Visible-Light-Driven Asymmetric TiO2-Based Photocatalytic Micromotor Hybridized with a Conjugated Polyelectrolyte and Glucose Oxidase

Synthesis and application of titanium dioxide photocatalysis for energy, decontamination and viral disinfection: a review

Global pollution is calling for advanced methods to remove contaminants from water and wastewater, such as TiO₂-assisted photocatalysis.  The environmental applications of titanium dioxide have started after the initial TiO₂ application for water splitting by Fujishima and Honda in 1972. TiO₂ is now used for self-cleaning surfaces, air and water purification systems, microbial inactivation and selective organic conversion. The synthesis of titanium dioxide nanomaterials with high photocatalytic activity is actually a major challenge. Here we review titanium dioxide photocatalysis with focus on mechanims, synthesis, and applications. Synthetic methods include sol-gel, sonochemical, microwave, oxidation, deposition, hydro/solvothermal, and biological techniques. Applications comprise the production of energy, petroleum recovery, and the removal of microplastics, pharmaceuticals, metals, dyes, pesticides, and of viruses such as the severe acute respiratory syndrome coronavirus 2.

Interactive and synergistic behaviours of multiple heterogeneous microrobots

Microrobots have been extensively studied for biomedical applications, and significant innovations and advances have been made in diverse aspects of the field. However, most studies have been based on individual microrobots with limited capabilities, constraining their scalability of functions for practical use. Here, we demonstrate the interactive and synergistic behaviours of multiple microrobots that are heterogeneous or incompletely homogeneous. A frequency-response theory is proposed where in a certain frequency range of an external rotating magnetic field (RMF), microrobots with dispersed and linearly aligned magnetic nanoparticles (MNPs) would exhibit similar and different behaviour, respectively. These microrobots rotate following the rotation of the external field, and such complete rotational motion is interrupted when the frequency exceeds a certain value, called the critical frequency (c_f), but such behaviour is more prominent in microrobots with linear MNPs. Upon further investigating the effect of various parameters on the c_f of the microrobots during the fabrication process, we find that heterogeneous microrobots with specific c_f values can be customized. In addition, experiments and simulations are combined to show the hydrodynamic behaviours around the rotating microrobots at different frequencies. Based on these findings, the interactive and synergistic behaviours of multiple microrobots are presented, which suggests great potential for the independent execution of multiple tasks or the synergistic performance of complex tasks and is significant for the future development of interactive synergistic microrobots in the biomedical field.

Enzyme-powered micro- and nano-motors: key parameters for an application-oriented design

Nature has inspired the creation of artificial micro- and nanomotors that self-propel converting chemical energy into mechanical action. These tiny machines have appeared as promising biomedical tools for treatment and diagnosis and have also been used for environmental, antimicrobial or sensing applications. Among the possible catalytic engines, enzymes have emerged as an alternative to inorganic catalysts due to their biocompatibility and the variety and bioavailability of fuels. Although the field of enzyme-powered micro- and nano-motors has a trajectory of more than a decade, a comprehensive framework on how to rationally design, control and optimize their motion is still missing. With this purpose, herein we performed a thorough bibliographic study on the key parameters governing the propulsion of these enzyme-powered devices, namely the chassis shape, the material composition, the motor size, the enzyme type, the method used to incorporate enzymes, the distribution of the product released, the motion mechanism, the motion media and the technique used for motion detection. In conclusion, from the library of options that each parameter offers there needs to be a rational selection and intelligent design of enzymatic motors based on the specific application envisioned.