Material selection, preparation, driving and applications of light-driven micro/nano motors: a review

As an external energy stimulus, light possesses the advantageous qualities of being reversible, wireless and remotely maneuverable while driving the motion of micro and nano motors. Despite the extensive publication of articles on light-driven micro- and nano-motors (LDMNMs) over the past two decades, reviews that address LDMNMs in general, from material selection, design, preparation, driving to applications, remain scarce. Therefore, it is necessary to highlight the superiority of light as a stimulating energy source for driving MNMs, as well as to promote the continuous development of LDMNMs and give newcomers a more basic and comprehensive knowledge in this field. This present review focuses on advanced preparation methods for LDNMNs, and provides a comprehensive comparison of the advantages and limitations of various techniques. In addition, general design strategies for building asymmetric fields around LDMNMs are introduced, as well as a variety of photoactive materials, including photocatalytic, photothermal, and photoinduced isomerization materials. The existing propulsive mechanisms and kinematic behaviours of LDMNMs are described in detail, including photocatalytic oxidation, photothermal effects and photoinduced isomerization. The principles of the various drive mechanisms are also analysed in detail and their merits and shortcomings summarized. Finally, following a comprehensive review of the potential applications in biomedicine, environmental remediation and other fields, further perspectives on future developments are presented with a view to overcoming key challenges.