Soft Micro- and Nanorobotics

Micro- and nanorobots can perform a number of tasks at small scales, such as minimally invasive diagnostics, targeted drug delivery, and localized surgery. During the past decade, the field has been transformed in many ways, one of the most significant being a transition from hard and rigid micro- and nanostructures to soft and flexible architectures. Inspired by the dynamics of flexible microorganisms, researchers have focused on developing miniaturized soft components such as actuators, sensors, hinges, joints, and reservoirs to create soft micro- and nanoswimmers. The use of organic structures such as polymers and supramolecular ensembles as functional components has brought more complex features to these devices, such as advanced locomotion strategies and stimulus-triggered shape transformations, as well as other capabilities. A variety of microorganisms and contractile mammalian cells have also been utilized as microengines and integrated with functional synthetic materials, producing bending or deformation of the functional materials to initiate motion. In this review, we consider several types of soft micro- and nanorobots in terms of their architecture and design, and we describe their locomotion mechanisms and applications.