Search Results (247)

Background/Objectives: One of the ongoing clinical constraints is limiting microbial growth on prostheses, justifying the need for material surface enhancements to reduce microbial complications. This study aimed to investigate a potentially applicable and reproducible coating technique to overcome clinical microbial challenges. Methods: Silver (Ag) nanoparticles (NPs) were applied to three types of materials through spray, spin, and dip coating techniques. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray fluorescence (EDXRF), and inductively coupled plasma optical emission spectroscopy (ICP-OES) were performed. Subsequent optimization of spray numbers was determined. Antimicrobial performance of one- and three-layered coatings was evaluated through agar diffusion, direct contact, and adhesion (time-dependent) assays against Pseudomonas aeruginosa (P. aeruginosa). Results: Spray coating exhibited superior coating uniformity. In total, 15 sprays were determined as an effective number for a single-layer coating. EDS confirmed Ag NP presence; FTIR revealed no chemical alteration. Disk diffusion tests showed no inhibition zones. Adhesion and direct contact tests displayed antibacterial activity. The effect was superior in direct contact test. Short-term time-dependent adhesion test of one-layer coating of acrylic and silicone had a consistent decrease in bacterial amount, whilst zirconium had only a strong initial activity. In general, the three-layer coating did not reveal a higher antimicrobial activity, suggesting that the increase in layering can negatively impact surface effectiveness. Conclusions: Spray coating of Ag NPs represents a potentially feasible and relevant strategy for enhancing the antibacterial properties of dental and maxillofacial prosthetic materials without compromising their inherent physicochemical characteristics, pending further cytotoxicity and in vivo validation. Full article

In this work, a non-standardized hypereutectic aluminum–silicon alloy AlSi21Cu5MgCr intended for the automotive industry is presented. The modification of the alloy is performed with the conventional modifier phosphorus in an amount of 0.04 wt%. The applied metallurgical treatment is the basis for the obtained modified structure. It has been established that after conducting the T6 heat treatment, the free silicon crystals are reduced to 26.9 µm, and the eutectic silicon crystals are spherical in shape and have dimensions not exceeding 8 µm. The macrohardness of the studied alloy is 168.5HV_10/10, a value significantly higher than that required for this type of alloy, which is in the range of 95 ÷ 137 HV (90 ÷ 130 HB). The microhardness of the α-phase in the composition of the eutectic is 154 µHV_50/10, which indicates that after quenching a saturated solid solution was fixed, and during the artificial aging process secondary strengthening phases were formed and separated. A CrAlN hard coating was deposited on the alloy surface. The mechanical properties of the coating were characterized by a hardness of 14 GPa, whereas the AlSi21Cu5MgCr substrate had a hardness of 2 GPa. The results showed considerable improvement of the hardness of the new alloy and well-tuned elastic–plastic properties. The obtained adhesive properties are compatible with this class of materials. The composition of the CrAlN hard coating is homogeneously distributed on the alloy surface and the morphology is improved. The investigations showed that CrAlN hard coatings could successfully be applied for the modification of the surface of AlSIMgCu alloys. Full article

With the miniaturization of electronic devices, the demand for high-efficiency thermal management materials has become increasingly urgent. Although traditional high-filler random blending composites can enhance thermal conductivity, they often do so at the expense of mechanical properties and lightweight advantages. Therefore, constructing oriented thermal conduction networks at low filler loadings has become a core challenge in current research. This study proposes an interface engineering strategy based on a tannic acid (TA) molecular bridging layer to modify silicon carbide (SiC). By leveraging the self-polymerization and strong adhesion properties of TA, a dense fish scale SiC coating was formed on the surface of highly oriented woven cellulose acetate (WF) through a simple impregnation process. After compositing with a polyurethane (PU) matrix, the obtained WF/TA/SiC/PU exhibits anisotropic thermal conductivity. It has an axial thermal conductivity of 0.44 W/mK, an increase of 411% over PU, and the decomposition temperature has increased by 18.2 °C. Additionally, the composite axial thermal response rate significantly outperforms both the radial direction and PU. This research demonstrates a new approach for achieving high-efficiency thermal management at low filler loadings, providing a scalable pathway for the development of sustainable, lightweight, and high-performance anisotropic heat dissipation devices. Full article

To overcome the inherently low temperature sensitivity of fiber Bragg gratings (FBGs) in engineering applications under low-temperature conditions, a sensitivity-enhanced FBG temperature sensor based on a polytetrafluoroethylene (PTFE) encapsulation sleeve was developed. Four adhesive materials—silicone thermal grease, polydimethylsiloxane (PDMS), epoxy resin, and modified acrylic ester—were employed to package the FBG within the PTFE sleeve to improve its temperature sensitivity. Thermal stress simulations of the proposed sensor structure were carried out using COMSOL Multiphysics^® 6.2, and the simulation results showed good agreement with the experimental data. Based on the experimental results, the sensitivity-enhancement effects of PTFE combined with different adhesives, as well as the influences of the PTFE sleeve length and wall thickness, were systematically investigated. The results indicate that, within the temperature range of −35 °C to 15 °C, increasing both the length and thickness of the PTFE sleeve can effectively improve the temperature sensitivity of the sensor. When epoxy resin was used as the encapsulating adhesive, the sensor achieved a maximum sensitivity of 117.4 pm/°C, corresponding to a 13.19-fold increase compared with that of a bare FBG sensor. This sensitivity-enhancing packaging structure significantly improves both the temperature sensitivity and linearity of FBG temperature sensors, while also substantially reducing fabrication costs. Full article

Conventional flexible substrates for strain sensors generally exhibit good flexibility and processability; however, their limited heat resistance restricts their long-term application in high-temperature environments. Aiming at the problem of insufficient heat resistance of high-temperature flexible strain sensing matrix, triphenyltetramethylcyclotrisiloxane (P₃), trimethyltrivinylcyclotrisiloxane (V₃) and octamethylcyclotetrasiloxane (D₄) were used as raw materials in this paper. Methyl vinyl phenyl silica gel (MVMPS) with high phenyl and vinyl content was prepared by anionic ring-opening polymerization, and condensed with KH-570 (3-Methacryloxypropyltrimethoxysilane) to obtain a condensed modified gel (C-MVMPS). Subsequently, a methyl vinyl phenyl silicone rubber composite was fabricated using fumed silica as the reinforcing filler and Si69 as the coupling agent and vulcanization assistant. In addition, flake silver powder was incorporated to prepare an Ag/MVMPS conductive adhesive, and a sandwich-structured strain sensor with a silicone rubber/Ag-MVMPS conductive adhesive/silicone rubber configuration was fabricated. The synthesized methyl vinyl monophenyl silicone gum exhibited a number-average molecular weight of 170,449, a phenyl content of 25.19%, and a vinyl content of 24.44%. The composite showed the best overall performance at 3 phr (parts per hundred of rubber) Si69 (Bis(gamma-triethoxysilylpropyl) tetrasulfide) and 30 phr SiO₂ (Fumed silica), with a 5% weight-loss temperature (T_5%) of 367.14 °C and a 10% weight-loss temperature (T_10%) of 529.6 °C. The prepared sandwich-structured sensor exhibited clear and stable resistance responses within the strain range of 10–80%. The sensitivity increased with increasing strain, and good reproducibility was maintained under different loading rates. Moreover, the sensor still exhibited continuous and distinguishable cyclic responses after 1000 cycles at 20% strain. These results provide an experimental basis and a feasible design strategy for the application of methyl vinyl phenyl silicone rubber in high-temperature flexible strain sensors. Full article

Silicone pressure-sensitive adhesives are a prominent group of adhesive materials used in many contemporary industrial sectors. This is due to their high resistance to difficult operating conditions, especially high temperatures. They are used, among other areas, in the automotive industry or in power engineering, as fastening or insulation systems operating at high temperatures. Previous studies have demonstrated the beneficial effect of mineral fillers on further increases in thermal resistance and dimensional stability of silicone pressure-sensitive adhesives. This paper presents the results of research on the effect of adding rose quartz as a filler to silicone pressure-sensitive adhesives based on polydimethylsiloxanes, on the adhesion parameters of the obtained adhesives and their thermal resistance and dimensional stability at elevated temperatures. The self-adhesive tapes obtained showed increased resistance and thermal stability while maintaining the required performance parameters. Among the tested compositions, optimal PSA parameters were achieved for Q2-7358 resin filled with 0.5 pph of rose quartz particles: adhesion exceeded industrial requirements by more than 15%, and tack met those requirements. Furthermore, low (and consistent) shrinkage (0.4% after one week) and cohesion—evaluated as hold time > 72 h—were recorded. As the most important parameter for studied compositions, thermal resistance (SAFT) substantially increased (>225 h) in comparison to neat resin (150 h). Full article

The development of sustainable encapsulation materials with tunable thermomechanical properties remains a critical challenge for photovoltaic reliability. Currently, the mainstream encapsulant for polycrystalline silicon solar cells is crosslinked EVA (Ethylene-Vinyl Acetate), which complicates the end-of-life recycling and reuse of modules. There is an urgent need to develop a novel encapsulant that combines excellent barrier properties with thermoplastic recyclability. Herein, we report a novel series of thermally decomposable CO₂-based thermoplastic polyurethane (PPC-TE) films engineered through the rational design of soft and hard segments. Utilizing polycarbonate diol (PPCDL) and polyether glycol (PEG) as soft segments, we systematically tailor material properties by modulating PEG-to-PPCDL ratios (5–20 wt%) and PEG molecular weights (1000–4000 g/mol). The optimized PPC-TE films exhibit excellent transmittance (>90%), adjustable glass transition temperature (T_g: 35.1 °C~11.6 °C), and remarkable mechanical adaptability (51~92 HA). The PPC-TE films exhibit water vapor permeability (WVP) as low as 14.8 g·mm·m⁻²·day⁻¹ and oxygen permeability (OP) of 4.13 cc·mm·m⁻² day⁻¹ at 15 wt% PEG content, surpassing commercial ethylene–vinyl acetate (EVA) encapsulants. Notably, these films demonstrate fully thermal decomposition above 350 °C, facilitating eco-friendly photovoltaic device recycling. Superior adhesion to glass substrates is evidenced by peel strengths up to 37 N/cm (PPC-TE2000-20) and the shrinkage rate is as low as 3%. This work contributes to improving the long-term stability of solar cells and has the potential for large-scale production. Full article

Background/Objectives: Commercially available drug-eluting stents still suffer from poor blood compatibility, polymer coating delamination, polymer cracking and lack of stability during and after stent implantation that led to adverse events such as stent thrombosis and in-stent restenosis. This article highlights the advantages of using silicon nanofilament (SiNf) as an interface between stent surface and drug-in-polymer coating or bloodstream. Methods: Thin layer of SiNf was successfully formed on the surface of Co-Cr substrate via one-step simple method. For stent applications, sirolimus-in-poly(D,L-lactide) (PDLLA/SRL) matrix was coated on control and SiNf-modified Co-Cr substrates and the stability, cracking, and long-term degradation was compared. Blood compatibility studies were also compared between control and SiNf-modified Co-Cr substrates. Results: The morphology of the filaments showed nanosized structures with nano-gaps between the filaments which support mechanical interlocking of PDLLA/SRL coating and enhanced the coating stability with no coating delamination whereas, the control substrate presented 97% of coating delamination. The PDLLA/SRL coating on stent platform demonstrates smooth and uniform morphology without webbing between stent struts. After stent ballooning, the control stent presented cracking and peeling of the polymer coating from the surface whereas, the SiNf-modified stent did not show any signs of these unfavorable defects. Moreover, SiNf-modified surface showed reduced fibrinogen adsorption and lower number of platelet adhesion with round shape morphology. Conclusions: Overall, this suggests that modifying the metallic substrates with SiNf could act as a universal coating for reinforcing the polymer coating stability, prevent coating defects that accompany stent ballooning, and improve the blood compatibility of the material surfaces that could have various applications to medical implants and devices. Full article

The reliability of adhesive bonding to CAD/CAM resin composites is influenced not only by material composition and surface treatment but also by the testing methodology used to assess bond strength. However, the impact of different shear bond strength (SBS) test configurations remains insufficiently clarified. This study evaluated the influence of different surface pretreatment protocols and SBS test methods on the bonding performance of a self-adhesive resin cement to two CAD/CAM materials: a conventional particulate-filled composite (Cerasmart 270) and an experimental short glass fiber-reinforced composite (SFRC CAD). Specimens (14 × 12 × 3 mm; n = 80 per material) were ground with 320-grit silicon carbide paper and divided according to surface pretreatment: airborne-particle abrasion (APA) or APA followed by hydrofluoric acid application for 60 s (APA + HF). Each group was further subdivided based on the SBS test method using either resin cement cylinders fabricated with a custom transparent mold (diameter: 3.6 mm; height: 3 mm) or metallic cylinders cemented to the treated surface. Half of the specimens were tested after 48 h of water storage, while the remainder underwent hydrothermal aging by boiling in water for 16 h prior to testing. Material type, SBS test method, surface pretreatment, and aging significantly affected bond strength (p < 0.05). The metallic cylinder method produced higher SBS values than the transparent mold technique, particularly for SFRC CAD. APA + HF tended to reduce SBS in Cerasmart 270, particularly after aging, whereas SFRC CAD showed comparable or higher bond strength values with APA alone. Aging decreased SBS in most groups. Overall, bond strength was influenced by both material type and test methodology. Within the limitations of this study, airborne-particle abrasion alone may be sufficient for SFRC CAD materials, while additional HF treatment may not provide further benefit. These findings highlight the importance of considering both material characteristics and test configuration when interpreting laboratory bond strength data. Full article

Biofilms rapidly form on medical devices such as urinary catheters and surgical materials. These biofilms compromise patient safety and undermine infection prevention and control (IPC). Biofilms also reduce the effectiveness of antibiotics and disinfectants. As a result, they increase healthcare-associated infections and increase costs through device failure and the need for maintenance or replacement. Researchers are increasingly exploring biosurfactants (BSs) as surface coatings and cleaning additives to prevent microbial attachment and disrupt early biofilm formation on medical devices and healthcare-related surfaces. This review examines the translational potential of biosurfactants as preventive, disruptive, and adjunctive antibiofilm agents for medical devices and healthcare-related surfaces. Literature evidence on glycolipids (rhamnolipids, sophorolipids) and lipopeptides (surfactin) from static, flow-based, and microfluidic in vitro models that used clinically relevant materials, such as silicone and polydimethylsiloxane (PDMS), were examined. In our literature search, we focused on pathogens central to IPC, such as Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus spp., and Candida spp., and it was generally noted that BSs reduced microbial adhesion and delayed early biofilm formation on medical devices and healthcare-related surfaces. Significant evidence also suggests that they partially disrupt biofilms and improve antimicrobial penetration when co-applied, mainly through membrane disruption, destabilization of extracellular substances, interfering with quorum sensing, and synergistic and/or antagonistic interactions with other molecules. Their performance varied with class, formulation, hydrodynamic conditions, and microbial composition. BSs function better as preventive and adjunctive IPC tools than stand-alone antimicrobial agents and can help to reduce biofilm formation on devices and improve surface disinfection. However, translating this promise into practice demands more robust data on long-term safety, stability, and product quality. Full article

Fused filament fabrication (FFF) enables patient-specific scaffolds for critical-size bone defects, but most filaments are bioinert and difficult to functionalize at high particulate loadings due to segregation, agglomeration, clogging, and diameter instability. We developed a mechanism-guided extrusion toolkit to stabilize polylactic acid (PLA) filaments containing human demineralized bone matrix (DBM) or cortical granulate (CG) up to 70 wt%. PLA was ground, dried, silicone pre-coated, and compounded with DBM or CG (25/40/70 wt%) using starve-fed extrusion, sequential extrusion, and post-die mixing to maintain stable diameters. FFF produced disks and tubes. MSC adhesion was assessed by SEM. qPCR (control vs. osteogenic medium) quantified RUNX2, ALP, BGLAP, COL1A, VEGF, IL-6, MAPK8. Tubes underwent three-point bending. The toolkit yielded printable, dimensionally stable filaments at 25–70 wt% with uniform dispersion and surface-exposed filler. Both composites increased early mesenchymal stromal cells (MSC) adhesion versus PLA. RUNX2 was increased on DBM40 versus PLA. VEGF was elevated on CG25 (DBM40 trend). Under osteogenic medium, IL-6 and MAPK8 were generally reduced. Mechanics were loading-dependent: CG25 exceeded CG70 and DBM25, while DBM40/70 recovered stiffness versus DBM25. A mechanism-guided extrusion toolkit enables high-loading PLA–DBM/CG filaments with excellent printability and material-specific biological and mechanical advantages over PLA. Full article

The non-albicans Candida species Candida tropicalis is an opportunistic fungal pathogen that forms a robust gel-like biofilm on polymeric prosthetic materials. These biofilms are embedded in an extracellular polymeric substance that retains large amounts of water, resulting in a hydrogel-like matrix that protects fungal cells, increases antifungal resistance, and contributes to the biofouling of these prosthetic materials. Biofouling is the unwanted colonization and accumulation of microbial communities on material surfaces, which alters their function and compromises clinical performance. Clinically, it is significant because it is linked to recurrent urinary tract infections, bloodstream infections, and persistent device-related infections, which often result in therapeutic failure and device malfunction. Polymers such as silicone elastomer, polypropylene, polystyrene, polyurethane, polyethylene, and polyvinyl chloride are widely used in catheters, surgical meshes, implants, and prostheses because of their durability, flexibility, and biocompatibility, yet their surface properties often encourage microbial adhesion and biofilm formation. This review emphasizes that the gel-like biofilm architecture of C. tropicalis underpins its persistence and resistance, while also highlighting promising antifungal strategies being developed to mitigate these infections. Notably, palmitic acid has been shown to disrupt mature biofilms by lowering ergosterol and inducing oxidative stress, whereas C-10 massoia lactone damages the extracellular matrix and suppresses hyphal growth. Drug repurposing approaches, such as combining minocycline with fluconazole, restore susceptibility in resistant isolates and demonstrate synergistic antibiofilm activity. Additionally, biomaterial-based interventions, such as chitosan coatings on silicone surfaces, significantly reduce fungal adhesion and biofilm formation. Together, these findings reflect a translational shift toward integrating natural products, repurposed drugs, and functionalized biomaterials into antifungal development. Understanding biofouling and these emerging strategies is crucial for developing effective control measures against C. tropicalis biofilms and for guiding the design of infection-resistant prosthetic devices. Full article

The interface between biomaterials and biological systems is crucial for medical implants and tissue engineering. Surface modifications are a key strategy for controlling interactions. Synthetic glycopolymers offer a versatile toolbox, mimicking the structure and function of natural glycoconjugates like mucins. This review highlights the significance of glycopolymers for targeted surface modifications of established biomaterials, such as silicones and poly(meth)acrylates. Controlled polymerization techniques, like the reversible-addition-fragmentation chain-transfer (RAFT) polymerization, enable the synthesis of well-defined glycopolymer architectures. Glycopolymeric surface functionalization creates tailored interfaces for different biological responses, from preventing protein and cell adhesion to promoting specific cell-type binding. The focus lies on using single, well-characterized polymeric base materials and tuning their surface properties through glycopolymer coatings to achieve various and specific functions. This approach opens new dimensions in the development of advanced biomaterials for applications like contact lenses, drug delivery systems, and biosensors and also possesses potential regulatory advantages by leveraging the safety profiles of existing materials. Full article

Laser powder bed fusion has attracted increasing attention for the production of metallic substrates intended for surface functionalization by advanced physical vapor deposition coatings. This study investigates the influence of the substrate manufacturing route on the performance of titanium–aluminum–silicon nitride-coated AISI 316L stainless steel, with particular emphasis on substrates produced by laser powder bed fusion. Conventionally manufactured and additively manufactured AISI 316L substrates were coated with a titanium–aluminum–silicon nitride layer using high-power impulse magnetron sputtering. The substrates were characterized by tensile testing and microhardness measurements, while coating thickness and uniformity were evaluated using the crater ball method. The mechanical integrity of the coating–substrate system was assessed by progressive load scratch testing. The additively manufactured substrate exhibited a significantly higher yield strength (411 MPa) compared to the conventionally manufactured material (257 MPa), together with increased microhardness. The titanium–aluminum–silicon nitride coating showed a uniform thickness of 4.47 µm and a well-defined coating–substrate interface. Scratch tests revealed a delayed onset of coating damage on additively manufactured substrates, with the transition to severe adhesive failure occurring at higher normal loads compared to the conventionally manufactured substrate. These results demonstrate that AISI 316L stainless steel produced by laser powder bed fusion provides a mechanically robust substrate for titanium–aluminum–silicon nitride coatings deposited by high-power impulse magnetron sputtering, with favorable coating response under progressive loading conditions. Full article

The main purpose of this study was to investigate the effects of 10, 20, and 40 wt% micron-sized particles (aluminum nitride, aluminum oxide, silicon nitride, and silicon oxide) on the thermal performance of an epoxy resin used in microelectronic devices. Specimens were produced via a solution mixing technique followed by molding and curing. Although there were slight differences between the particle types used, various thermal analyses revealed that increasing the amount of all particle types significantly improved the thermal performance of the epoxy resin. The property that influences the thermal performance of microelectronic devices the most is thermal conductivity (λ). Heat produced during operation should be released via heat diffusion, which requires a certain level of λ. In this study, the use of a 40 wt% particle content increased the thermal conductivity (λ) by more than 3 times compared to neat epoxy (0.15 W/m·K). Another significant problem during the operation of these devices is the formation of “thermal strain mismatch” due to the different thermal expansion coefficients (α) of the materials used in the device that might lead to a loss of dimensional stability and malfunctioning. In this study, a particle content of 40 wt% decreased the thermal expansion coefficient of epoxy (49 × 10⁻⁶/K) down to 28 × 10⁻⁶/K, a decrease of −43%. Thermal performance also depends on the Glass Transition Temperature (T_g) values. In this study, a particle content of 40 wt% increased the T_g from 51 °C (neat epoxy) to 68 °C, an increase of 17 °C, and increased the Thermal Degradation Temperature (T_d) from 324 °C (neat epoxy) to 356 °C, an increase of 32 °C. Moreover, it was also revealed that there was no decrease in the lap shear adhesion strength of the epoxy resin after incorporation of any of the particle types. Additionally, the particles also increased the mechanical rigidity of the epoxy in terms of Storage Modulus at 25 °C and 50 °C. Full article