Micro

This study presents the development of a modified polyimide (MPI) with low dielectric properties and low-temperature curing capability for high-frequency flexible printed circuit boards (FPCBs). MPI was cured using dicumyl peroxide (DCP) at 80–140 °C through a radical process optimized via DSC analysis, while Fourier-transform infrared (FT-IR) confirmed the elimination of C=C bonds and the formation of imide structures. The MPI film exhibited low dielectric constants (D_k) of 1.759 at 20 GHz and 1.734 at 28 GHz, with ultra-low dissipation factors (D_f) of 0.00165 and 0.00157. High-frequency S-parameter evaluations showed an excellent performance, with S11 of −32.92 dB and S21 of approximately −1 dB. Mechanical reliability tests demonstrated a strong peel strength of 0.8–1.2 kgf/mm (IPC TM-650 2.4.8 standard) and stable electrical resistance during bending to ~6 mm radius, with full recovery after severe deformation. These results highlight MPI’s potential as a high-performance dielectric material for next-generation FPCBs, combining superior electrical performance, mechanical flexibility, and compatibility with low-temperature processing. Full article

Microneedles (MNs) have emerged as a promising tool for pain-free drug delivery, offering an alternative to traditional syringe-based methods. Among various types of MNs, dissolving microneedles fabricated from hyaluronic acid (HA) have gained attention due to their biocompatibility and ability to deliver drugs with minimal discomfort. However, conventional HA MN fabrication techniques often limit needle lengths to a few hundred micrometers, which is insufficient for deeper drug penetration. This study introduces a novel fabrication method using bidirectional drawing lithography to extend the length of HA-based MNs. By adjusting the viscosity of HA solutions and employing a controlled pulling process, we demonstrate the feasibility of producing MNs with lengths ranging from millimeters to micrometers. An average height of 15 mm and tip diameters of approximately 80 μm were successfully produced. This advancement enhances the potential of HA MNs for transdermal drug delivery and interstitial fluid sampling. Full article

The heat generation characteristics of magnetic nanoparticles (NPs) induced by an alternating magnetic field (AMF) while simultaneously exposed to a DC magnetic field are crucial for the clinical application of magnetic fluid hyperthermia integrated with magnetic particle imaging. In this study, we investigated the dependence of the specific absorption rate (SAR) of magnetite and cobalt (Co) ferrite NP suspensions on a static transverse DC magnetic field under an applied AMF. The results showed that the SAR of Co ferrite NPs remained unaffected by the DC magnetic field, whereas that of magnetite NPs gradually decreased as the DC magnetic field increased. Furthermore, the SAR of magnetite NPs dispersed in high-viscosity solvents was somewhat lower than that of particles dispersed in water, while the SAR of Co ferrite NPs was significantly reduced. These findings can be explained by differences in the Néel relaxation time, which arise from variations in magnetic anisotropy. Full article

The objective of this research was to fine-tune the surface properties of printed ink layers by incorporating TiO₂ and ZnO nanoparticles into conventional flexographic ink. This modification aimed to improve print quality while simultaneously providing protection against counterfeiting. The presence of nanoparticles in the inks was indirectly detected through FTIR-ATR spectroscopy, which revealed changes in the fingerprint region of the ink spectrum when nanoparticles were added. This alteration enhanced the anti-counterfeiting potential of a produced print. The colorimetric measurements indicated that the addition of nanoparticles did not significantly affect the colorimetric properties of the print, since the maximal calculated ΔE_ab value was 2.83. However, the nanoparticles notably improved the ink coverage on printed line elements and allowed for the printing of elements without the characteristic outline associated with flexographic printing. The best results in terms of line definition and coverage were achieved with the addition of 2% rutile TiO₂ and 1% ZnO to the ink: the measured line segment area covered in ink was 28.5% larger than the same area printed using unmodified ink. This improvement in print quality was attributed to the modified surface free energy (SFE) of the inks, which also influenced the adhesion parameters between the printed layer and the printing substrate. The lowest total SFE was calculated for the ink without added nanoparticles (40.31 mJ/m²), and the highest for the ink with the addition of 2% rutile TiO₂ (48.33 mJ/m²). The work of adhesion increased after adding the nanoparticles to the ink, thereby improving the adhesion. The highest work of adhesion (79.36 mJ/m²) was calculated for the ink with 2% rutile TiO₂. Interfacial tension was low and close to zero for all printed ink layers, and the lowest value was achieved for the ink without added nanoparticles (1.47 mJ/m²). The findings of this research demonstrated that fine-tuning the properties of flexographic inks using nanoparticles can yield several benefits in terms of optimizing the quality of and providing counterfeit protection for specific printed motifs. Full article

Thermal energy storage offers a viable solution for managing intermediate energy availability challenges. Phase change materials (PCMs) have been extensively studied for their capacity to store thermal energy when available and release it when needed, maintaining a narrow temperature range. However, effective utilization of PCMs requires its proper encapsulation in most applications. In this study, microcapsules containing Rubitherm^®(RT) 21 PCM (Tpeak = 21 °C, ΔH = 140 kJ/kg), which is suitable for buildings, were synthesized using a suspension polymerization technique at different operating temperatures (45–75 °C). Two different water-insoluble thermal initiators were evaluated: 2,2-Azobis (2,4-dimethyl valeronitrile) (Azo-65) and benzoyl peroxide (BPO). The prepared microcapsules were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), particle size distribution (PSD), scanning electron microscope (SEM), and optical microscopy (OM). Additionally, the microcapsules were subjected to multiple melting and freezing cycles to assess their thermal reliability and performance stability. DSC results revealed that the microcapsules using BPO exhibited a latent heat of melting comparable to those produced with Azo-65 at an operating temperature of 75 °C. However, the onset crystallization temperature for the BPO-encapsulated PCMs was approximately 2 °C lower than that of the Azo-65-encapsulated PCMs. The greatest latent heat of melting, 107.76 J/g, was exhibited by microcapsules produced at 45 °C, representing a PCM content of 82 wt. %. On the other hand, microcapsules synthesized at 55 °C and 75 °C showed latent heats of 96.02 J/g and 95.66 J/g, respectively. The degree of supercooling for PCM microcapsules was reduced by decreasing the polymerization temperature, with the lowest supercooling observed for microcapsules synthesized at 45 °C. All microcapsules exhibited a monodisperse and narrow PSD of ~10 µm, indicating uniformity in microcapsule size and demonstrating that temperature variations had no significant impact on the particle size distribution. Future research should focus on low-temperature polymerization with extended polymerization times. Full article

The increasing global demand for food caused by a growing world population has resulted in environmental problems, such as the destruction of ecologically significant biomes and pollution of ecosystems. At the same time, the intensification of crop production in modern agriculture has led to the extensive use of synthetic fertilizers to achieve higher yields. Although chemical fertilizers provide essential nutrients and accelerate crop growth, they also pose significant health and environmental risks, including pollution of groundwater and other bodies of water such as rivers and lakes. Soils that have been destabilized by indiscriminate clearing of vegetation undergo a desertification process that has profound effects on microbial ecological succession, impacting biogeochemical cycling and thus the foundation of the ecosystem. Tropical countries have positive aspects that can be utilized to their advantage, such as warmer climates, leading to increased primary productivity and, as a result, greater biodiversity. As an eco-friendly, cost-effective, and easy-to-apply alternative, biofertilizers have emerged as a solution to this issue. Biofertilizers consist of a diverse group of microorganisms that is able to promote plant growth and enhance soil health, even under challenging abiotic stress conditions. They can include plant growth-promoting rhizobacteria, arbuscular mycorrhizal fungi, and other beneficial microbial consortia. Bioremediators, on the other hand, are microorganisms that can reduce soil and water pollution or otherwise improve impacted environments. So, the use of microbial biotechnology relies on understanding the relationships among microorganisms and their environments, and, inversely, how abiotic factors influence microbial activity. The recent introduction of genetically modified microorganisms into the gamut of biofertilizers and bioremediators requires further studies to assess potential adverse effects in various ecosystems. This article reviews and discusses these two soil correcting/improving processes with the aim of stimulating their use in developing tropical countries. Full article

Microplastics (MPs) and nanoplastics (NPs) have emerged as persistent environmental pollutants, posing significant ecological and human health risks. Their widespread presence in aquatic, terrestrial, and atmospheric ecosystems necessitates effective removal strategies. Traditional removal methods, including filtration, coagulation, and sedimentation, have demonstrated efficacy for larger MPs but struggle with nanoscale plastics. Advanced techniques, such as adsorption, membrane filtration, photocatalysis, and electrochemical methods, have shown promising results, yet challenges remain in scalability, cost-effectiveness, and environmental impact. Emerging approaches, including functionalized magnetic nanoparticles, AI-driven detection, and laser-based remediation, present innovative solutions for tackling MP and NP contamination. This review provides a comprehensive analysis of current and emerging strategies, evaluating their efficiency, limitations, and future prospects. By identifying key research gaps, this study aims to guide advancements in sustainable and scalable microplastic removal technologies, essential for mitigating their environmental and health implications. Full article

This paper presents the design and fabrication of flexible and gel-less electrodes using carboxylic acid-functionalized single-walled carbon nanotubes (SWCNT-COOHs) and polydimethylsiloxane (PDMS) at thirteen different concentrations. The dispersion was attained by magnetic stirring and sonication using isopropyl alcohol (IPA). Physical characterizations like Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR) were performed. The electrodes were fabricated using molds. The percolation threshold was achieved at 4 wt%. The ECG results were compared with conventional ECG electrodes and 3.5 wt% displayed the best results. Also, after using the electrodes for 5 days, the ECG signals did not degrade and no skin allergies were observed. The fabricated electrodes are suitable for long-term and continuous ECG monitoring, facilitated with the help of an Internet of Things (IoT) tracking system. The data can then be transmitted to the medical expert and loaded onto the cloud server for analysis. Full article

Hydrogen peroxide (H₂O₂) detection in both liquid and gas phases has garnered significant attention due to its importance in various biological and industrial processes. Monitoring H₂O₂ levels is essential for understanding its effects on biology, industry, and the environment. Significant advancements in the physical dimensions and performance of biosensors for H₂O₂ detection have been made, mainly through the integration of fluorescence techniques and nanotechnology. These advancements have resulted in more sensitive, selective, and versatile detection systems, enhancing our ability to monitor H₂O₂ in both liquid and gas phases effectively. However, limited comprehensive reviews exist on the detection of vaporized H₂O₂, which is used in disinfection and the production of explosive agents, making its detection vital. This review provides an overview of recent progress in nanostructured fluorescence sensors for H₂O₂ detection, covering both liquid and gas phases. It examines various fluorescence-based detection methods and focuses on emerging nanomaterials for sensor development. Additionally, it discusses the dual applications of H₂O₂ detection in biomedical and non-biomedical fields, offering insights into the current state of the field and future directions. Finally, the challenges and perspectives for developing novel nanostructured fluorescence sensors are presented to guide future research in this rapidly evolving area. Full article

Carbon dots (CDots) are classically defined as small carbon nanoparticles with effective surface passivation, which, in the classical synthesis, has been accomplished by surface organic functionalization. CDot-like nanostructures could also be produced by the thermal carbonization processing of selected organic precursors, in which the non-molecular nanocarbons resulting from the carbonization are embedded in the remaining organic species, which may provide the passivation function for the nanocarbons. In this work, a mixture of oligomeric polyethylenimine and citric acid in the solid state was used for efficient thermal carbonization processing with microwave irradiation under various conditions to produce dot samples with different nanocarbon content. The samples were characterized in terms of their structural and morphological features regarding their similarity or equivalency to those of the classical CDots, along with their significant divergences. Also evaluated were their optical spectroscopic properties and their photoinduced antimicrobial activity against selected bacterial species. The advantages and disadvantages of the thermal carbonization processing method and the resulting dot samples with various features and properties mimicking those of classically synthesized CDots are discussed. Full article

The spray pyrolysis deposition of nanostructured Pb_1−xSn_xSe alloy films, x = 0.0 to 1.0, from as-prepared Pb_1−xSn_xSe alloy colloids as the starting solution is reported. The colloidal dispersions were prepared by dissolving selenium in an amine–thiol mixture, reacted with the Sn and Pb precursors in propylene glycol, and subsequently sprayed onto glass substrates at 300 °C. Structural characterization indicated the formation of the alloyed rock-salt cubic phase for 0.0 ≤ x ≤ 0.75, oxidized Pb and Se phases produced during the deposition, and only orthorhombic SnSe for x = 1.0 with Se and SnSe₂ as impurities. Nanocrystalline films ranging from 16 to 16.5 nm in size were obtained. The films displayed a shift in their optical structure and a non-monotonic variation in the band gap energy, first a decrease, reaching the minimum at x = 0.30 and a further increase in the Sn content. The decrease in the optical band gap resembles that of a topological insulator behavior. The morphology of the alloyed films confirmed the large nanocrystal formation by self-assembly processes in both the PbSe and SnSe phases and segregated PbSnSe platelets for x ≥ 0.30. Seebeck coefficient revealed that a typical semiconductor behavior dominated by bipolar transport, and p-type conductivity, but only for x = 0.0 n-type conductivity was exhibited. The maximal Seebeck coefficient magnitude behaved similarly to the band gap energy, evidencing the influence of energy band structure and the topological character. Full article

Polyvinylidene fluoride (PVDF) is a multifunctional polymer renowned for its unique electrical, mechanical, and piezoelectric properties, making it an attractive candidate for various applications. Although the spin-coating method has been the conventional method for fabricating PVDF thin films, this work is the first to apply the dip-coating technique with humidity control, which is a largely unexplored method in the literature on PVDF thin films. This novel approach offers great prospects for improved control and performance adjustments, as well as expanding the range of film deposition procedures. Here, we examine the phase composition of PVDF thin films; adjust different parameters to optimize the electroactive phases fraction, especially the Beta phase; and examine how relative humidity affects the properties of the film. Moreover, we test the impact of different nanoparticles’ addition on the phases fraction and characteristics of the film. Furthermore, we analyze the topography of the resultant films using several approaches, providing fresh insights into their structural features. Full article

The cosmetic market is constantly evolving and ever-changing, particularly with the introduction and incorporation of nanotechnology-based processes into cosmetics for the production of unique formulations with both aesthetic and therapeutic benefits. There is no doubt that nanotechnology is an emerging technology for cosmetic formulations. Among the numerous cosmetic items, incorporating nanomaterials has provided a greater scope and is commonly utilized in facial masks, hair products, antiaging creams, sunscreen creams, and lipsticks. In cosmetics, nanosized materials, including lipid crystals, liposomes, lipid NPs, inorganic nanocarriers, polymer nanocarriers, solid lipid nanocarriers (SLNs), nanostructured lipid carriers (NLCs), nanofibers, nanocrystals, and nanoemulsions, have become common ingredients. The implementation of nanotechnology in the formulation of face masks will improve its efficacy. Nanotechnology enhances the penetration of active ingredients used in the preparation of face masks, such as peel-off masks and sheet masks, which results in better effects. The emphasis of this review is mainly on the formulation of cosmetic face masks, in which the impact of nanotechnology has been demonstrated to improve the product performance on the skin. Full article

Microscale systems have been underexplored in contemporary regenerative therapies developed to treat vision loss. The pairing of in vitro cell systems with optical fluorescent imaging provides unique opportunities to examine the infiltration of donor stem cells needed for successful transplantation therapies. A parallel eye device was developed to provide electric field (EF) stimulation to guide the migration of cells within 3D eye facsimiles synthesized from different ocular biomaterials. Cell infiltration within facsimiles was rapidly resolved using confocal microscopy to eliminate dependence on the cryostat sectioning commonly used for cell study. Moreover, EF stimulated galvanotaxis of donor cells within different depths of eye facsimiles. Optical imaging provided rapid resolution of z-stack images at physiologically appropriate depths below 500 microns. This study demonstrates that paired microscale–optical systems can be developed to elucidate understudied transplantation processes and improve future outcomes in patients. Full article

Escherichia coli (E. coli) and Agrobacterium tumefaciens (A. tumefaciens) are bacterial species commonly found in the environment, and they can do much harm to humans, animals and plants. As a result, it is necessary to find an accurate, rapid, simple method to detect the concentrations of them, and polymerase chain reaction (PCR) is one of the most suitable candidates. In this study, a gold nanoparticles (GNPs) enhanced polymerase chain reaction was developed, to simultaneously target the specific genes, 16S rDNA of E. coli and Tms1 of A. tumefaciens. PCR amplification times (CT values) of E. coli and A. tumefaciens were seen to be lowered significantly by the incorporation of GNPs. The fluorescence intensities in quantitative PCR amplifications of both E. coli and A. tumefaciens reached the maximum after around 40 cycles, and the PCR yield (maximum fluorescence intensity) was proportional to the maximum absorbance at 495 nm in the corresponding UV-vis spectra. GNPs were found to enhance the PCR yield of both E. coli and A. tumefaciens, and smaller sized GNPs (average 13 nm) showed a better enhancement effect compared to larger sized GNPs (average 30 nm). Conventional PCR showed that both E. coli and A. tumefaciens could be detected together with limit of detection of 10 CFU/mL for each bacterium, using GNPs of 13 nm. The results of this study could lead to improvement of multiplex PCR that can detect different bacteria species simultaneously. Full article

Any application of nanoparticles is influenced by the unavoidable tendency of these particles to agglomerate. As a result, one obtains a more or less broad distribution of agglomerate sizes. This may influence the properties significantly. Looking at agglomeration processes, one has to distinguish two different phenomena: the generally discussed problem, where each particle has the chance to combine with any other particle, or the case, where an agglomeration is possible only with direct neighbors. The latter case, which is the subject of this study, is observed when the particles are stored in a box. In contrast to conventional analyses, the calculations for this paper are based on Markov chain Monte Carlo calculations. This paper describes the formation and development of these agglomerates and the resulting distributions. For an improved depiction of the results, a new quantity derived from entropy, the ‘integral entropy’, was developed. This quantity allows efficient visualization of the development of the agglomerates as a function of the iteration steps resulting from these calculations; additionally, applying the integral reduces the statistical scattering of the results. Furthermore, different mechanisms and interaction parameters were assumed and compared. The results were analyzed to show progress that depends on the number of iteration steps. An important result of these calculations is the distribution of agglomerate sizes and the number of agglomerates as a function of the number of iterations. The calculations are based on different assumptions on the agglomeration and arrangements of the particles. Full article

In recent years, various types of sensors have been developed at both millimeter (mm) and micrometer (µm) scales for numerous biomedical applications. Each design has its own advantages and limitations. This study compares the electrical characteristics and sensitivity of millimeter- and micrometer-scale sensors, emphasizing the superior performance of millimeter-scale designs for detecting type-2 diabetes. Elevated glucose levels in type-2 diabetes alter the complex permittivity of red blood cells (RBCs), affecting their rheological and electrical properties, such as viscosity, volume, relative permittivity, dielectric loss, and AC conductivity. These alterations may manifest as a unique bio-impedance signature, offering a diagnostic topology for diabetes. In view of this, various concentrations (ranging from 10% to 100%) of 400 µL of normal and diabetic RBCs suspended in phosphate-buffered saline (PBS) solution are examined to record the changes in bio-impedance signatures across a spectrum of frequencies, ranging from 1 MHz to 10 MHz. In this study, simulations are performed using the finite element method (FEM) with COMSOL Multiphysics^® to analyze the electrical behavior of the sensors at both millimeter (mm) and micrometer (µm) scales. These simulations provide valuable insights into the performance parameters of the sensors, aiding in the selection of the most effective design by using this topology. Full article

Quercetin, a flavonoid, has well-proven cytotoxicity potential, but its therapeutic efficacy is hampered by hydrophobicity, stability issues, and lower bioavailability. The present research aims to address these issues and formulation barriers by formulating a quercetin-loaded micellar nanogel. Quercetin was encapsulated in PF 68 micelles to enhance its solubility, loading, and stability to better its therapeutic potential. The nanogel was further characterized regarding for pH, spreadability, and in vitro cytotoxicity against human breast cancer cells (MCF-7). The resulting micelles exhibited a particle size of 180.26 ± 2.4 nm, surface charge of −13.5 mV, entrapment efficiency of 78.4 ± 1.2%, and in vitro release of 96.11 ± 0.75% up to 8 h. This in vitro cytotoxicity study on MCF-7 cell lines reveals the improved TGI and GI 50 values of micellar nanogel formulation compared to quercetin. The overall study results demonstrated that the developed micellar nanogel system might serve as a promising nanocarrier to enhance the cytotoxic potential of quercetin in cancer therapy. Full article

This work determined the resistance of paint formulations containing TiO₂ particles to fungal growth. Siloxane, acrylic and silicone paints were placed outdoors, and the fungal species growing thereon were recorded after 3, 6 and 9 months. In addition, three paint types containing TiO₂ with/without biocide were inoculated with fungal spores and irradiated using UV. Acrylic paints were also doped with different metals and were inoculated and incubated under fluorescent light. Following outdoor incubation, the silicone paint was the least colonised by different fungal species. The species most recovered from the surfaces were Aspergillus spp. and Penicillium spp. Following UV irradiation on different paints containing biocide and/or a photocatalyst, no fungal growth was demonstrated on some of the paint combinations. When the paint samples were doped with different metals and incubated using light, the sample most efficient at preventing fungal growth contained lanthanum (0.004%). The paint samples containing praseodymium (light:1.72) facilitated the densest fungal colonies. Most of the surfaces demonstrated heterogeneous coverage by the fungi. The most clustered fungal colonisation was on surfaces incubated in the light. This work demonstrated that fungal colonisation on paints changed over time and that the antimicrobial efficacy of TiO₂ was affected by the chemical composition, biocide and doping of the paint. Full article