Sustainable Biofilm Inhibition Using Chitosan-Mesoporous Nanoparticle-Based Hybrid Slippery Composites.

In recent decades, extensive research has been directed toward mitigating microbial contamination and preventing biofilm formation. However, many conventional antibiofilm methods rely on hazardous and toxic substances, neglecting potential risks to human health and the environment. Moreover, these approaches often rely on single-strategy mechanisms, utilizing either bactericidal or fouling-resistant agents, which have shown limited efficacy in long-term biofilm suppression. In this study, we propose an efficient and sustainable biofilm-resistant slippery hybrid slippery composite. This composite integrates nontoxic and environmentally friendly materials including chitosan, silicone oil-infused polydimethylsiloxane, and mesoporous silica nanoparticles in a synergistic manner. Leveraging the bacteria-killing properties of chitosan and the antifouling capabilities of the silicone oil layer, the hybrid composite exhibits robust antibiofilm performance against both Gram-positive and Gram-negative bacteria. Furthermore, the inclusion of mesoporous silica nanoparticles enhances the oil absorption capacity and self-replenishing properties, ensuring exceptional biofilm inhibition even under harsh conditions such as exposure to high shear flow and prolonged incubation (7 days). This approach offers promising prospects for developing effective biofilm-resistant materials with a reduced environmental impact and improved long-term performance.

Water Skating Miniature Robot Propelled by Acoustic Bubbles.

This paper presents a miniature robot designed for monitoring its surroundings and exploring small and complex environments by skating on the surface of water. The robot is mainly made of extruded polystyrene insulation (XPS) and Teflon tubes and is propelled by acoustic bubble-induced microstreaming flows generated by gaseous bubbles trapped in the Teflon tubes. The robot's linear motion, velocity, and rotational motion are tested and measured at different frequencies and voltages. The results show that the propulsion velocity is proportional to the applied voltage but highly depends on the applied frequency. The maximum velocity occurs between the resonant frequencies for two bubbles trapped in Teflon tubes of different lengths. The robot's maneuvering capability is demonstrated by selective bubble excitation based on the concept of different resonant frequencies for bubbles of different volumes. The proposed water skating robot can perform linear propulsion, rotation, and 2D navigation on the water surface, making it suitable for exploring small and complex water environments.

Optothermally pulsating microbubble-mediated micro-energy harvesting in underwater medium.

Despite the considerable research interest due to practical importance of pervasive wireless sensing systems in a wide range of engineering fields, power management remains an arduous task for further development of pervasive wireless sensing systems due to inherent needs for self-reliant functionality and portability during their operations. To this end, we here propose a new type of energy harvesting strategy in which an optothermally pulsating microbubble is submerged in an underwater medium. The pulsating microbubble gives rise to the periodic vibration of piezocantilevers in contact, which resultantly can produce electrical outputs. On the basis of this simple idea, mechanical power can be extracted from light energy through optothermally pulsating microbubbles in an aqueous medium and subsequently the mechanical power can be converted to electrical power for wireless devices. To elucidate physical factors affecting the performance of the proposed strategy, we thoroughly explore the effect of the intensity and frequency of the laser beam on the pulsation amplitude of optothermally pulsating bubbles and subsequent electrical outputs (e.g., electrical voltage and power). The dependence of electrical output on wetting property of piezocantilevers and electrical resistance is also established. The present work would provide a new framework for fundamental design of bubble-based microactuators as energy harvesters and microsensors in the near future.