Light‐Driven Janus Hollow Mesoporous TiO₂–Au Microswimmers

Abstract

Light‐driven microswimmers have garnered attention for their potential use in various applications, such as environmental remediation, hydrogen evolution, and targeted drug delivery. Janus hollow mesoporous TiO2/Au (JHP–TiO2–Au) microswimmers with enhanced swimming speeds under low‐intensity ultraviolet (UV) light are presented. The swimmers show enhanced swimming speeds both in presence and absence of H2O2. The microswimmers move due to self‐electrophoresis when UV light is incident on them. There is a threefold increase in speed of JHP–TiO2–Au microswimmers in comparison with Janus solid TiO2/Au (JS–TiO2–Au) microswimmers. This increase in their speed is due to the increase in surface area of the porous swimmers and their hollow structure. These microswimmers are also made steerable by using a thin Co magnetic layer. They can be used in potential environmental applications for active photocatalytic degradation of methylene blue and targeted active drug delivery of an anticancer drug (doxurobicin) in vitro in H2O2 solution. Their increased speed from the presence of a hollow mesoporous structure is beneficial for future potential applications, such as hydrogen evolution, selective heterogeneous photocatalysis, and targeted cargo delivery.

Catalytic and Light‐Driven ZnO/Pt Janus Nano/Micromotors: Switching of Motion Mechanism via Interface Roughness and Defect Tailoring at the Nanoscale

“…There are a few papers that show the influence of interface nanostructure on the motion of the catalytic nano/micromotors . The mesoporous structure together with the interfaces has even been lesser addressed for the case of light‐driven micromotors, which should play the dominant role on the self‐propulsion . In this paper, we synthesize mesoporous ZnO/Pt micromotor models with specific surface/interface morphologies to study their fuel‐dependent propulsive behavior under light exposure ( Scheme ).…”

“…Although H 2 O 2 is used as a common fuel in Fenton reactions for large‐scale wastewater treatment, its use as a catalytic fuel for micromotors in biomedical applications might lead to a risk of introducing toxic species into living organisms . The light energy source is renewable, powerful, and abundant, which meets the energy requirements for water purification, and meanwhile it is harmless for living organisms . Light not only can be converted into a directional motion by photoresponsive micromotors, but it can also be applied to induce the photodegradation of different pollutants in water‐purification processes …”

Acoustically powered surface-slipping mobile microrobots

“…microrobots | acoustic actuation | magnetic control | microswimmers | bubble oscillation U ntethered synthetic microrobots have been recently investigated for their potential applications in targeted drug delivery, detoxification, and noninvasive surgeries (1)(2)(3)(4). The existing microswimmers are powered by different external energy sources, such as light (5)(6)(7), electrical (8,9), magnetic (10,11), and acoustic (12,13) fields, or fueled by chemicals in the environment (14,15). Among these actuation schemes, magnetic and acoustic field-based powering methods are the most prevalent in the biomedical context thanks to their deep-tissue penetration and high-energy-density capabilities.…”

Pros and Cons: Magnetic versus Optical Microrobots

“…Such a property is very advantageous for safe medical applications, where the robot can be fully stopped in case of any emergency if the external energy source is turned off. However, if the light is used to propel a microparticle using photocatalytic effects,77 the optical actuation can create independent self‐propelled autonomous microswimmers. The advantage of such photocatalytic microswimmers is enabling autonomous swimming behavior, while still being able to be stopped from outside in case of emergency.…”