Self-propelled nano- and micromachines have immense potential as autonomous seek-and-act devices in biomedical applications. In this study, we present microrobots constructed with inherently biocompatible materials and propulsion systems tailored to skin-related applications. Addressing the significant treatment challenge posed by methicillin-resistant Staphylococcus aureus (MRSA) skin infections, we demonstrate that photocatalytic titanium dioxide microrobots decorated with silver or platinum can effectively and rapidly eradicate MRSA biofilms grown on skin-mimicking membranes and porcine skin tissues. These microrobots are powered by hydrogen peroxide or ultraviolet light─agents considered toxic in high concentrations but commonly used in controlled amounts for skin disinfection and naturally encountered by the skin. By examining the effects of different metal coatings on the propulsion abilities of the microrobots, we show that these chemically propelled devices can eliminate biofilms without causing significant damage to the surrounding skin tissues, as confirmed by histological analysis. This work paves the way for the use of microrobots in skin-related biomedical applications, particularly in cases where traditional antibiotics are ineffective.

• Keywords
• Janus particles, biofilm, microrobots, skin infection, titanium dioxide,
• MeSH
• Anti-Bacterial Agents * pharmacology   chemistry   MeSH
• Biofilms drug effects   MeSH
• Skin * microbiology   drug effects   MeSH
• Methicillin-Resistant Staphylococcus aureus * drug effects   physiology   MeSH
• Hydrogen Peroxide chemistry   pharmacology   MeSH
• Platinum chemistry   pharmacology   MeSH
• Swine MeSH
• Robotics * instrumentation   MeSH
• Staphylococcal Skin Infections * drug therapy   microbiology   MeSH
• Silver chemistry   pharmacology   MeSH
• Titanium chemistry   pharmacology   MeSH
• Ultraviolet Rays MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents * MeSH
• Hydrogen Peroxide MeSH
• Platinum MeSH
• Silver MeSH
• Titanium MeSH
• titanium dioxide MeSH Browser

Bacterial biofilms are complex multicellular communities that adhere firmly to solid surfaces. They are widely recognized as major threats to human health, contributing to issues such as persistent infections on medical implants and severe contamination in drinking water systems. As a potential treatment for biofilms, this work proposes two strategies: (i) light-driven ZnFe2O4 (ZFO)/Pt microrobots for photodegradation of biofilms and (ii) magnetically driven ZFO microrobots for mechanical removal of biofilms from surfaces. Magnetically driven ZFO microrobots were realized by synthesizing ZFO microspheres through a low-cost and large-scale hydrothermal synthesis, followed by a calcination process. Then, a Pt layer was deposited on the surface of the ZFO microspheres to break their symmetry, resulting in self-propelled light-driven Janus ZFO/Pt microrobots. Light-driven ZFO/Pt microrobots exhibited active locomotion under UV light irradiation and controllable motion in terms of "stop and go" features. Magnetically driven ZFO microrobots were capable of maneuvering precisely when subjected to an external rotating magnetic field. These microrobots could eliminate Gram-negative Escherichia coli (E. coli) biofilms through photogenerated reactive oxygen species (ROS)-related antibacterial properties in combination with their light-powered active locomotion, accelerating the mass transfer to remove biofilms more effectively in water. Moreover, the actuation of magnetically driven ZFO microrobots allowed for the physical disruption of biofilms, which represents a reliable alternative to photocatalysis for the removal of strongly anchored biofilms in confined spaces. With their versatile characteristics, the envisioned microrobots highlight a significant potential for biofilm removal with high efficacy in both open and confined spaces, such as the pipelines of industrial plants.

• Keywords
• biofilm, collective motion, magnetically driven, micromotors, microrobots, photocatalysis,
• MeSH
• Anti-Bacterial Agents * pharmacology   chemistry   MeSH
• Biofilms * drug effects   MeSH
• Escherichia coli * drug effects   physiology   MeSH
• Microspheres MeSH
• Platinum chemistry   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Robotics * instrumentation   MeSH
• Ultraviolet Rays MeSH
• Ferric Compounds chemistry   pharmacology   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents * MeSH
• Platinum MeSH
• Reactive Oxygen Species MeSH
• Ferric Compounds MeSH

The forefront of micro- and nanorobot research involves the development of smart swimming micromachines emulating the complexity of natural systems, such as the swarming and collective behaviors typically observed in animals and microorganisms, for efficient task execution. This study introduces magnetically controlled microrobots that possess polymeric sequestrant "hands" decorating a magnetic core. Under the influence of external magnetic fields, the functionalized magnetic beads dynamically self-assemble from individual microparticles into well-defined rotating planes of diverse dimensions, allowing modulation of their propulsion speed, and exhibiting a collective motion. These mobile microrobotic swarms can actively capture free-swimming bacteria and dispersed microplastics "on-the-fly", thereby cleaning aquatic environments. Unlike conventional methods, these microrobots can be collected from the complex media and can release the captured contaminants in a second vessel in a controllable manner, that is, using ultrasound, offering a sustainable solution for repeated use in decontamination processes. Additionally, the residual water is subjected to UV irradiation to eliminate any remaining bacteria, providing a comprehensive cleaning solution. In summary, this study shows a swarming microrobot design for water decontamination processes.

• Keywords
• collective motion, magnetically driven, micromotors, microplastics, self-assembly, swarming behavior, water purification,
• MeSH
• Bacteria isolation & purification   MeSH
• Escherichia coli isolation & purification   MeSH
• Magnetic Fields MeSH
• Microplastics * chemistry   MeSH
• Polymers chemistry   MeSH
• Robotics * instrumentation   MeSH
• Particle Size MeSH
• Water chemistry   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

The development of artificial small-scale robotic swarms with nature-mimicking collective behaviors represents the frontier of research in robotics. While microrobot swarming under magnetic manipulation has been extensively explored, light-induced self-organization of micro- and nanorobots is still challenging. This study demonstrates the interaction-controlled, reconfigurable, reversible, and active self-assembly of TiO2/α-Fe2O3 microrobots, consisting of peanut-shaped α-Fe2O3 (hematite) microparticles synthesized by a hydrothermal method and covered with a thin layer of TiO2 by atomic layer deposition (ALD). Due to their photocatalytic and ferromagnetic properties, microrobots autonomously move in water under light irradiation, while a magnetic field precisely controls their direction. In the presence of H2O2 fuel, concentration gradients around the illuminated microrobots result in mutual attraction by phoretic interactions, inducing their spontaneous organization into self-propelled clusters. In the dark, clusters reversibly reconfigure into microchains where microrobots are aligned due to magnetic dipole-dipole interactions. Microrobots' active motion and photocatalytic properties were investigated for water remediation from pesticides, obtaining the rapid degradation of the extensively used, persistent, and hazardous herbicide 2,4-Dichlorophenoxyacetic acid (2,4D). This study potentially impacts the realization of future intelligent adaptive metamachines and the application of light-powered self-propelled micro- and nanomotors toward the degradation of persistent organic pollutants (POPs) or micro- and nanoplastics.

• Publication type
• Journal Article MeSH