While Polymer Optical Fibers (POFs) are favored for their mechanical resilience, increasing their sensitivity typically requires hazardous chemical etching that damages the fiber surface. To avoid these chemical defects, we propose a physical alternative: a "thermal bandgap modulation" protocol. The core idea was to determine if heat treatment alone could tune the fiber’s surface for better sensitivity, while avoiding the structural damage often caused by chemical methods. We tested Polymethyl Methacrylate (PMMA) fibers across three distinct thermal stages: stress relaxation (100°C), viscoelastic transition (150°C), and the onset of oxidative degradation (200°C). Rather than relying on standard transmission methods, we analyzed the fibers using reflection spectroscopy in the 300–700 nm range. By applying the Kubelka–Munk transformation to this reflection data, we were able to calculate the optical band gap (E_g) and Urbach energy (E_u)—metrics that are rarely used in macroscopic sensor fabrication.

Our results show a clear difference in how the material behaves based on its thermal history. At 100°C, the fiber simply relaxes, keeping its transparency and a stable UV-limit band gap. However, at 200°C, we observed a distinct narrowing of the optical band gap as the absorption edge moved toward the visible spectrum. This shift matched a widening of the Urbach tail, which indicates the formation of carbon-rich clusters and increased structural disorder. We found that this induced disorder is not just damage; it acts as a tunable parameter that is directly linked to a significant rise in sensitivity. By carefully managing the thermodynamic state of the polymer, we present a sustainable, high-precision way to build intrinsic fiber optic sensors.

Introduction:

Biofilms are communities of microorganisms on moist surfaces that are difficult to remove and can repeatedly release microorganisms. This causes significant problems in many areas, such as food technology and medicine as biofilms can cause infections in patients that can be potentially fatal. One approach to preventing biofilm formation on surfaces that has not yet been extensively researched is to irradiate them with visible blue or violet light, both of which are known for their antimicrobial effect on planktonic bacteria.

Methods:

Various bacterial suspensions (Bacillus subtilis, Pseudomonas stutzeri, Streptococcus cristatus and Pseudomonas syringae) were placed in 24-well MTPs (microtiter plates) and irradiated with violet or blue light for up to 6 days. During this time, they were shaken at room temperature at a frequency of 100 rpm. The irradiation intensities were 0 mW/cm², 10 mW/cm², or 20 mW/cm². After each day, the bacterial suspension was aspirated and the biofilm at the bottom of the well was assessed by absorption measurement and microscopy imaging.

Results:

In almost all experiments, thin biofilms were found on the well bottoms after 24 hours, even on the irradiated microtiter plates. In general, however, the level of absorption or biofilm formation was lower on the irradiated MTPs than on the non-irradiated ones. For Bacillus subtilis, irradiation prevented biofilm formation during the observation period. Surprisingly, in most experiments, blue light had a stronger effect than violet light, which does not correspond to previous reports regarding their effect on planktonic bacteria.

Conclusion:

Violet and blue light have a positive effect on suppressing the formation of new biofilm, but the applied maximum irradiance of 20 mW/cm² was not able to prevent the formation of new biofilms. Further investigations with higher irradiance levels are necessary to determine whether it is possible to inhibit the formation of new biofilms altogether.

This paper presents the modeling and simulation of a multilayer surface acoustic wave (SAW) resonator designed to operate at a center frequency of 30 GHz. The proposed structure consists of a layered stack of silicon (Si), aluminum nitride (AlN), silicon dioxide (SiO₂), and lithium niobate (LiNbO₃), with gold (Au) interdigitated transducer (IDT) electrodes placed on the top surface. This multilayer configuration enhances surface wave confinement and piezoelectric efficiency while maintaining compatibility with silicon-based integration platforms. A two-dimensional finite element model is developed in COMSOL Multiphysics, incorporating the elastic and dielectric properties of each material. The IDT electrodes are modeled as terminals, with a 1 V excitation applied to one electrode and the other grounded. A frequency-domain sweep is performed over the range of 28 GHz to 32 GHz to extract key performance indicators such as the input impedance (Zin) and the S11 reflection coefficient. Simulation results confirm the presence of a Rayleigh-type SAW, tightly confined near the surface of the LiNbO₃ layer. The primary resonance is observed at 29.57 GHz, which aligns well with the designed acoustic wavelength. This work demonstrates the effectiveness of multilayer SAW resonators for future MEMS, RF filtering, and acoustic sensing applications at the nanoscale, with high frequency selectivity and integration potential.

Introduction: Breast cancer remains a major global health challenge, motivating the development of multifunctional nanoplatforms that unify diagnosis and therapy. This study presents a novel dendrimer-functionalized magnetite nanocarrier (MAGSiAG₁) and its ibuprofen-loaded derivative (IBU@MAGSiAG₁) designed for synergistic chemotherapy, magnetic hyperthermia, and MRI-guided theranostics.

Methods: Magnetite nanoparticles are synthesized and sequentially coated with SiO₂, APTES, cyanuric chloride, and poly(amidoamine) (PAMAM) G₁ dendrimer. Ibuprofen was loaded through sonication-assisted adsorption. Structural and physicochemical characterization was performed using different spectroscopic and imaging- and potential-based techniques, like FTIR, XRD, TGA, DLS, zeta potential, VSM, and SEM/TEM. pH-responsive drug release was evaluated across physiological and tumor-mimicking conditions. T2 relaxation and hence r2 relaxivity were quantified in MRI phantoms, and hyperthermia treatment was assessed under alternating magnetic field conditions (200 kHz, 100–150 Oe). In vitro cytotoxicity and live/dead imaging were conducted on MCF-7 breast cancer and EA. hy926 endothelial cells.

Results: IBU@MAGSiAG₁ featured stable spherical nanocarriers (~70 nm, −39 mV) with high ibuprofen loading (>90%). Drug release was accelerated at acidic pH (5.0–6.5) mimicking a cancer microenvironment, while it was suppressed at physiological pH 7.4. The nanocarriers retained superparamagnetic (35–40 emu/g) features and achieved therapeutic hyperthermia temperatures (~45 °C) at 150 Oe. High relaxivity (358.9 ± 5 mM⁻¹ s⁻¹ for MAGSiAG₁; 335.0 ± 49.8 mM⁻¹ s⁻¹ for IBU@MAGSiAG₁) confirmed strong MRI contrast enhancement. MCF-7 viability decreased to ~60% at 400 µg/mL, while EA.hy926 cells remained highly viable at ≤300 µg/mL, indicating selective therapeutic action.

Conclusions: This multifunctional dendrimer nanocarrier integrated MRI contrast enhancement, magnetic hyperthermia, and pH-triggered ibuprofen release into a single platform, enabling targeted ablation of breast cancer cells with acceptable biocompatibility. These results highlight its strong potential for personalized and image-guided cancer theranostics.