Polymeric clear aligners are increasingly used in orthodontics due to their aesthetic appeal and comfort. When placed in the oral cavity, they are continuously exposed to challenging conditions such as temperature fluctuations and changes in pH. The mechanical properties of these aligners are strongly influenced by temperature and liquid absorption. This study employs Dynamic Mechanical Analysis (DMA) to evaluate the effect of a saline solution (0.9 % NaCl) on the polyurethane-based material Tera Harz TC-85.

DMA was performed over a temperature range of 20 °C to 88 °C, measuring storage modulus (E′), loss factor (tan δ), and glass transition temperature (Tg). Aging the material under laboratory conditions for three months showed no significant effect on its mechanical properties. However, exposure to the saline solution led to a marked decrease in E′, tan δ, and Tg, indicating that the saline solution acted as a plasticizer. At 35 °C, the modulus of soaked samples decreased by 59 % compared to as-prepared samples. Further soaking beyond five days did not produce additional changes. The plasticization process was reversible; after three days of drying, the material's properties were almost fully restored.

Saline solution acts as a reversible plasticizer for Tera Harz TC-85, reducing its stiffness and Tg. Given that the average oral cavity temperature (34 °C) is near or above the Tg of soaked samples (30 °C – 31.5 °C), their mechanical properties degrade during use. This can lead to reduced effectiveness of orthodontic aligners.

Dental implants are widely used to replace missing teeth. Typically cylindrical or tapered with threads, they are commonly made of commercially pure titanium (CP Ti) or its Ti6Al4V alloy. These implants are osseointegrated, forming a rigid connection with the surrounding alveolar bone. However, unlike natural teeth, they lack critical periodontal structures such as the periodontal ligament (PDL) and cementum. This absence can lead to stress concentration, bacterial infiltration, and increased risk of implant failure. These limitations underscore the need for bioinspired designs that replicate the structural and functional integration of natural teeth. This study introduces a fibrointegration concept inspired by the natural tooth-PDL-bone interface. Zirconia was explored as a promising alternative to titanium due to its high mechanical strength, excellent biocompatibility, and effective osseointegration. Its tooth-like color improves aesthetics and reduces plaque accumulation. Zirconia specimens with internal micro-channels and an external porous surface were designed to mimic dentinal tubules and cementum functions, respectively. These were fabricated using CAD/CAM and dip-coating techniques, then characterized. The impact of these structural features on cell behavior was assessed using human periodontal ligament fibroblasts (hPLFs) in vitro. Electrical impedance spectroscopy was performed between 1 and 100 kHz to gain further insights into cell adhesion and activity. Results showed that channel-embedded porous zirconia surfaces exhibited superhydrophilic behavior and strong capillary effects, facilitating rapid fluid uptake-key factors for fibroblast attachment and guided growth. All specimens demonstrated biocompatibility with hPLFs, with the highest fibroblast proliferation observed on surfaces combining both micro-channels and porosity. SEM images confirmed cell embedding within the porous structure. Electrical impedance measurements after 3 days of culture revealed the highest impedance values for the channel-porous specimens, indicating enhanced cell adhesion, migration, and spreading. These findings show that channel-porous zirconia surfaces can smartly guide fibroblast growth, supporting the design of bioinspired implants for functional fibrointegration.

The increasing presence of emerging contaminants such as pharmaceuticals in water systems poses a significant environmental challenge due to their persistence and resistance to conventional treatment methods. Trimethoprim, a widely used antibiotic, is a frequent pollutant in wastewater and surface waters, raising concerns due to its bioactivity and toxicity. Advanced oxidation processes (AOPs), particularly photocatalysis, sonocatalysis, and their hybrid form sonophotocatalysis, offer promising strategies for degrading such contaminants through the generation of reactive oxygen species (ROS). Photocatalysis involves the use of a light-activated semiconductor catalyst that generates ROS under UV or visible light. Sonocatalysis relies on ultrasonic vibrations to excite piezoelectric materials and produce ROS. Bismuth tungstate (Bi₂WO₆), a layered Aurivillius oxide with a suitable bandgap (2.6 - 2.8 eV), exhibits enhanced photocatalytic performance due to its ability to promote charge carrier separation. WS₂, a two-dimensional transition metal dichalcogenide, offers strong piezocatalytic efficiency due to its mechanical flexibility, noncentrosymmetric monolayer structure, and highly polarizable W-S bonds, which improve charge separation under mechanical strain.

Integrating Bi₂WO₆ and WS₂ forms a heterojunction that enhances charge transfer and suppresses electron–hole recombination, synergistically boosting piezophotocatalytic performance. In this study, we developed a membrane system based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), incorporating a Bi₂WO₆@WS₂ powder heterojunction for the sonophotocatalytic degradation of trimethoprim antibiotic. The wt. % ratio of PVDF to Bi₂WO₆@7wt%WS₂ was equal to 70:30. The composite membranes were characterized using XRD, TEM, XPS, Raman, DRS UV-Vis, PL, EIS, Mott–Schottky, and photocurrent, revealing favorable structural, optical, and electrochemical properties.

The composite demonstrated high catalytic efficiency, reusability, and stability, effectively degrading trimethoprim in both distilled and river water. A possible degradation mechanism under combined light and ultrasonic treatment was proposed. This work presents a flexible membrane platform that combines piezo- and photocatalytic activity for advanced water treatment applications.

An important characteristic of thermoelectric materials, i.e., the power factor (PF σS², σ—specific electrical conductivity, S—Seebeck coefficient), often has extreme values ​​depending on the absolute temperature, composition, concentration of charge carriers, Fermi energy, etc. In this work, PF–T dependence is considered. In some cases, it has a minimum in others, a maximum, and in some cases, both. For practical purposes, it is of interest to determine the maxima of this thermoelectric characteristic, which is included in the expression of the figure of merit, ZT.

A mathematical approach to the issue has been made. In particular, it turned out that despite the presence of several variable quantities in the formulas used, there was no need for the use of the Lagrange multiplier method; the usual calculation could be applied instead.

To compile formulas from the literature relating the absolute temperature, effective mass, and concentration of charge carriers, the following expression for the Seebeck coefficient can be obtained: Using f(S), we will get PF AT^3/2, where A= and S_r is the reduced Seebeck coefficient.

For SiGe samples under study, the empirical result is (PF)_max 1.42∙10⁸A_maxT^3/2.

The dependence (ZT)_max– B is then investigated (B=ZT/B_S,

B_S=[( e^2−Sr)/(1+e^−5(Sr−1))]+[3.29S/(1+e^5(Sr−1))] – scaled power factor, S_r=(q_e/k_B)│S│ – reduced Seebeck coefficient). It can be described by the expression (ZT)_max≅3.2B+0.05.

The dependence of (ZT)_max - B* (generalized parameter of material) is also investigated. A formula is used to calculate the values of B*, which contains the quantities of band gap (E_g), specific electrical conductivity, a scaled parameter, and thermal conductivity (k): B* 7.755·10^-4E_g k^-1. By calculating B and B* parameters, the maximum value of the figure of merit for almost anythermoelectric material can be approximately estimated.

Introduction

Bacterial nanocellulose is a biocompatible and non-immunogenic biopolymer that offers several advantages for regenerative medicine such as high porosity and purity [1]. Therefore, adding bacterial cellulose nanofibers as part of 3D printing inks is being explored to manufacture adapted-to-patient biomaterials with advanced properties for tissue repair.

Methodology

In this work, bacterial cellulose nanofibers were manufactured by a well-established protocol from the bacterial strain K. xylinus [1 - 3] and were added to methylcellulose inks to fabricate 3D-printed scaffolds. Polyurea crosslinking and superparamagnetic iron oxide nanoparticle loading were explored to improve the performance of the biomaterials. Confocal, scanning and transmission electron microscopies, as well as printing fidelity and porosity analysis of the scaffolds, were performed. Cell studies with murine fibroblasts and hemolytic activity tests with human blood were also employed to biologically characterize the biomaterials.

Results and Discussion

Bacterial cellulose nanofibers were manufactured with a diameter close to 50 nm. Improved volume shrinkage and printing fidelity were observed after loading the bacterial nanocellulose into 3D-printed methylcellulose scaffolds. Doping with superparamagnetic iron oxide nanoparticles and crosslinking with polyurea enhanced the physicochemical performance of the biocompatible formulations. The results obtained may motivate future research into the use of these biomaterials as soft tissue grafts.

Conclusions

Bacterial nanocellulose-loaded scaffolds exhibited good values of cell compatibility, hemolytic activity, porosity and printing fidelity. Polyurea crosslinking and superparamagnetic iron oxide nanoparticle loading improved the suitability of the biomaterials for regenerative medicine applications.

Acknowledgments

This work was funded by MICIU/AEI/10.13039/501100011033 [grants PID2023-151340OBI00, PDC2022-133526-I00 and PDC2023-145826-I00], Xunta de Galicia [ED431C2022/2023], ERDF/EU and European Union NextGenerationEU/PRTR. A. I.-M. acknowledges Xunta de Galicia for her postdoctoral fellowship [ED481B-2025/032].

References

[1] Malandain N et al, 2023, 10.1021/acsabm.3c00126.

[2] Iglesias-Mejuto et al, 2024, 10.1007/s10570-023-05601-1.

[3] Iglesias-Mejuto et al, 2025, 10.1021/acsami.5c08389.

Quoxaline and its derivatives can be used as acceptors in the design of fluorescent materials.Two analogues, 4,4-(2,3-diphenyl-quinoxalin-6,7-diyl)bis(N,N-diphenyl-phenylamine) (2TPA-DPQ) and 3,3-(2,3-diphenyl-quinoxalin-6,7-diyl)bis(9-phenyl-9H-carbazole) (2PC-DPQ) were designed and synthesized. 2TPA-DPQ and 2PC-DPQ possessed donor-acceptor structures, in which triphenylamine and N-phenyl carbazole acted as the electron donors while 2,3-diphenyl quinoxaline served as the electron acceptor, respectively. The molecular structures of the compounds were confirmed by NMR, mass spectrometry and single crystal XRD. Fluorescence emission and UV absorption spectra were used to study intramolecular charge transfer (ICT), piezofluorochromic, and sensing properties of two compounds. The results indicated that 2TPA-DPQ and 2PC-DPQ exhibited typical ICT characteristics with dipole moment gaps of 23.0 D and 21.4 D between the excited and ground state, respectively. 2PC-DPQ showed reversible piezofluorochromic property with a fluorescence spectrum change of 15 nm upon grinding and heating the solid sample. In contrast, 2TPA-DPQ demonstrate selective sensing property to Cu²⁺ ions and could be used as a fluorescent probe of Cu²⁺. The fluorescence of 2TPA-DPQ was completely quenched when the concentration of Cu²⁺ ions was 7 times or more than the concentration of 2TPA-DPQ.This study provides a reference for the design, synthesis and application of electron donor substituted quinoxaline derivatives.

The rehabilitation process of asphalt pavement using the milling and filling technique can cause several environmental problems due to either the disposal of milled asphalt mix or the exploitation of new deposits of natural resources. One alternative to reduce carbon emissions in road construction is the reuse this milled material in the construction of new pavement layers. This paper investigates the influence of asphalt content of reclaimed asphalt pavement (RAP) on the physical and mechanical characteristics of the tested mix. Several series of specimens were made from three granular mixes, series 1: specimens made from unbound granular materials (UGM); series 2: specimens based on cement-bound granular materials (CBGM);and series 3: specimens made with a mix of UGM and different proportions (10%, 20%, 30%) of RAP. Physical and mechanical characterization tests of the prepared samples were carried out on all samples at 28 days of curing. The results show that mechanical strengths decrease with an increase in the RAP aggregate content. The modulus of the RAP-based specimens is between the modulus of UGM samples and that of CBGM. The best physical and mechanical characteristics of the recycled aggregate mix are obtained for a proportion of 10% RAP in the mix. Furthermore, an assessment of the carbon emission mitigation potential due to the replacement of new aggregates with RAP, using a life cycle analysis (LCA), shows a significant reduction in carbon emissions from 10% RAP in the granular mix. This work aims to advance policy discussions on integrating circular economy principles into infrastructure standards, with a focus on emissions reduction as a key indicator of sustainable road preservation.

The rising demand for multifunctional coatings in healthcare, smart textiles, and filtration technologies has driven interest in polymer-based thin films with integrated antibacterial, mechanical, and electrical properties. This study presents a scalable Layer-by-Layer (LbL) nanocoating approach using water-soluble polyelectrolytes and carbon nanotubes (CNTs). Branched polyethylenimine (BPEI, pKa ~9.5) and poly(acrylic acid) (PAA, pKa ~4.5) were selected as the polycation and polyanion, respectively, exhibiting pH-dependent ionization behavior. Optimal LbL conditions were achieved at pH 10 for BPEI and pH 4 for PAA to ensure strong electrostatic interactions and robust multilayer formation. CNTs were incorporated into the PAA solution to form conductive interlayers, enhancing both electrical conductivity and mechanical durability.

Antibacterial activity was assessed using Staphylococcus aureus (ATCC 6538), following the KS K 0693 standard. BPEI, PAA, and PAA+CNT solutions were tested, with all showing inhibition zones. BPEI exhibited the strongest antibacterial effect due to its high positive charge density. Subsequently, 20 bilayers of coatings were deposited on glass coverslips via spray-assisted LbL using BPEI/PAA and BPEI/PAA+CNT. Samples underwent three post-treatments: untreated, UV exposure, and autoclaving. All coated samples maintained antibacterial activity, with CNT-containing films retaining efficacy even after sterilization, suggesting synergistic antibacterial effects from CNT–microbe interactions.

Surface analysis revealed increased roughness and interfacial adhesion in CNT-containing coatings, contributing to improved durability and reusability. Electrical measurements confirmed enhanced conductivity, highlighting their potential in smart interfaces, antistatic films, and biosensing platforms.

This work demonstrates a versatile and scalable strategy for developing multifunctional antibacterial nanocoatings using pH-tuned LbL assembly and CNT integration, offering promising applications in biomedical, industrial, and consumer-oriented technologies.

Metal-doped ZnO nanoparticles were prepared using the co-precipitation synthesis method to analyze their optical and structural properties. Five different samples with the formula A_XZn_1-XO (where A = Ni, Cu, Co, Cd, Sr, and X = 0.01) were prepared by using the same doping concentration. X-ray diffraction (XRD) measurement confirmed that all prepared samples maintained a single-phase structure without having any secondary oxide peaks. Fourier-transform infrared (FTIR) spectroscopy showed the presence of functional groups such as carboxylate, zinc carboxylate, and hydroxide. The surface morphology of the samples was examined using scanning electron microscopy (SEM), which revealed the formation of both nanoparticles and nanorods. The particle sizes were approximately in the range of 50 nm and varied depending on the dopant used. The optical properties, particularly the electronic and optical band gaps, were analyzed using UV-Visible absorption spectroscopy and Tauc plots. It was calculated that the band gap increased from 3.37 eV in pure ZnO to about ~3.8 eV in the doped samples, depending on the dopant. These results suggest that the type of metal dopant has a significant impact on the optical behavior of ZnO. The doped ZnO nanoparticles demonstrate promising potential for use in various applications, including transparent electronics, UV LEDs and lasers, UV-blocking coatings, photocatalysis, and consumer products such as sunblock and sunglasses.

Since the beginnings, the reliability problems draw attention in the field of electrical devices. The needs to understand the failure mechanism of unreliable components is permanent. One of the most challenging problems is the thermomechanical stress, which is considered mainly due to the mismatch of the thermal expansion coefficient of the different components. Temperature and mechanical stress are important variables, that must be monitored during the entire production process, firstly, and working phase, secondly. Indeed, local deviations can lead to uncontrolled changes. To evaluate the stress effects, Raman spectroscopy measurements were performed.

In this work, the local stress was analyzed in three case studies: the active layer of commercially available GaN-based LEDs and in Silicon and Silicon Nitride chips. Specifically, great attention was used examining how stress varies depending on bonding processes, such as temperature and pressure of soldering, as well as the impact of bonding and substrate materials on stress evolution. Raman spectroscopy was selected as the primary technique: it is non-destructive and allows for the analysis of materials both before and after bonding. The Raman investigation was performed on both metal and semiconductor properties of the materials of the integrated circuits. Stress phenomena were determined by 2D Raman mapping of the surface, in a wide temperature range, from -50 to 180° C. From the determination of the Raman peak position of Silicon, centered around 520 cm^-1, Si3N4, centered around 865 cm^-1, and GaN, centered around 568 cm^-1, the presence of tensile and compressive stresses on the samples were evaluated. Finally, the results were correlated to the process parameters to suggest possible optimization procedure to reduce the reliability problems in the structure of optoelectronic devices.