Active Synthetic Microrotors: Design Strategies and Applications

Microrotors are microscopic objects that convert energystoredin the environment into spontaneous rotation, in the form of spinningalong an axis, rolling on a surface, or orbiting in circles. Becauseof its distinct dynamics and the vertical flows around it, a microrotoris potentially useful for applications, including drug delivery, minimallyinvasive surgery, fluid mixing, and sensing. It is also useful asa model system to probe the collective behaviors among rotating micro-objects.In this review article, we comprehensively review the recent experimentalprogress in designing, synthesizing, and using microrotors. For applications,particular emphasis is placed on microfluidic mixing, biomedicine,and collective behaviors. In the end, we comment on how microrotorscan be made more biocompatible and more controllable and rotate inmore ways and the challenges therein. A key feature of this reviewarticle is to introduce three ways in which to classify a microrotor:the nature of its rotational behavior (spinners, rollers, or orbiters),the cause of its rotation (whether chiral symmetry is broken by shapes,chemical compositions, or the way energy is applied), and its powersource (whether powered by chemical reactions, electric or magneticfields, light, or ultrasound). This review article will help materialsscientists and chemists in designing micromachines and microrotors,help engineers in finding appropriate microrotors for a specific application,and help physicists in finding appropriate model systems.

Automated summary

Microrotors are microscopic objects that convert energy stored in the environment into spontaneous rotation. They have various applications, including drug delivery, minimally invasive surgery, fluid mixing, and sensing. They are also useful as model systems to study collective behaviors among rotating micro-objects.