Environmentally friendly carrageenan-based ionic-liquid driven soft actuators

UID/FIS/04650/2020 UID/QUI/0686/2020 LA/P/0008/2020 PID2019-106099RB-C43/AEI/10.13039/501100011033A naturally derived polymer based on iota carrageenan and different ammonium and imidazolium based ionic liquids (ILs) are used for the development of environmentally friendly soft actuators. The influence of IL content and type and solvent evaporation temperature on the morphological and physico-chemical properties of the materials was evaluated, together with the effect on actuator functional response. Independently of the IL content and type, and the solvent evaporation temperature, a non-porous structure is obtained. The incorporation of the IL within the polymer matrix does not affect the thermal stability but leads to a decrease in the Young modulus for the different IL/carrageenan samples. The highest influence was observed by using the [Ch][DHP] IL at a filler content of 40% w/w with a decrease in the Young modulus from 748 MPa for the neat polymer to 145 MPa for the [Ch][DHP]/carrageenan sample. Furthermore, the ionic conductivity of the samples increases with increasing IL content, with the highest values being 2.9 × 10-6 S cm-1 and 1.2 × 10-6 S cm-1 for the samples with 40% w/w of [Bmim][FeCl4] and [Ch][DHP], respectively. Regarding the soft actuator performance, the maximum displacement was obtained for the [Ch][DHP]/carrageenan sample with an IL content of 40% w/w, showing a maximum displacement of 5.8 mm at a DC applied voltage of 9 V.publishersversionpublishe

Indirect X-ray detectors based on inkjet-printed photodetectors with a screen-printed scintillator layer

Organic photodetectors (PDs) based on printing technologies will allow to expand the current field of PD applications toward large-area and flexible applications in areas such as medical imaging, security, and quality control, among others. Inkjet printing is a powerful digital tool for the deposition of smart and functional materials on various substrates, allowing the development of electronic devices such as PDs on various substrates. In this work, inkjet-printed PD arrays, based on the organic thin-film transistor architecture, have been developed and applied for the indirect detection of X-ray radiation using a scintillator ink as an X-ray absorber. The >90% increase of the photocurrent of the PDs under X-ray radiation, from about 53 nA without the scintillator film to about 102 nA with the scintillator located on top of the PD, proves the suitability of the developed printed device for X-ray detection applicationsThe authors thank FEDER funds through the COMPETE 2020 Programme and National Funds through FCT-Portuguese Foundation for Science and Technology under Strategic Funding UID/FIS/04650/2013 and projects PTDC/EEI-SII/5582/2014, PTDC/CTM-ENE/5387/2014 and in the framework of EuroNanoMed 2016 call, Project LungChek ENMed/0049/2016. J.O. and V.C. thank the FCT for the SFRH/BD/98219/2013 and SFRH/BPD/97739/2013 grants, respectively. The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R. Financial support from the Basque Government Industry Department under the ELKARTEK program is also acknowledged. The authors thank Iain McCulloch and Martin Heeney from Flexink for providing the OSC. Dirk Rittrich (Department Layer Deposition at Fraunhofer ENAS) is acknowledged for the FIB/SEM analysis and the sample preparation. R.D.R acknowledges the DFG Unit FOR1317 SMINT, the Cluster of Excellence, and the Tomsk Polytechnic University Competitiveness Enhancement Program grant TPU CEP_IHTP_73\2017. This work was performed in the context of the European COST Action MP1302 Nanospectroscopy.info:eu-repo/semantics/publishedVersio

Effect of the carbon nanotube surface characteristics on the conductivity and dielectric constant of carbon nanotube/poly(vinylidene fluoride) composites

Commercial multi-walled carbon nanotubes (CNT) were functionalized by oxidation with HNO3, to introduce oxygen-containing surface groups, and by thermal treatments at different temperatures for their selective removal. The obtained samples were characterized by adsorption of N2 at -196°C, temperature-programmed desorption and determination of pH at the point of zero charge. CNT/poly(vinylidene fluoride) composites were prepared using the above CNT samples, with different filler fractions up to 1 wt%. It was found that oxidation reduced composite conductivity for a given concentration, shifted the percolation threshold to higher concentrations, and had no significant effect in the dielectric response

Roadmap on printable electronic materials for next-generation sensors

The dissemination of sensors is key to realizing a sustainable, ‘intelligent’ world, where everyday objects and environments are equipped with sensing capabilities to advance the sustainability and quality of our lives—e.g., via smart homes, smart cities, smart healthcare, smart logistics, Industry 4.0, and precision agriculture. The realization of the full potential of these applications critically depends on the availability of easy-to-make, low-cost sensor technologies. Sensors based on printable electronic materials offer the ideal platform: they can be fabricated through simple methods (e.g., printing and coating) and are compatible with high-throughput roll-to-roll processing. Moreover, printable electronic materials often allow the fabrication of sensors on flexible/stretchable/biodegradable substrates, thereby enabling the deployment of sensors in unconventional settings. Fulfilling the promise of printable electronic materials for sensing will require materials and device innovations to enhance their ability to transduce external stimuli—light, ionizing radiation, pressure, strain, force, temperature, gas, vapours, humidity, and other chemical and biological analytes. This Roadmap brings together the viewpoints of experts in various printable sensing materials—and devices thereof—to provide insights into the status and outlook of the field. Alongside recent materials and device innovations, the roadmap discusses the key outstanding challenges pertaining to each printable sensing technology. Finally, the Roadmap points to promising directions to overcome these challenges and thus enable ubiquitous sensing for a sustainable, ‘intelligent’ world

Roadmap on energy harvesting materials

Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere

Influence of glucose, sucrose, and dextran coatings on the stability and toxicity of silver nanoparticles

Aqueous colloids, consisting of 15–30 nm-sized silver nanoparticles (Ag NPs), were prepared using the reducing and stabilizing abilities of glucose, sucrose, and dextran. The long-term stability of coated Ag NPs increases from glucose over sucrose to dextran, i.e., with the increase of the molecular weight of carbohydrate molecules. The density functional theory (DFT) calculations of the partial atomic (Mulliken) charges and adsorption energies are applied to explain the enhanced stability of coated Ag NPs. All coated Ag NPs have a significantly broader concentration range of nontoxic behavior toward pre-osteoblast cells than bare Ag NPs prepared using sodium borohydride. The carbohydrate-coated Ag NPs display the same level of toxic ability against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria as bare Ag NPs. The differences in toxicity mechanism of the coated and bare Ag NPs are a consequence of the absence and presence of co-occurring Ag+ ions in examined dispersion, respectively

Piezoresistive sensors for force mapping of hip-prostheses

The success of artificial prosthetic replacements depends on the fixation of the artificial prosthetic component after being implanted in the thighbone. The materials for fixation are subject to mechanical stresses, which originate permanent deformations, incipient cracks and even fatigue fractures. This work shows the possibility of monitoring the mechanical stress over time in prosthesis. In this way, highly sensitive silicon thin-film piezoresistive sensors were developed attached to prosthesis and their results compared with commercial strain gauge sensors. Mechanical stress-strain experiments were performed in compressive mode, during 10,000 cycles. Experimental data was acquired at mechanical vibration frequencies of 0.5 Hz, 1 Hz and 5 Hz, and sent to a computer by means of a wireless link. The results show that there is a decrease in sensitivity of the thin-film silicon piezoresistive sensors when they are attached to the prosthesis, but this decrease does not compromise its monitoring performance. The sensitivity, compared to that of commercial strain gauges, is much larger due to their higher gauge factors (-23.5), when compared to the GFs of commercial sensors (2).This work is funded by FEDER funds through the "Programa Operacional Factores de Competitividade – COMPETE" and by national funds arranged by FCT- Fundação para a Ciência e a Tecnologia, project references NANO/NMed-SD/0156/2007, PTDC/CTM/73030/2006 and PTDC/CTM/69316/2006. The authors also thank support from the COST Action MP1003, 2010 ‘European Scientific Network for Artificial Muscles’. VS, VC and MSM thank the FCT for the SFRH/BPD/63148/2009, SFRH/BD/48708/2008 and SFRH/BD/60713/2009 grants, respectively. CR thanks the IINL for a financial support via a PhD

Poly(vinylidene fluoride-co-hexafluoropropylene) based tri-composites with zeolite and ionic liquid for electromechanical actuator and lithium-ion battery applications

In order to improve the multifunctionality of polymer composites for advanced applications a novel tri-composite material is presented based on the inclusion of MFI zeolite and the ionic liquid (IL) 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]) in an electroactive poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer matrix. Tri-composites were produced by solvent casting with a relative overall filler content up to 40 wt.%. A compact film morphology is obtained, and the polymer degradation temperature and degree of crystallinity are independent on the filler content and type. On the other hand, the polymer crystalline phase depends on the presence of the IL but is independent of its content. Regarding the mechanical properties, it is observed that the IL has a plasticizing effect with a significant contribution to the reduction of the Young's modulus from 151 MPa for the pristine polymer to 92 MPa for the 30 wt.%/10 wt.% IL/MFI content sample. A high ionic conductivity value at room temperature of 3.9 × 10−5 S.cm−1 was obtained for the tri-composite with the highest IL content (30 wt.%/10 wt.% IL/MFI). The tri-composite system was studied as solid polymer electrolyte (SPE) for battery and bending actuator applications, demonstrating the multifunctionality of the material. The sample with the best cycling performance was observed for the highest MFI content (10 wt.%/30 wt.% IL/MFI) with a discharge capacity value of 110 mAh.g−1 and maintaining almost 80% of its initial capacity after 30 cycles at the C/10 rate. Regarding to the bending performance, the best bending actuation was detected for highest IL content (30 wt.%/10 wt.% IL/MFI), related to the ionic conductivity of the sample. Thus, it is demonstrated that the new tri-composite system, due to its tunable characteristics as a function of the relative IL and zeolite contents, is suitable for a next generation of multifunctional polymer composite materials for advanced applications.The authors thank FCT (Fundac ~ao para a Ci encia e a Tecnologia) for financial support under the framework of Strategic Funding grants UIDB/04650/2020, UID/FIS/04650/2021, UID/EEA/04436/2021 and UID/QUI/0686/2021; and support from FEDER funds through the COMPETE 2020 Programme (projects PTDC/FIS-MAC/28157/2017 and POCI-01-0145-FEDER-007688) and MIT-EXPL/TDI/0033/2021, POCI01-0247-FEDER-046985. Grants SFRH/BD/140842/2018 (J.C.B.), 2021.07361.BD (R.S.P.), and SFRH/BPD/121526/2016 (D.M.C) and contracts under the Stimulus of Scientific Employment, Individual Support CEECIND/00833/2017 (R.G.) and 2020.04028 CEECIND (C.M. C.) are acknowledged. Financial support from the Basque Government under the ELKARTEK program is also acknowledged

Bioinspired three-dimensional magnetoactive scaffolds for bone tissue engineering

Bone tissue repair strategies are gaining increasing relevance due to the growing incidence of bone disorders worldwide. Biochemical stimulation is the most commonly used strategy for cell regeneration while the application of physical stimuli such as magnetic, mechanical or electrical fields is a promising, however scarcely investigated field. This work reports on novel magneto-active 3D porous scaffolds, suitable for effective proliferation of osteoblasts in a biomimetic microenvironment. This physically active microenvironment is developed through the bone mimicking structure of the scaffold combined with the physical stimuli provided by a magnetic custom-made bioreactor on a magneto-responsive scaffold. Scaffolds are obtained through the development of nanocomposites comprised of a piezoelectric polymer, poly(vinylidene fluoride) (PVDF), and magnetostrictive particles of CoFe2O4 using a solvent casting method guided by the overlapping of nylon template structures with three different fibre diameter sizes (60, 80 and 120 µm), thus generating 3D scaffolds with different pore sizes. The magneto-active composites show a structure very similar to trabecular bone with pore sizes ranging from 5 µm to 20 µm, owed to the inherent process of crystallization of PVDF with the NPs, interconnected with bigger pores, formed after removing the nylon templates. It is found that the materials crystallize mainly in the electroactive -phase of PVDF and that promote the proliferation of pre-osteoblasts through the application of magnetic stimuli. This phenomenon is attributed to both local magnetomechanical and magnetoelectric response of the scaffolds, which induce a proper cellular mechano- and electro-transduction process.This work was supported by national funds through the Fundacao para a Ciencia e Tecnologia (FCT) and by ERDF through COMPETE2020-Programa Operacional Competitividade e Internacionalizacao (Pod) in the framework of the Strategic Programs UID/FIS/04650/2019 and projects LungChek ENMed/0049/2016, PTDC/EMD-EMD/28159/2017, and PTDC/BTM-MAT/28237/2017. M.M.F. and D.M.C. thank FCT for the grants SFRH/BPD/121464/2016 and SFRH/BPD/121526/2016, respectively. Finally, the authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Departments under the ELKARTEK and PIBA (PIBA-2018-06) programs, respectively. We would like to acknowledge Dr. Raul Machado for performing FTIR measurements.info:eu-repo/semantics/publishedVersio

Dielectric relaxation and ferromagnetic resonance in magnetoelectric (Polyvinylidene-fluoride)/ferrite composites

In this work the dielectric properties and ferromagnetic resonance of Polyvinylidene- uoride embedded with 10 wt. % of NiFe2O4 or Ni0.5Zn0.5Fe2O4 nanoparticles are presented. The mechanisms of the dielectric relaxation in these two composites do not differ from each other. For more precise characterization of the dielectric relaxation, a two dimensional distribution of relaxation times was calculated from the temperature dependencies of the complex dielectric permittivity. The results obtained from the 2D distribution and the mean relaxation time are found to be consistent. The dynamics of the dielectric permittivity is described by the Arrhenius law. The energy and attempt time of the dielectric relaxators lie in a narrow energy and time region thus proving that the single type chains of polymer are responsible for a dispersion. The magnetic properties of the composites were investigated using the fer- romagnetic resonance. A single resonance line was observed for both samples. From the temperature dependence (100 K - 310 K) of the resonance eld and linewidth, the origin of the observed line was attributed to the NiFe2O4 and Ni0.5Zn0.5Fe2O4 superparamagnetic nanoparticles. By measuring lms at dif- ferent orientations with respect to the external magnetic eld, the angular dependence of the resonance was observed, indicating the magnetic dipolar in-plane interactions.This work was supported by Lithuanian Research Council under the project MIP-068/2012 and by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2011, project PTDC/CTM-NAN/121038/2010 and the project MateproOptimizing Materials and Processes, ref. NORTE-07 − 0124-FEDER-000037, cofunded by the Programa Operacional Regional do Norte (ON.2 O Novo Norte), under the Quadro de Referncia Estratgico Nacional (QREN), through the Fundo Europeu de Desenvolvimento Regional (FEDER). P. Martins thanks the FCT for the grant FCT-DFRH SFRH/BPD/96227/2013