Eduardo R. Magdaluyo

Silver nanoparticles (AgNPs) are increasingly explored as alternatives to conventional antibiotics in wound care due to their broad-spectrum antimicrobial activity. This study evaluates the antibacterial performance of α-lipoic acid-functionalized silver nanoparticles (AgNPs-LA) using an integrated experimental-computational approach combining molecular dynamics simulations and experimental validation. AgNPs-LA were synthesized via a controlled hydrothermal method employing biogenic reduction of silver ions to minimize cytotoxicity. Structural and compositional analyses confirmed successful surface functionalization with α-lipoic acid and D-glucose. Morphological characterization revealed predominantly spherical nanoparticles with diameters ranging from 37 to 90 nm. Antimicrobial agar disk diffusion assays demonstrated concentration-dependent inhibition of Staphylococcus aureus , Pseudomonas aeruginosa , and Escherichia coli . Specifically, AgNPs-LA at 40 μg/mL produced inhibition zones statistically comparable to gentamicin against S. aureus and P. aeruginosa ( p > 0.05). Molecular dynamics simulations performed under isothermal-isochoric (constant number of particles, volume, and temperature; NVT) canonical ensemble indicated that the disulfide moiety of lipoic acid serves as the primary anchoring group to the silver surface, conferring stability through the formation of a structured hydrophobic surface layer. This interfacial configuration enhances nanoparticle stability and may improve pharmacokinetic clearance, thereby reducing the risk of systemic toxicity. Collectively, these findings highlight the potential of AgNPs-LA as a safe and effective antimicrobial platform for wound management applications.

Mine waste remains a persistent challenge for the minerals industry, posing significant environmental concerns if not properly managed. The 1996 Marcopper Mining Disaster in Marinduque, Philippines, left a legacy of mine tailings that continue to threaten local ecosystems and communities. This study investigates the valorization and stabilization of Marcopper river sediments laden with mine tailings using a combined geopolymerization and cement hydration approach. Hybrid mortar samples were prepared with 7.5%, 15%, 22.5%, and 30% mine tailings by weight, utilizing potassium hydroxide (KOH) as an alkaline activator at concentrations of 1 M and 3 M, combined with Ordinary Portland Cement (OPC). The mechanical properties of the hybrid geopolymer cement mortars were assessed via unconfined compression tests, and their crystalline structure, phase composition, surface morphology, and chemical bonding were also analyzed. Static leaching tests were performed to evaluate heavy metal mobility in the geopolymer matrix. The compression tests yielded strength values ranging from 24.22 MPa to 53.99 MPa, meeting ASTM C150 strength requirements. In addition, leaching tests confirmed the effective encapsulation and immobilization of heavy metals, demonstrating the potential of this method for mitigating the environmental risks associated with mine tailings.

This study evaluated the ballistic performance and failure mechanisms of epoxy-based hybrid laminates reinforced with abaca/UHMWPE and pineapple leaf fiber (PALF)/UHMWPE fabrics fabricated by using vacuum-assisted hand lay-up. Ballistic tests utilized 9 mm full metal jacket (FMJ) rounds (~426 m/s impact velocity) under NIJ Standard Level IIIA conditions (44 mm maximum allowable BFS). This experimental test was complemented by finite element analysis (FEA) incorporating an energy-based bilinear fracture criterion to simulate matrix cracking and fiber pull-out. The results showed that abaca/UHMWPE composites exhibited lower backface signature (BFS) and depth of penetration (DOP) values (~23 mm vs. ~42 mm BFS; ~7 mm vs. ~9 mm DOP) than PALF/UHMWPE counterparts, reflecting superior interfacial adhesion and more ductile failure modes. Accelerated weathering produced matrix microcracking and delamination in both systems, reducing overall ballistic resistance. Scanning electron microscopy confirmed improved fiber–matrix bonding in abaca composites and interfacial voids in PALF laminates. The FEA results reproduced major failure modes, such as delamination, fiber–matrix debonding, and petaling, and identified stress concentration zones that agreed with experimental observations, though the extent of delamination was slightly underpredicted. Overall, the study demonstrated that abaca/UHMWPE hybridcomposites offer enhanced ballistic performance and durability compared with PALF/UHMWPE laminates, supporting their potential as sustainable alternatives for lightweight protective applications.

With the growing demand for reliable, low-impact deployment systems in small satellite missions, this work introduces an antenna deployment mechanism using fiber-reinforced shape memory polymer composites (SMPC). The mechanism utilized thermally activated SMPCs for stowage and release, configured with different glass transition temperatures (T_g), tuned through the addition of poly(ethylene glycol) (PEG-600), for sequential actuation. The deployment mechanism consisted of three SMPC components with varying PEG concentrations: SMPC-P (0 wt%), SMPC-5 (5 wt%), and SMPC-10 (10 wt%). For component design, three bending angle configurations (BAC) of 20°, 30°, and 40° were tested. The samples exhibited the highest fixity ratio (93.58%, 95.76%, and 96.52% for SMPC-P, SMPC-5, and SMPC-10, respectively) when conformed to the 20° BAC. All samples achieved full recovery within 2 min, with PEG-incorporated composites exhibiting more uniform behavior across cycles, while recovery rates varied by material and BAC. Deployment testing confirmed the antenna was released successfully across all BACs. The 20° BAC exhibited the fastest response, completing deployment 24 s and 30 s ahead of the 30° and 40° BACs, respectively. The proposed mechanism exhibits promising potential for integration in future CubeSat missions. However, further testing under simulated space conditions is necessary to comprehensively assess and validate its performance.

Shape memory polymer composites (SMPCs) are an intelligent class of materials capable of self-actuation, offering promising applications in diverse stimuli-responsive material systems. This study developed epoxy-based SMPCs reinforced with carbon–aramid fibers at a 15:85 ratio, with their glass transition temperature (T_g) tailored by incorporating 5 wt.% (SMPC-5) and 10 wt.% (SMPC-10) polyethylene glycol (PEG-600). Dynamic mechanical analysis (DMA) confirmed that PEG addition effectively reduced the T_g from 89.79 °C in the neat composite (SMPC-P) to 70.28 °C in SMPC-5 and 59.34 °C in SMPC-10. Incorporating 5 wt.% PEG enhanced storage and loss moduli, whereas excessive plasticization at 10 wt.% reduced stiffness. Infrared spectroscopy analysis revealed shifts and increased intensities in hydroxyl (OH), aliphatic C-H, and carbonyl (C=O) groups, indicating enhanced intermolecular interactions and bond formation. Tensile testing showed that the carbon–aramid filler significantly improved tensile strength and stiffness, with SMPC-10 achieving the highest tensile strength (233.59 MPa) and SMPC-5 the highest Young’s modulus (14.081 GPa). These results highlight the complementary role of carbon–aramid reinforcement and PEG plasticization in tuning thermomechanical behavior, providing baseline insights for designing SMPCs with tailored actuation and reliable structural performance.

This study focuses on the production of geopolymers incorporating gold mine tailings (GMTs) as the primary aluminosilicate source. Utilizing the Taguchi experimental design, the effects of varying the amounts of sodium silicate (Na₂SiO₃), rice husk ash (RHA), and copper (Cu) on the compressive strength and apparent porosity of the geopolymers were investigated. The results demonstrated that increasing Na₂SiO₃ to 10 wt% and RHA to 20 wt% led to a significant increase in compressive strength, peaking at 3.22 MPa, while elevated Cu levels correlated with decreased strength owing to increased apparent porosity. Analysis of variance highlighted all three parameters as significant signal factors that influenced the compressive strength. However, only the amounts of Cu and RHA showed a significant effect on the material’s apparent porosity, with a maximum of 7.3% increased porosity. Signal-to-noise ratio analysis identified Na₂SiO₃ and Cu as critical factors in minimizing variations of compressive strength. Microstructural analysis via x-ray diffraction confirmed geopolymerization, with the surface morphology displaying grain homogeneity as seen in scanning electron microscope. These findings underscore the potential of GMTs incorporation in geopolymers, emphasizing their sustainability in construction materials and non-load bearing applications, as well as their implications for environmental impact mitigation.

Natural fiber-reinforced polymer composites are gaining attention for their environmental benefits, such as biodegradability and reduced carbon footprint, as well as the potential of the natural fibers to replace or partially substitute synthetic fibers in various applications. However, challenges, such as poor interfacial adhesion and moisture absorption, limit the effectiveness of natural fibers, such as pineapple nonwoven fabric (PNWF) as reinforcement materials in polymer composites. To address these challenges, this study aims to enhance the properties of PNWF through glycidyl methacrylate grafting via radiation-induced graft polymerization. A 22 factorial design was employed to assess the effects of absorbed dosage and monomer concentration on the properties of the grafted PNWF. Infrared spectroscopy and electron microscopy analyses confirmed successful grafting. The grafted PNWF exhibited improved thermal stability and mechanical properties. The resulting composites showed significant enhancements in tensile and flexural strength, specifically, with tensile strength increase ranging from 23.32 to 34.49 MPa and flexural strength from 39.14 to 54.59 MPa. Additionally, the tensile modulus ranged from 0.77 to 1.29 GPa, while the flexural modulus varied from 1.17 to 2.06 GPa. These findings highlight the potential of PNWF grafted with polyglycidyl methacrylate (PNWF-g-PGMA) as an effective reinforcement material for various applications.

Background: Modular external fixations used in the Philippines are manufactured abroad, leading to high costs and limited availability, making them unaffordable for most Filipino patients. The reliability of some external fixators is limited because not all have undergone biomechanical testing. Objective: This study aims to determine the biomechanical stability of locally manufactured modular external fixator clamps (iFIX) versus commercially available fixators (Roger-Anderson) for tibial shaft fractures. Methodology: The biomechanical stability (stiffness, yield, ultimate strength) under loading of the local prototypes compared with the commercially available fixators. Result: No slippage was observed in all rods, pins, and clamps in all groups. No bending occurred in any rods or pins in all groups. There was also no apparent deformation of the internal threading of the pins within the tibial analogs. The commercial fixator group’s ultimate load to failure up was double (110.57% difference) that of the local prototype. Conclusion: The differences in the biomechanical performance between the iFIX and Roger-Anderson clamps may be attributed to variations in clamp material composition. The iFIX fixator exhibited lower stiffness but did not display deformation under axial loading, component displaced slippage, or thread loosening, making it comparable to the commercial fixator.

Ballistic armors such as bulletproof vest, helmet, and shield are made up of composite materials which are reinforced with fibers having outstanding stiffness and strength, as well as excellent capability for absorbing the kinetic energy of the projectile. These properties make composite materials attractive in ballistic applications. The potential use of natural fibers in ballistic technologies offers several advantages because of their low processing cost, availability, lightweight properties, and good specific strength and modulus. In this study, an initial assessment of the ballistic performance of abaca fiber-reinforced epoxy matrix composite plates was investigated through finite element analysis using ANSYS engineering simulation software. Different fiber loadings were set at the following volume fractions: 30, 40, 50, and 60, since only a specific range of the amount of abaca fiber reinforcements can improve the mechanical properties such as the bullet impact energy resistance of the composite plates. Based on the results of the numerical simulations, the bullet impact resistance of the composite plates increased with the increase of fiber loading. Future direction of the study will involve the investigation on the effect of hybridization of different fiber types, polymer matrices and thickness of fiber-reinforced composite plates on their impact resistance and other mechanical properties.