nanomodelling and Nanofabrication
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Design and development of open-source, multi-purpose wire arc additive manufacturing machine
Publication . Arthur, Nithin Joseph Reddy Sagili; Liu, Lei; Oliveira, João Pedro; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; Springer Science Business Media
Wire arc additive manufacturing (WAAM) is a promising technology offering capabilities of high deposition rate and low processing and equipment setup cost and the possibility to create components with moderate geometrical complexity. However, wide scale industrialization of this technology is constrained by its complex thermal signature which demands an interdisciplinary approach of integrating auxiliary technologies aiming at controlling and monitoring the process often requiring costly upgrades of ancillary systems. These challenges can be addressed by developing flexible and adaptable WAAM systems that incorporate open-source solutions for developing innovative and customized auxiliary add-ons mitigating proprietary barriers and scale-up expenditures. In this work, we present the design and construction of a scalable WAAM machine featuring three-axis rectilinear motion system with a working envelope suited for small- to medium-sized components. The system integrates a customized weld torch and multiple wire feeder utilizing widely available materials to ensure functionality and cost-effectiveness. An open-source 32-bit control board is employed to achieve coordinated operation of multiple systems. A detailed assessment and selection criteria of various motion control hardware is provided. Additionally, pioneering summary of control boards with significant potential for expansion into metal additive manufacturing is also presented. To validate the machine functionality, multi-layer deposition along X–Z and multi-bead deposition along X–Y axes were conducted. These results demonstrate the seamless synchronization of the motion control, welder, and wire feeder systems, achieving defect-free depositions. Conductive and radiative electromagnetic interference mitigation measures are detailed, providing a practical guidance to simplify the development of customizable WAAM machines.
Screen-printed, flexible, and eco-friendly thermoelectric touch sensors based on ethyl cellulose and graphite flakes inks
Publication . Figueira, J.; Bonito, R. M.; Carvalho, J. T.; Vieira, E. M. F.; Gaspar, C.; Loureiro, Joana; Correia, J. H.; Fortunato, E.; Martins, R.; Pereira, L.; DCM - Departamento de Ciência dos Materiais; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; IOP Publishing
Despite the undoubtable interest in energy conversion, thermoelectric (TE) materials can be approached from a temperature-sensitive perspective, as they can detect small thermal stimuli, such as a human touch or contact with cold/hot objects. This feature offers possibilities for different applications one of them being the integration with scalable and cost-effective, biocompatible, flexible, and lightweight thermal sensing solutions, exploring the combination of sustainable Seebeck coefficient-holding materials with printing techniques and flexible substrates. In this work, ethyl cellulose and graphite flakes inks were optimized to be used as functional material for flexible thermal touch sensors produced by screen-printing. Graphite concentrations of 10, 20 and 30 wt% were tested, with 1, 2 and 3 printed layers on four different substrates—office paper, sticker label paper, standard cotton, and organic cotton. The conjugation of these variables was assessed in terms of printability, sheet resistance and TE response. The best electrical-TE output combination is achieved by printing two layers of the ink with 20 wt% of graphite on an office paper substrate. Subsequently, thermal touch sensors with up to 48 TE elements were produced to increase the output voltage response (>4.5 mV) promoted by a gloved finger touch. Fast and repeatable touch recognition were obtained in optimized devices with a signal-to-noise ratio up to 340 and rise times bellow 0.5 s. The results evidence that the screen-printed graphite-based inks are highly suitable for flexible TE sensing applications.
Bioactive Glass Modified with Zirconium Incorporation for Dental Implant Applications
Publication . Hammami, Imen; Gavinho, Sílvia Rodrigues; Pádua, Ana Sofia; Sá-Nogueira, Isabel; Silva, Jorge Carvalho; Borges, João Paulo; Valente, Manuel Almeida; Graça, Manuel Pedro Fernandes; DF – Departamento de Física; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UCIBIO - Applied Molecular Biosciences Unit; DCV - Departamento de Ciências da Vida; DCM - Departamento de Ciência dos Materiais; MDPI - Multidisciplinary Digital Publishing Institute
Implantology is crucial for restoring aesthetics and masticatory function in oral rehabilitation. Despite its advantages, certain issues, such as bacterial infection, may still arise that hinder osseointegration and result in implant rejection. This work aims to address these challenges by developing a biomaterial for dental implant coating based on 45S5 Bioglass® modified by zirconium insertion. The structural characterization of the glasses, by XRD, showed that the introduction of zirconium in the Bioglass network at a concentration higher than 2 mol% promotes phase separation, with crystal phase formation. Impedance spectroscopy was used, in the frequency range of 102–106 Hz and the temperature range of 200–400 K, to investigate the electrical properties of these Bioglasses, due to their ability to store electrical charges and therefore enhance the osseointegration capacity. The electrical study showed that the presence of crystal phases, in the glass ceramic with 8 mol% of zirconium, led to a significant increase in conductivity. In terms of biological properties, the Bioglasses exhibited an antibacterial effect against Gram-positive and Gram-negative bacteria and did not show cytotoxicity for the Saos-2 cell line at extract concentrations up to 25 mg/mL. Furthermore, the results of the bioactivity test revealed that within 24 h, a CaP-rich layer began to form on the surface of all the samples. According to our results, the incorporation of 2 mol% of ZrO2 into the Bioglass significantly improves its potential as a coating material for dental implants, enhancing both its antibacterial and osteointegration properties.
Ionic Liquids as Extreme Pressure Additives for Bearing Steel Applications
Publication . Donato, Mariana T.; Nautiyal, Pranjal; Deuermeier, Jonas; Branco, Luís C.; Saramago, Benilde; Colaço, Rogério; Carpick, Robert W.; DQ - Departamento de Química; Faculdade de Ciências e Tecnologia (FCT); LAQV@REQUIMTE; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; DCM - Departamento de Ciência dos Materiais; Springer
The protection of steel surfaces from wear under extreme pressure conditions is of major importance in several industries as it provides better performance and longer life of machinery. The motivation for this work was to study the lubrication of steel by ionic liquids (ILs), which have recently emerged as greener alternatives to commercial lubricants and additives. Three ILs based on sulfur-containing anions, used as 2-wt% additives in polyethylene glycol base oil (MW 200; PEG 200), were tested in the lubrication of ASTM 52100 bearing steel contacts in extreme pressure conditions (under mixed lubrication with a Hertzian pressure of 1.12 GPa) using a mini traction machine (MTM). Due to the poor resistance to corrosion of bearing steel, a semi-ester of succinic acid derivative corrosion inhibitor (Lanxess RC 4801) was added to the mixtures at a 1 wt% concentration. The ILs 1-hexyl-methylimidazolium trifluoromethanesulfonate ([C6mim][TfO]) and 1-hexyl-4-picolinium trifluoromethanesulfonate ([C6-4-pic][TfO]) revealed promising results in terms of surface protection of bearing steel. In contrast, 4-picolinium hydrogen sulfate ([4-picH][HSO4]) as 2-wt% additive to PEG 200 + 1% RC 4801 did not show any improvement in wear performance compared to neat PEG 200 + 1% RC 4801. PEG 200 + 2% [C6mim][TfO] + 1%RC 4801 allowed for a decrease in wear up to ~ 76% and PEG 200 + 2% [C6-4-pic][TfO] + 1%RC 4801 up to ~ 46% when compared with neat PEG 200 + 1% RC 4801. Optical microscopy images suggest the formation of an adsorbed layer, which was further supported by chemical analysis via x-ray photoelectron spectroscopy (XPS) data for [C6mim][TfO]. Graphical abstract: (Figure presented.)
Sustainable Multi-stack Printed Heaters on Paper with Efficient Heat Distribution
Publication . Papanastasiou, Dorina T.; Morais, Daniel; Martins, Raquel Azevedo; Fortunato, Elvira; Martins, Rodrigo; Barquinha, Pedro; Carlos, Emanuel; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; ACS - American Chemical Society
Printed heaters are emerging as a promising solution for flexible, sustainable, and eco-friendly applications, with potential uses ranging from wearable and portable devices to the automotive industry. This study addresses key challenges in heat uniformity and mechanical protection, by employing screen printing with water-based inks and biodegradable paper substrates. The multi-stack heater, composed of carbon, silver, and aluminum oxide (C/Ag/AlOx), demonstrates excellent electrical and thermal performance. At 5 V, the C/Ag/AlOx heater achieves a peak temperature of approximately 120 °C, with spatial temperature fluctuations within ±3 °C, offering superior thermal uniformity compared to bare Ag and Ag/AlOx heaters, which exhibit temperature gradients up to 10 °C. All configurations show robust durability during 6 h of 5 V cycling and minimal resistance changes during environmental stability tests under 80 °C and 80% relative humidity. In tape adhesion tests, the C/Ag/AlOx heater maintained nearly unchanged resistance after several peel cycles thanks to the protective AlOx coating. Finally, the ultralow cost multi-stack configuration (0.20 € per heater) embedded in a skin bandage reached a maximum temperature of 50 °C at 3.5 V, with a power density of 0.08 W/cm2, highlighting its potential for precise temperature control and homogeneous heating in thermotherapy applications.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UIDP/50025/2020