Micromotor-mediated label-free cargo manipulation

Efficient and flexible cargo manipulation at the micro/nanoscale is key to the realization of an array of applications ranging from drug delivery, directed self-assembly, and environmental remediation to self-repair. In this review, we highlight recent advances in the label-free manipulation of cargo by microscale carriers, commonly referred to as “micromotors” Label-free manipulation eliminates the need for tagging of cargo, enabling on-demand dynamic selectivity. Primary mechanisms include electrical, optical, hydrodynamical, and mechanical forcing. For the carrier, both self-propelling active particles moving in a uniform field and smart passive structures moving in a field gradient are considered with the caveat that cargo manipulation is “micromotor-mediated,” i.e., cargo is not manipulated directly by the applied fields but only through its interaction with the carrier. We compare the manipulation techniques in terms of selectivity, cargo size, material, and suspending medium. We conclude by summarizing the existing challenges and future prospects.