Hydrothermal ageing behavior of bioinspired material with piezoelectric functions for implant applications

Implant-bone fixation loss can occur 10-15 years after surgery. This is related to bone resorption and consecutive biofilm formation in the generated gap, which could lead to tissues inflammation and implant loss [1]. Current solutions are focused on primary osseointegration for implant early survival rate. In long term, they lose effectiveness due to implant foreign body reaction once bone metabolism is challenged by a non-part of the body. Bone is composed of piezoelectric materials with production of biological electricity due to collagen deformation and displacement of the local electric field [2]. Barium titanate is a lead-free piezoelectric bioceramic without toxicological risk and absence of foreign body reactions that can mimic natural bone piezoelectricity and inhibit bacterial adhesion [3]. The focus of this work is design, produce, and characterize a smart, bio-inspired, and multi-functional composite material to improve implant long-term bone regeneration and antibacterial effect. In this sense, a composite with BaTiO3 particles and bioinert ZrO2 was produced. 5%BaTiO3-ZrO2 composites were mixed in isopropanol alcohol and ultrasonicated for total dispersion, followed by press (200MPa) and sintering technic (1300-1500ºC). The different samples were characterized with SEM (Fig1.(a)), that present two distinct phases, XRD analysis, and subjected to hydrothermal ageing (Fig1.(b)), to evaluate the stability of the tetragonal zirconia phase. After 5h of accelerated ageing (≈10 years), monoclinic phase is more evident with the sintering temperature increment, but always lower than 25%, staying in according with ISO 13356:200, promising to be promising a potential replacement material for implant applications.This work was supported by FCT national funds under the national support to R&D units grant, through the reference project UIDB/04436/2020, UIDP/04436/2020, FunImp POCI-01-0145-FEDER-030498 and through the grant 2021.09001.BD

Multi‑mechanical waves against Alzheimer’s disease pathology: a systematic review

Alzheimer’s disease (AD) is the most common cause of dementia, affecting approximately 40 million people worldwide. The ineffectiveness of the available pharmacological treatments against AD has fostered researchers to focus on alternative strategies to overcome this challenge. Mechanical vibrations delivered in different stimulation modes have been associated with marked improvements in cognitive and physical performance in both demented and nondemented elderly. Some of the mechanical-based stimulation modalities in efforts are earlier whole-body vibration, transcranial ultrasound stimulation with microbubble injection, and more recently, auditory stimulation. However, there is a huge variety of treatment specifications, and in many cases, conflicting results are reported. In this review, a search on Scopus, PubMed, and Web of Science databases was performed, resulting in 37 papers . These studies suggest that mechanical vibrations delivered through different stimulation modes are effective in attenuating many parameters of AD pathology including functional connectivity and neuronal circuit integrity deficits in the brains of AD patients, as well as in subjects with cognitive decline and non-demented older adults. Despite the evolving preclinical and clinical evidence on these therapeutic modalities, their translation into clinical practice is not consolidated yet. Thus, this comprehensive and critical systematic review aims to address the most important gaps in the reviewed protocols and propose optimal regimens for future clinical application.FCT (Fundação para a Ciência e Tecnologia) through the grant with reference SFRH/BD/09375/2020, and in the scope of the projects UIDB/04436/2020, UIDP/04436/2020, and NORTE-01- 0145-FEDER-000023, funded by the European Fund for Regional Development (FEDER) of the Operational Programme for Competitiveness and Internationalization (POCI), by Portugal 2020

Comparative study of the tarnishing resistance of several coloured base gold alloys

The stability of coloured gold alloys may be dependent on the environment that involves them. This paper is concerned with the effect of an artificial sweat solution in the stability of several gold base alloys with different colours. The changes in the samples physical properties, colour, brightness, and reflectance were measured for several periods of immersion. Two types of alloys (purple and blue coloured alloys) showed to be sensitive to the artificial sweat solution. The other tested alloys have a high resistance to tarnishing comparable with the results obtained for pure gold

Inconel 718–Copper bimetallic joints fabricated by 3D multi-material laser powder bed fusion for aerospace components

Usually, aerospace components are subjected to high demanding operating conditions in terms of mechanical and thermal stresses. The structural integrity of these components is assured by the use of high strength and temperature-resistant materials such as Inconel alloys. However, these alloys are known to have low thermal conductivity, which makes it difficult to extract heat from inside the component. Copper-based alloys are widely used in the aerospace field due to their high thermal conductivity, high strength, good ductility and corrosion resistance. A 3D multi-material Inconel 718 – Copper solution was produced by laser powder bed fusion to be applied on a rocket engine wall aiming to improve its heat extraction ability. This approach combines high strength Inconel 718 and high thermal conductivity Copper in a single part, produced at once. The individual Inconel 718 and Copper zones and interface transition zone features were assessed in terms of metallurgical bonding and mechanical behaviour. This 3D multi-material Inconel 718 – Copper solution seems to be a promising approach since the two materials have a well-defined interface with no substantial defects. Inconel 718 and Copper seems to be capable to maintain its most important individual properties, high strength and high thermal conductivity

How does the Alzheimer’s disease brain respond to optomechanical stimuli?: a narrative review

This abstract will be presented as a poster at the 4th International Brain Stimulation Conference, in December 2021, in Charleston, USA.Alzheimer's disease (AD) is a neurodegenerative condition with enormous social and economic impact at a global scale. Given the inefficacy of the pharmacological treatments developed so far in decelerating/blocking AD pathology, the study and development of so-called alternative (i.e., non-pharmacological) and non-invasive therapies has become one of the major focuses of biomedical research on AD in recent years. Indeed, several researchers have demonstrated the therapeutic potential of optical and mechanical (i.e., optomechanical) stimuli in brain lesions. Among them, photobiomodulation (PBM, the application of modulated red/NIR light for therapeutic purposes) and tailored ultrasonic waves applied to the brain through transcranial ultrasound stimulation (TUSS) are at the forefront of clinical interventions with the potential to improve associated neuropathology and symptomatology of AD (e.g., reduction of protein aggregates deposition in the brain, increased functional connectivity and synchronization of neuronal activity, cognitive improvements), both at the preclinical and clinical levels. However, the biologic mechanisms differentially activated/stimulated during optomechanical stimulation are far from being understood. There are no proven data about the bioavailability of the stimulus energy and their bioeffects on signaling pathways, inflammation and clearance mechanisms, as well as on how these alterations relate with the behavioral improvement observed. Thus, this review compiles and describes possible biological mechanisms and alterations through which optomechanical stimuli can be effective in mitigating AD neuropathology and clinical symptoms. The topics reviewed here will be crucial for further development in the field of alternative, noninvasive brain stimulation approaches against AD, also contributing to all therapeutic interventions by transcranial stimulation in the future, enabling the development of customized therapies

Yttria/ceria stabilized zirconia composites: evaluation of microstructural, mechanical and color properties for biomedical applications

[Excerpt] 3-mol% Yttria-Stabilized Tetragonal Zirconia Polycrystal (3Y-TZP), a ceramic biomaterial, has been widely used in the dentistry field due to its biocompatibility, tooth-like color and mechanical properties [1]. Despite these advantages, its physical and mechanical properties tend to degrade as a result of a low-temperature aging process induced by its sensitivity to low-temperature degradation (LTD) when it is in contact with water that is already at human body temperature [2]. Because of this, many studies have been performed aiming at avoiding this phenomenon by replacing 3Y-TZP by 12 mol% ceria stabilized tetragonal zirconia polycrystal (12Ce-TZP). Nevertheless, compared to 3Y-TZP, 12Ce-TZP has lower strength which is partly related to its larger grain size [3]. [...]This work was supported by FCT national funds, under the national support to R&D units grant, through the reference project UIDB/04436/2020 and UIDP/04436/2020. Additionally, this work was also supported by FCT through the grant SFRH/BD/146324/2019

A novel approach for micro-antenna fabrication on ZrO2 substrate assisted by laser printing for smart implants

The use of Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) in medicine has rapidly expanded over the past decade, driven by its advantageous properties, showing potential to overcome titanium alloy in implant fabrication. The release of metal ions and the aesthetic problems of titanium alloy implants are the main reasons for this trend. In addition to meeting expectations regarding its properties, an implant must possess intrinsic capacities such as auto-diagnostic and auto-treatment. Thus, based on the concept of smart implants, this work proposes a hybrid approach for printing a part of the communication system of a zirconia implant by resorting to laser technology, aiming to endow the implant with intrinsic capacities. Therefore, the antenna was designed and then printed on the zirconia surface. The laser was applied as a versatile tool, whether for preparing the surface of the material in a subtractive way, by creating the micro-cavity, or for printing the silver-based antenna in an additive way through laser technology. The silver powder was used as the conductor material of the antenna. The results revealed that the antenna is capable of communicating from inside the body with the outside world without needing to have an exterior antenna attached to the skin.This work has been supported by the FCT (Fundação para a Ciência e Tecnologia -Portugal) in the scope of the projects UID/EEA/04436/2019; Magsense_POCI-01-0247-FEDER-033783, Add.Additive_Manufacturing to Portuguese Industry_POCI-01-0247-FEDER-024533, grant SFRH/BD/ 116554/2016 and the CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) for the grant 205791/2014-

A Scoping review on the polymerization of resin-matrix cements used in restorative dentistry

In dentistry, clinicians mainly use dual-cured or light-cured resin-matrix cements to achieve a proper polymerization of the organic matrix leading to enhanced physical properties of the cement. However, several parameters can affect the polymerization of resin-matrix cements. The main aim of the present study was to perform a scoping review on the degree of conversion (DC) of the organic matrix, the polymerization, and the light transmittance of different resin-matrix cements used in dentistry. A search was performed on PubMed using a combination of the following key terms: degree of conversion, resin cements, light transmittance, polymerization, light curing, and thickness. Articles in the English language published up to November 2022 were selected. The selected studies’ results demonstrated that restorative structures with a thickness higher than 1.5 mm decrease the light irradiance towards the resin-matrix cement. A decrease in light transmission provides a low energy absorption through the resin cement leading to a low DC percentage. On the other hand, the highest DC percentages, ranging between 55 and 75%, have been reported for dual-cured resin-matrix cements, although the polymerization mode and exposure time also influence the DC of monomers. Thus, the polymerization of resin-matrix cements can be optimized taking into account different parameters of light-curing, such as adequate light distance, irradiance, exposure time, equipment, and wavelength. Then, optimum physical properties are achieved that provide a long-term clinical performance of the cemented restorative materials

Production and optimization of 316L stainless steel dimples by laser surface texturing using Nd: YAG laser

Surface patterning is of increasing interest in modern manufacturing processes to achieve better results in terms of wear resistance and friction of mechanical parts and tools and, consequently, to improve their lifetime in service conditions [1]. Several approaches have been used to modify the surface properties of steel components, namely deposition of coatings, sandblasting, and texturing by electron beam, electric arc, or laser ablation [1,2]. In this work, laser technology was explored to produce dimples on the surface of 316L stainless steel samples. The production of textures can have several purposes, namely in tribological applications where they can reduce wear by acting as a reservoir for the lubricant or be reinforced with other materials (e.g. ceramics or intermetallic compounds), capable of improving the surface properties [1–3]. This work presents a detailed study on the texturing of a 316L stainless steel (dimples - circle design) by an Nd: YAG laser and its surface characterization by Scanning Electron Microscopy and analysis software (Image J) for obtaining their width (diameter) and depth. The texturing parameters are discussed herein. Results show that the width of the dimples is little influenced by the scan speed and wobble, but strongly affected by the combination of laser power and number of passes. On the other hand, wobble strongly influenced the depth of the dimples.This work was supported by FCT (Fundação para a Ciência e a Tecnologia) national funds, under the national support to R&D units grant, through the grant SFRH/BD/147460/2019, the project UIDB/04436/2020 and UIDP/04436/2020 and, also by project UIDB/00285/2020

Assessment of an exhaust thermoelectric generator incorporating thermal control applied to a heavy duty vehicle

The road transport industry faces the need to develop its fleet for lower energy consumption, pollutants and CO2 emissions. Waste heat recovery systems with Thermoelectric Generators (TEGs) can directly convert the exhaust heat into electric energy, aiding the electrical needs of the vehicle, thus reducing its dependency on fuel energy. The present work assesses the optimisation and evaluation of a temperature-controlled thermoelectric generator (TCTG) concept to be used in a commercial heavy-duty vehicle (HDV). The system consists of a heat exchanger with wavy fins (WFs) embedded in an aluminium matrix along with vapour chambers (VCs), machined directly into the matrix, that grant the thermal control based on the spreading of local excess heat by phase change, as proposed by the authors in previous publications and patents. The TCTG concept behaviour was analysed under realistic driving conditions. An HDV with a 16 L Diesel engine was simulated in AVL Cruise to obtain the exhaust gas temperature and mass flow rate for each point of two cycle runs. A model proposed in previous publications was adapted to the new fin geometry and vapour chamber configuration and used the AVL Cruise data as input. It was possible to predict the thermal and thermoelectric performance of the TCTG along the corresponding driving cycles. The developed system proved to have a good capacity for applications with highly variable thermal loads since it was able to uncouple the maximisation of heat absorption from the regulation of the thermal level at the hot face of the TEG modules, avoiding both thermal dilution and overheating. This was achieved by the controlled phase change temperature of the heat spreader, that would ensure the spreading of the excess heat from overheated to underheated areas of the generator instead of wasting excess heat. A maximum average electrical production of 2.4 kW was predicted, which resulted in fuel savings of about 2% and CO2 emissions reduction of around 37 g/km.This article was partially supported by projects COOLSPOT PTDC/EME-TED/7801/2020, UIDB/00481/2020 and UIDP/00481/2020 (Centre for Mechanical Technology and Automation—TEMA) and UIDB/04077/2020 (MEchanical Engineering and Resource Sustainability Center—MEtRICs)— Fundação para a Ciência e a Tecnologia (FCT); CENTRO-01-0145-FEDER-022083 (Centro2020), Norte2020, Compete2020, under the PORTUGAL 2020 Partnership Agreement, through Portuguese national funds of FCT/MCTES (PIDDAC) and the European Regional Development Fund