Zaki Saptari Saldi

In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films embedded with silver nanoparticles were fabricated to investigate their antibacterial performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Inspired by the nanoscale topographies of natural antibacterial surfaces, such as dragonfly and cicada wings, microstructured pillars were introduced onto the polymer surface to enhance its bactericidal activity by increasing the effective contact area. Surface morphology was characterised using scanning electron microscopy (SEM), including higher-magnification imaging of micropillar surfaces, while energy-dispersive X-ray spectroscopy confirmed the presence of silver. Higher-magnification SEM revealed nanoscale surface features on the micropillars, attributed to embedded or surface-associated silver nanoparticles. Antibacterial performance was evaluated using confocal laser scanning microscopy with live/dead staining. The PVDF-HFP/Ag films exhibited a significant reduction in bacterial viability, particularly against S. aureus (reducing viability to 0.6% ± 1.1%), while showing moderate activity against E. coli (41.0% ± 3.7% viability). While the fabricated micropillars (~5 µm) are larger than bacterial cells and unlikely to induce direct mechanical rupture, they increase surface interaction. To further investigate the theoretical antibacterial mechanism of scaled-down features, finite element analysis (FEA) was performed to model the mechanical interaction between bacterial cells and nanostructured pillars. The simulation results indicated localised stress concentrations that could compromise bacterial membrane integrity, suggesting a possible mechanobactericidal contribution if the microstructures are further reduced to the nanoscale, in addition to the primary biochemical effects of silver nanoparticles. FEA results do not aim to explain the experimentally observed antibacterial performance and should be interpreted only as a conceptual investigation. These findings demonstrate the potential of bio-inspired PVDF-HFP/Ag films as antibacterial materials for food packaging and related applications, subject to future comprehensive toxicity and quantitative microbiological evaluations.

Food packaging is essential for ensuring food safety and quality throughout the supply chain. However, the widespread use of petroleum‐based polymers has raised significant environmental concerns. As a result, bio‐based polymers have emerged as a sustainable alternative due to their biodegradability and biocompatibility, offering a potential solution to plastic pollution. Additionally, the incorporation of antimicrobial agents into packaging systems is crucial for controlling microbial contamination and extending food shelf life. These agents, including inorganic nanoparticles (e.g., metallic and metal oxides) and organic natural‐based compounds, have shown effectiveness in inhibiting microbial growth and mitigating biological contamination. This review highlights recent advances in bio‐based polymers and antimicrobial agents, focusing on materials that are both safe and environmentally friendly. It examines various methods for incorporating antimicrobial agents, particularly those derived from natural sources, into food packaging to develop fully bio‐based solutions. Moreover, this review addresses the challenges associated with fabricating packaging films tailored for specific products, as well as the future prospects for large‐scale, sustainable applications in the food packaging industry. By analyzing the performance of these materials and methodologies, the review aims to provide insights into the potential of bio‐based antimicrobial packaging in advancing sustainable food packaging technologies.

Prototyping plays an important role in product design and has recently gained benefit from the rising popularity of 3D printing. It is to be expected that 3D printing will accommodate more materials, which need to be tailored to specific design requirements. Insights into heat transfer and fluid flows (thermo-fluid dynamics) in the printing process is thus essential to obtain favorable process parameters that can lead to high quality prints. In this work, polylactic acid (PLA) melt in Fused Filament Fabrication (FFF) 3D printing was numerically studied through Computational Fluid Dynamics (CFD) simulations, with a focus on the thermo-fluid dynamics of the strand deposition of the filament melt on the printer platform. The study was carried out by evaluating 6 printing cases, with a variation of 2 key process parameters, i.e., printing speed (30 and 45 mm/s) and platform temperature (310, 320, and 340 K). The simulation results showed that the free surface in the tip region of the strand has the most tendency to adhere to the printing platform heated at 340 K with the printing speed of 45 mm/s, as compared with other cases. This was affected by the lower dynamic viscosity in the region, relative to other cases, resulting from the high platform temperature and shear rate generated by the high printing speed.

Liquid-carrying robots require slosh suppression methods to improve their performance. To design these systems requires effective slosh measurement. State-of-the-Art slosh estimation methods have limitations, which include solely handling unidirectional motion or relying on theoretical models. This letter proposes a novel sensor array for measuring sloshing in liquid-carrying mobile robots. The proposed system offers two key contributions: first, it enables comprehensive measurement and visualization of sloshing during omnidirectional movements, and second, it provides a compact and seamless integration into mobile robots, enabling them to mitigate the adverse effects of sloshing. The sensor system has been developed using 14 time-of-flight range sensors. The range sensors are connected to an Arduino Mega through I$^{2}$ C communication. A 3-D visualization method has also been developed to visualize the sloshing. The sensor array was integrated into a mobile robot for validation. Utilizing the 3-D visualization method, the sensor system can reconstruct the liquid surface with a sampling rate of 17.8 Hz. The experimental results confirm that the proposed sensor system effectively measures sloshing during omnidirectional movement of the robot.

Polylactide materials present a promising alternative to petroleum-based polymers due to their sustainability and biodegradability, although they have certain limitations in physical and mechanical properties for specific applications. The incorporation of nanoparticles, such as layered silicate (clay), carbon nanotubes, metal or metal oxide, cellulose nanowhiskers, can address these limitations by enhancing the thermal, mechanicals, barriers, and some other properties of polylactide. However, the distinct characteristics of these nanoparticles can affect the compatibility and processing of polylactide blends. In the polylactide nanocomposites, well-dispersed nanoparticles within the polylactide matrix result in excellent mechanical and thermal properties of the materials. Surface modification is required to improve compatibility and the crystallization process in the blended materials. This article reviews the development of polylactide nanocomposites and their applications. It discusses the general aspect of polylactides and nanomaterials as nanofillers, followed by the discussion of the processing and characterization of polylactide nanocomposites, including their applications. The final section summarizes and discusses the future challenges of polylactide nanocomposites concerning the future material’s requirements and economic considerations. As eco-friendly materials, polylactide nanocomposites offer significant potential to replace petroleum-based polymers.

For glass façade cleaning, we developed a reconfigurable robot, Mantis-mini, with a dry cleaning mechanism and linear actuator based transitioning mechanism. It consists of three suction modules, connected by a support structure and each suction module has individual differential drive wheels with independent steering capability. This paper focuses on the detailed design of the platform, static structural analysis for and kinematic formulation. The adhesion performance of the suction module is evaluated using experiments, Computational Fluid Dynamics (CFD) simulations, and analytically formulated estimation. The suction pressure magnitude predicted from the simulations increases with suction impeller speed and agrees well with measurements and analytical calculation in terms of order of magnitude and qualitative trend. An adaptive proportional-integral (PI) controller is designed and implemented for regulating suction pressure and motion controller of the platform. The suction performance of the platform is validated through real-time experiments of the platform on the glass surface.