Surface modification of polymers is essential for improving adhesion, coating performance, and wettability in various industrial and environmental applications. In this study, uniformly cut samples of common plastics such as polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and high-density polyethylene (HDPE) were exposed to a low-cost atmospheric cold plasma (ACP) system using a zero-voltage switching (ZVS). The plasma system operated at an output of 10–20 kV, using argon (Ar), nitrogen (N₂), and oxygen (O₂) as working gases under atmospheric conditions. Samples were treated for 5 and 10 min of exposure. Surface modifications were analyzed using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), and contact angle measurements (CAM). A pronounced roughness enhancement was found in PP and HDPE. Moderate changes were seen in PET and PVC, while PS had a minimal response. FTIR confirmed the creation of oxygen-containing functional groups (–OH, C= O), enhancing surface polarity. The contact angle of PP decreased from 108° to 47°, while HDPE decreased from 80° to 62°, showing that improvements in wettability arise from the combined effects of chemical functionalization and increased surface roughness. These findings demonstrate that the low-cost ACP system effectively tailors polymer surface chemistry and morphology, providing a scalable and eco-friendly approach for adhesion, coating, and sustainable polymer processing applications.

Plastic pollution in aquatic environments has become a major global concern, affecting both marine ecosystems and human health. This study presents the design and experimental evaluation of a portable 405 nm portable laser diode-based Mie lidar system for detecting and distinguishing submerged plastics using elastic backscatter signals. The system was configured in a monostatic arrangement integrating a 405 nm laser diode (pulse width: 12.4 ns, repetition frequency: 552 kHz, peak power: 68.18 mW) and a refracting telescope (75 mm aperture, 1.15 mrad FOV) coupled to a Hamamatsu R6350 photomultiplier tube (PMT) through a 405 nm bandpass filter (>90% transmission). The photon-counting detection was performed using an FPGA-based Trimatiz Photon Tracker, which has a temporal resolution of 5 ns. Measurements were conducted under controlled laboratory conditions with water background subtraction to isolate the scattering contribution of three common marine plastics: polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET). Result revealed distinct backscatter profiles, with PS producing the strongest signal, followed by PET and PP, consistent with differences in refractive index and surface reflectivity. The findings demonstrate the potential of a compact Mie lidar as a simple, low-power, and cost-effective tool for identifying and monitoring plastics in aquatic environments, paving the way for future in-situ ocean applications.

This study explores the relationship between nutrient concentration (NC) and epidermal thickness (d) of the leaves of hydroponically grown Brassica rapa and its attenuation coefficients (m) using portable Time-Domain Optical Coherence Tomography (TD-OCT), which is a non-invasive imaging technique that uses low-coherence interferometry to generate axial scans of plants’ leaves by measuring the time delay and intensity of backscattered light. The portable TD-OCT system in this study has an axial and lateral resolution of 7 m and 3 m, respectively, a scanning depth of 12 mm, and a 1310 nm Super Luminescent Diode (SLD). Several studies suggest that the differences in d and m are related to nutritional, physiological, and anatomical status. The study used the Kratky method, a simple non-circulating hydroponic system, to cultivate Brassica rapa with varying NC (25%, 50%, 75%, 100% (control), and 125%). Each treatment group used two plants. The TD-OCT sample probe was placed on a fixed holder and was oriented vertically so that light was directed downward onto the leaf’s surface to obtain the depth profile (A-scan). The distance between the probe and the leaf was adjusted to obtain the optimum interference signal. Five averaged A-scans were obtained per leaf on the 7th, 18th, and 21st days post nutrient exposure. The logarithm of the averaged A-scan is linearly fitted to extract m. The results showed a positive correlation between NC and m, which suggests that plants produce more chlorophyll and develop denser cells and increase m. There was no correlation obtained between NC and d. The study demonstrates the potential of TD-OCT as a non-destructive tool for assessing plant health and monitoring growth dynamics in hydroponic systems and m as a sensitive indicator of plant health as compared to d. The continued exploration of TD-OCT applications in agriculture can contribute to improving crop management strategies and promoting sustainable food production practices.

Background/Objectives: Dental biofilm formation on prosthetic materials contributes to oral diseases and material degradation. This pilot study evaluated the feasibility of combining time-domain optical coherence tomography (TD-OCT) and non-contact atomic force microscopy (NC-AFM) to characterize biofilm-associated optical and surface changes in dental prosthesis materials following antiseptic treatment. Methods: Acrylic resin, composite resin, and stainless-steel specimens were inoculated with Streptococcus mutans biofilms and exposed to water, Orahex, and Watsons mouthwash. TD-OCT was used to obtain extinction coefficient (EC) and optical thickness measurements, while NC-AFM was performed on Orahex-treated specimens to assess nanoscale surface morphology. EC distributions were analyzed descriptively from valid TD-OCT A-scans. Results: Within the examined specimens, EC distributions varied following biofilm formation and antiseptic treatment, with material-dependent responses. Composite resin exhibited the clearest reduction in EC following Watsons treatment, whereas acrylic resin and stainless-steel specimens showed more variable responses. Physical thickness remained relatively stable, while NC-AFM observations of the Orahex-treated specimens supported the TD-OCT findings by demonstrating corresponding surface morphological changes. Conclusions: This pilot study demonstrates the preliminary feasibility of integrating TD-OCT with NC-AFM for non-destructive evaluation of biofilm-associated optical and surface changes in dental prosthesis materials. The findings are descriptive and exploratory, highlighting the potential of TD-OCT for monitoring prosthetic materials while emphasizing the need for future studies incorporating independent biological replicates and complementary biological validation techniques.