The Impact of Including Carbonyl Iron Particles on the Melt Electrowriting Process

Melt electrowriting, a high-resolution additive manufacturing technique, is used in this study to process a magnetic polymer-based blend for the first time. Carbonyl iron (CI) particles homogenously distribute into poly(vinylidene fluoride) (PVDF) melts to result in well-defined, highly porous structures or scaffolds comprised of fibers ranging from 30 to 50 mu m in diameter. This study observes that CI particle incorporation is possible up to 30 wt% without nozzle clogging, albeit that the highest concentration results in heterogeneous fiber morphologies. In contrast, the direct writing of homogeneous PVDF fibers with up to 15 wt% CI is possible. The fibers can be readily displaced using magnets at concentrations of 1 wt% and above. Combined with good viability of L929 CC1 cells using Live/Dead imaging on scaffolds for all CI concentrations indicates that these formulations have potential for the usage in stimuli-responsive applications such as 4D printing.Peer reviewe

Piezoresponse, Mechanical, and Electrical Characteristics of Synthetic Spider Silk Nanofibers

This work presents electrospun nanofibers from synthetic spider silk protein, and their application as both a mechanical vibration and humidity sensor. Spider silk solution was synthesized from minor ampullate silk protein (MaSp) and then electrospun into nanofibers with a mean diameter of less than 100 nm. Then, mechanical vibrations were detected through piezoelectric characteristics analysis using a piezo force microscope and a dynamic mechanical analyzer with a voltage probe. The piezoelectric coefficient (d33) was determined to be 3.62 pC/N. During humidity sensing, both mechanical and electric resistance properties of spider silk nanofibers were evaluated at varying high-level humidity, beyond a relative humidity of 70%. The mechanical characterizations of the nanofibers show promising results, with Young’s modulus and maximum strain of up to 4.32 MPa and 40.90%, respectively. One more interesting feature is the electric resistivity of the spider silk nanofibers, which were observed to be decaying with humidity over time, showing a cyclic effect in both the absence and presence of humidity due to the cyclic shrinkage/expansion of the protein chains. The synthesized nanocomposite can be useful for further biomedical applications, such as nerve cell regrowth and drug delivery

Identification of Molecular Fluorophore as a Component of Carbon Dots able to Induce Gelation in a Fluorescent Multivalent-Metal-Ion-Free Alginate Hydrogel

We introduce a simple approach to fabricate fluorescent multivalent metal ion-free alginate hydrogels, which can be produced using carbon dots accessible from natural sources (citric acid and L-cysteine). Molecular fluorophore 5-oxo-2,3-dihydro-5H-[1,3]-thiazolo[3,2-a] pyridine-3,7-dicarboxylic acid (TPDCA), which is formed during the synthesis of carbon dots, is identified as a key segment for the crosslinking of hydrogels. The crosslinking happens through dynamic complexation of carboxylic acid groups of TPDCA and alginate cages along with sodium ions. The TPDCA derived hydrogels are investigated regarding to their thermal, rheological and optical properties, and found to exhibit characteristic fluorescence of this aggregated molecular fluorophore. Moreover, gradient hydrogels with tunable mechanical and optical properties and controlled release are obtained upon immersion of the hydrogel reactors in solutions of divalent metal ions (Ca2+, Cu2+, and Ni2+) with a higher affinity to alginate. - 2019, The Author(s).This contribution was made possible by the NPRP award [8–878–1–172] from Qatar National Research Fund (a member of Qatar foundation), Qatar University grant QUCG-CAM-19/20-2 and by a grant from the Germany/ Hong Kong Joint Research Scheme sponsored by the Research Grants Council of Hong Kong and the Germany Academic Exchange Service of Germany (Reference No.: G-CityU103/16). M.D. thanks the VEGA Scientific Grant Agency for support through project no. 2/0158/17.Scopu

Mussel-mimicking sulfobetaine-based copolymer with metal tunable gelation, self-healing and antibacterial capability

In the present study, the sulfobetaine-based copolymer bearing a dopamine functionality showed gel formation adjusted by the application of metal salts for gelation and various values of pH. Normally, the liquid-like solution of the sulfobetaine-based copolymer and metal cross-linkers is transformed to a gel-like state upon increasing the pH values in the presence of Fe3+ and Ti3+. Metal-induced coordination is reversible by means of the application of EDTA as a chelating agent. In the case of Ag+ ions, the gel is formed through a redox process accompanied with the oxidative coupling of the dopamine moieties and Ag0 particle formation. Mussel-mimicking and metal-dependent viscoelastic properties were observed for Fe3+, Ti3+, and Ag+ cross-linking agents, with additionally enhanced self-healing behavior in comparison with the covalently cross-linked IO4 ? analogues. Antibacterial properties can be achieved both in solution and on the surface using the proper concentration of Ag+ ions used for gelation; thus, a tunable amount of the Ag0 particles are formed in the hydrogel. The cytotoxicity was elucidated by the both MTT assay on the NIH/3T3 fibroblast cell line and direct contact method using human dermal fibroblast cell (F121) and shows the non-toxic character of the synthesized copolymer.P.K. gratefully acknowledge Qatar University internal grant QUUG-CAM-2017-1. This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic ? Program NPU I (LO1504). This work was also supported by the Maersk Oil R&TC Qatar project. This work was also made possible by NPRP grant # 9 ? 219-2-105 from the Qatar National Research Fund (A Member of The Qatar Foundation). The finding achieved herein is solely the responsibility of the authors.Scopu

Electrically conductive, transparent polymeric nanocomposites modified by 2D Ti3C2Tx (MXene)

The electrically conductive, transparent, and flexible self-standing thin nanocomposite films based on copolyamide matrix (coPA:Vestamelt X1010) modified with 2D Ti3C2Tx (MXene) nanosheets were prepared by casting and their electrical, mechanical and optical properties and then, were investigated. The percolation threshold of the MXene filler within the coPA matrix was found to be 0.05 vol. %, and the highest determined electrical conductivity was 1.4 × 10-2 S·cm-1 for the composite filled with 5 wt. % (1.8 vol. %) of MXene. The electrical conductivity of the asprepared MXene was 9.1 S·cm-1, and the electrical conductivity of the MAX phase (the precursor for MXene preparation) was 172 S·cm-1. The transparency of the prepared composite films exceeded 75%, even for samples containing 5 wt. % of MXene, as confirmed by UV spectroscopy. The dynamic mechanical analysis confirmed the improved mechanical properties, such as the storage modulus, which improved with the increasing MXene content. Moreover, all the composite films were very flexible and did not break under repeated twisting. The combination of the relatively high electrical conductivity of the composites filled with low filler content, an appropriate transparency, and good mechanical properties make these materials promising for applications in flexible electronics.Author Contributions: Conceptualization, I.K. and M.M.; methodology, I.K. and P.S.; software, P.S.; validation, P.S. A.T.; formal analysis, P.S., Z.S., M.M, and Ma.M.; investigation, A.T., P.S., M.M., Ma.M., J.P. and A.P.; resources, I.K.; data curation, P.S., J.P., I.K., Ma.M., and M.M.; writing—original draft preparation, A.T., P.S., M.M. and Z.S.; writing—review and editing, I.K., M.M. and P.S.; visualization, P.S., J.P. and A.P.; supervision, I.K.; project administration, I.K.; funding acquisition, I.K.; Funding: This publication was supported by Qatar University Collaborative High Impact Grant QUHI-CENG-18/19-1. The findings achieved herein are solely the responsibility of the authors

Energy harvesting technologies for structural health monitoring of airplane components - a review

With the aim of increasing the efficiency of maintenance and fuel usage in airplanes, structural health monitoring (SHM) of critical composite structures is increasingly expected and required. The optimized usage of this concept is subject of intensive work in the framework of the EU COST Action CA18203 "Optimising Design for Inspection" (ODIN). In this context, a thorough review of a broad range of energy harvesting (EH) technologies to be potentially used as power sources for the acoustic emission and guided wave propagation sensors of the considered SHM systems, as well as for the respective data elaboration and wireless communication modules, is provided in this work. EH devices based on the usage of kinetic energy, thermal gradients, solar radiation, airflow, and other viable energy sources, proposed so far in the literature, are thus described with a critical review of the respective specific power levels, of their potential placement on airplanes, as well as the consequently necessary power management architectures. The guidelines provided for the selection of the most appropriate EH and power management technologies create the preconditions to develop a new class of autonomous sensor nodes for the in-process, non-destructive SHM of airplane components.The work of S. Zelenika, P. Gljušcic, E. Kamenar and Ž. Vrcan is partly enabled by using the equipment funded via the EU European Regional Development Fund (ERDF) project no. RC.2.2.06-0001: “Research Infrastructure for Campus-based Laboratories at the University of Rijeka (RISK)” and partly supported by the University of Rijeka, Croatia, project uniri-tehnic-18-32 „Advanced mechatronics devices for smart technological solutions“. Z. Hadas, P. Tofel and O. Ševecek acknowledge the support provided via the Czech Science Foundation project GA19-17457S „Manufacturing and analysis of flexible piezoelectric layers for smart engineering”. J. Hlinka, F. Ksica and O. Rubes gratefully acknowledge the financial support provided by the ESIF, EU Operational Programme Research, Development and Education within the research project Center of Advanced Aerospace Technology (Reg. No.: CZ.02.1.01/0.0/0.0/16_019/0000826) at the Faculty of Mechanical Engineering, Brno University of Technology. V. Pakrashi would like to acknowledge UCD Energy Institute, Marine and Renewable Energy Ireland (MaREI) centre Ireland, Strengthening Infrastructure Risk Assessment in the Atlantic Area (SIRMA) Grant No. EAPA\826/2018, EU INTERREG Atlantic Area and Aquaculture Operations with Reliable Flexible Shielding Technologies for Prevention of Infestation in Offshore and Coastal Areas (FLEXAQUA), MarTera Era-Net cofund PBA/BIO/18/02 projects. The work of J.P.B. Silva is partially supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/FIS/04650/2020. M. Mrlik gratefully acknowledges the support of the Ministry of Education, Youth and Sports of the Czech Republic-DKRVO (RP/CPS/2020/003

The Influence of Incorporating Plastic within Concrete and the Potential Use of Microwave Curing; A Review

In recent decades, researchers have used plastic to replace natural aggregates (NAs), or as filler and fibre within the concrete. This particular paper puts forward a review that gives comprehensive consideration to the properties and drawbacks, of concrete that contains plastic. As such, it may be hypothesised that poor bond capacity and higher air content due to inclusion of plastic aggregate (PA) within concrete are the predominant factors that reduce the properties in terms of mechanics and durability. In that regard, this study has put forward a new method of curing using microwave irradiation for improvement with respect to those factors. So, that there can be further improvement with regard to overall durability with respect to advanced chemical and hydrophobic resistivity and enhanced performance for conventional concrete with respect to bonding and ductility

Dropout von Mädchen und Frauen aus dem vereinsorganisierten Fußballsport

In dieser Arbeit werden die potentiellen Beweggründe von Mädchen und Frauen aus dem vereinsorgansierten Fußballsport auszusteigen mittels einer quantitativen Forschungsmethode analysiert. Die Dropout-Ursachen werden über einen persönlich konstruierten Fragebogen anhand einer Stichprobe von 445 ehemaligen Vereinsspielerinnen im Fußballsport untersucht. Der Fragebogen überprüft die Zusammenhänge des Dropout- Verhaltens der Probandinnen und den möglichen Ausstiegsgründen – Vorbereitung auf die nachsportliche Karriere, Anstieg des Zeitaufwandes, Gesellschaftliche Wahrnehmung Fußball sei ein Männersport, Angebot an Sportalternativen, Auftreten von Sportverletzungen, Schwierigkeiten beim Übergang in den Erwachsenenbereich, Probleme mit dem Leistungspotential – die vom Autor der Studie angenommen wurden. Tendenzen bezüglich der Dropout-Ursache und dem Alter der Athletinnen zum Zeitpunkt des Ausstiegs werden in den Ergebnissen der Datenerhebung präsentiert. Demnach wird die Sichtweise der Beweggrunde die Karriere im Verein zu beenden über die Teilnehmerinnenstruktur vermittelt. Festzuhalten ist, dass keine vom Autor angenommene These hauptverantwortlich für den Dropout von Mädchen und Frauen aus dem vereinsorganisiertem Fußballsport ist, sondern die Vielzahl der Barrieren im Frauenfußball eine noch schnellere Entwicklung dieser Sportart verhindern. Neben der Forschung widmet sich die Arbeit dem Vorrücken von Frauen in Männerdomänen und den Schwierigkeiten, mit denen sie sich auseinander setzen müssen, dem Dropout im Frauenfußball und der Stellung der Sportart in Österreich.The following thesis will analyze with the means of quantitative research the potential motives of girls and women to leave soccer clubs. The drop-out rates will be examined via a survey comprising of a sample of 445 women who have previously played for a team. This survey will assess the causality of the dropout behavior and the possible dropout motives. The latter consist of the following choice made by the author of the survey: preparation for a career beyond club sport, increase of expenditure of time, societal perception of soccer as a traditionally male sport, range of various other types of sports, incidents of sport related injuries, difficulties in the transition to adulthood, and difficulties with performance potential. Tendencies in connection to the motives for a dropout and the age of the athletes at the time of the dropout will be presented in the findings of the data collection. It can be said that none of the motives chosen by the author was primarily responsible for the dropout of girls and women from soccer clubs. Instead a plurality of obstructions in women’s soccer prevents a faster development of this type of sport. Beside this study, this thesis also discusses the advancement of women in male dominated fields, the difficulties women have to deal with, the drop-out in women’s soccer and the social status of this type of sport in Austria