Micro/nanomotors are self-propelled machines that can convert various energy sources into autonomous movement. With the great advances of nanotechnology, Micro/Nanomotors of various geometries have been designed and fabricated over the past few decades. Among them, the tubular Micro/Nanomotors have a unique morphology of hollow structures, which enable them to possess a strong driving force and easy surface functionalization. They are promising for environmental and biomedical applications, ranging from water remediation, sensing to active drug delivery and precise surgery. This article gives a comprehensive and clear review of tubular Micro/Nanomotors, including propulsion mechanisms, fabrication techniques and applications. In the end, we also put forward some realistic problems and speculate about corresponding methods to improve existing tubular Micro/Nanomotors.

Switchable chemotaxis is vital for motile microorganisms seeking benefits or to avoid harm. Inspired by nature, and for the first time, we demonstrate an artificial enzyme-powered micromotor that can autonomously regulate the propulsion mechanism, as well as motion directionality, by solely sensing the change of fuel concentration (C_f) in its surroundings. The as-designed micromotors have a pot-like microstructure with ureases immobilized on the inner surface. With the confined effect of the pot-like microstructure and unique features of the urease catalytic reaction, the molecular products are further reacted into ions, and their propulsion mechanism can be reversibly adjusted between ionic diffusiophoresis and microbubble recoils when C_f changes. Consequently, the as-developed micromotors under magnetic field are able to self-turn back if the local C_f differs greatly in their surroundings, indicating the achievement of positive and negative chemotaxis by sensing local C_f. Meanwhile, the micromotors also show highly enhanced migration speed by microbubble ejection, up to 60 μm/s, around 30 body lengths per second at physiological urea concentrations. Furthermore, they have an outer surface of mesoporous silica which is easily functionalized for applications such as stimuli-responsive delivery-associated therapies. This work will promote “smart” artificial micro/nanomotors for in vivo biomedical applications.

Artificial nanomotors are nanoscale machines capable of converting surrounding other energy into mechanical motion and thus entering the tissues and cells of organisms. They hold great potential to revolutionize the diagnosis and treatment of diseases by actively targeting the lesion location, though there are many new challenges that arise with decreasing the size to nanoscale. This review summarizes and comments on the state‐of‐the‐art artificial nanomotors with advantages and limitations. It starts with the fabrication methods, including common physical vapor deposition and colloidal chemistry methods, followed by the locomotion characterization and motion manipulation. Then, the in vitro and in vivo biomedical applications are introduced in detail. The challenges and future prospects are discussed at the end.

This review highlights circulation, targeting, penetration, internalization, release, and treatment (CTPIRT process) of injectable nanorobots for precise cancer therapy.