Centre for Rapid and Sustainable Product Development

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Advanced face mask filters based on PCL electrospun meshes dopped with antimicrobial MgO and CuO nanoparticles

Publication . Ferreira, Carolina A. M.; Guerreiro, Sara F.C.; Valente, Joana F. A.; Patrício, Tatiana M.F.; Alves, Nuno; Mateus, Artur; Dias, Juliana R.

The pandemic situation caused by coronavirus clearly demonstrated the need for alternatives able to protect the respiratory tract and inactivate the infectious agents. Based on this, antibacterial face-mask filters of polycaprolactone (PCL) dopped with magnesium oxide (MgO) and copper oxide (CuO) nanoparticles (NPs) were produced using an electrospinning technique. A morphological analysis of electrospun meshes evaluated the success of nanoparticles’ incorporation as well as the average fibers’ diameters (481 +- 272 nm). The performance of electrospun nanofibers was also assessed in terms of tensile strength (0.88 +- 0.25 MPa), water vapor permeability (11,178.66 +- 35.78 g.m-2.day-1), stability under wet conditions and antibacterial activity according to the standard guidelines. The filters showed structural stability up to 2 h of washing and improved antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) for optimized concentrations of MgO and CuO NPs. Overall, electrospun meshes with antibacterial activity were successfully developed for advanced filtering applications.

2022Journal article

Open access

Optimization of extraction conditions for Gracilaria gracilis extracts and their antioxidative stability as mart of microfiber food coating additives

Publication . Reboleira, João; Ganhão, Rui; Mendes, Susana; Adão, Pedro; Andrade, Mariana; Vilarinho, Fernanda; Sanches-Silva, Ana; Sousa, Dora; Mateus, Artur; Bernardino, Susana

Incorporation of antioxidant agents in edible films and packages often relies in the usage of essential oils and other concentrated hydrophobic liquids, with reliable increases in antimicrobial and antioxidant activities of the overall composite, but with less desirable synthetic sources and extraction methods. Hydroethanolic extracts of commercially-available red macroalgae Gracilaria gracilis were evaluated for their antioxidant potential and phenolic content, as part of the selection of algal biomass for the enrichment of thermoplastic film coatings. The extracts were obtained through use of solid-liquid extractions, over which yield, DPPH radical reduction capacity, total phenolic content, and FRAP activity assays were measured. Solid-to-liquid ratio, extraction time, and ethanol percentages were selected as independent variables, and response surface methodology (RSM) was then used to estimate the e ect of each extraction condition on the tested bioactivities. These extracts were electrospun into polypropylene films and the antioxidant activity of these coatings was measured. Similar bioactivities were measured for both 100% ethanolic and aqueous extracts, revealing high viability in the application of both for antioxidant coating purposes, though activity losses as a result of the electrospinning process were above 60% in all cases.

2020Journal article

Open access

The study of new NiTi actuators to reinforce the wing movement of aircraft systems

Publication . Braga, Rafael; Rodrigues, Patrícia Freitas; Cordeiro, Hélder; Carreira, Pedro; Vieira, Maria Teresa

Actuators using Shape Memory Alloy (SMA) springs could operate in different mechanical systems requiring geometric flexibility and high performance. The aim of the present study is to highlight the potential of these actuators, using their dimensional variations resulting from the phase transformations of NiTi springs (SMA) to make the movements of the system’s mobile components reversible. This reversibility is due to thermal-induced martensitic transformation of NiTi springs. The transformation promotes the extended and retracted of the springs as the phase changing (martensite–austenite) creates movement in part of the system. Therefore, the phase transition temperatures of NiTi, evaluated by differential scanning calorimetry (DSC), are required to control the dimensional variation of the spring. The influence of the number of springs in the system, as well as how impacts on the reaction time were evaluated. The different numbers of springs (two, four, and six) and the interspaces between them made it possible to control the time and the final angle attained in the mobile part of the system. Mechanical resistance, maximum angle, and the system’s reaction time using different NiTi springs highlight the role of the actuators. Fused Deposition Modelling (FDM)/Material Extrusion (MEX) or Selective Laser Sintering (SLS) was selected for shaping the composite matrix system. A new prototype was designed and developed to conduct tests that established the relationship between the recoverable deformation of the matrix suitable for the application as well as the number and distribution of the actuators.

2022Journal article

Open access

3D-printed teeth in endodontics: Why, how, problems and future: A narrative review

Publication . Reis, Tiago; Barbosa, Cláudia; Franco, Margarida; Baptista, Catarina; Alves, Nuno; Castelo-Baz, Pablo; Martín-Cruces, José; Martin-Biedma, Benjamin

Three-dimensional printing offers possibilities for the development of new models in endodontics. Numerous studies have used 3D-printed teeth; however, protocols for the standardization of studies still need to be developed. Another problem with 3D-printed teeth is the different areas of literature requested to understand the processes. This review aims to gather evidence about 3Dprinted teeth on the following aspects: (1) why they are advantageous; (2) how they are manufactured; (3) problems they present; and (4) future research topics. Natural teeth are still the standard practice in ex vivo studies and pre-clinical courses, but they have several drawbacks. Printed teeth may overcome all limitations of natural teeth. Printing technology relies on 3D data and post-processing tools to form a 3D model, ultimately generating a prototype using 3D printers. The major concerns with 3D-printed teeth are the resin hardness and printing accuracy of the canal anatomy. Guidance is presented for future studies to solve the problems of 3D-printed teeth and develop well-established protocols, for the standardization of methods to be achieved. In the future, 3D-printed teeth have the possibility to become the gold standard in ex vivo studies and endodontic training.

2022Journal article

Open access

How to correctly estimate the electric field in capacitively coupled systems for tissue engineering: a comparative study

Publication . Meneses, João; Fernandes, Sofia; Alves, Nuno; Pascoal-Faria, Paula; Miranda, Pedro Cavaleiro

Capacitively Coupled (CCoupled) electric fields are used to stimulate cell cultures in Tissue Engineering. Knowing the electric field (E-Field) magnitude in the culture medium is fundamental to establish a relationship between stimulus strength and cellular effects. We analysed eight CCoupled studies and sought to corroborate the reported estimates of the E-Field in the culture medium. First, we reviewed the basic physics underlying CCoupled stimulation and delineated three approaches to estimate the E-field. Using these approaches, we found that the reported values were overestimated in five studies, four of which were based on incorrect assumptions. In all studies, insufficient information was provided to reproduce the setup exactly. Creating electrical models of the experimental setup should improve the accuracy of the E-field estimates and enhance reproducibility. For this purpose, we developed a free open-source tool, the E-field Calculator for CCoupled systems, which is available for download from an internet hosting platform.

2022Journal article

Open access