In recent years, jointless soft robots have demonstrated various curvilinear motions unlike conventional robotic systems requiring complex mechanical joints and electrical design principles. The materials employed to construct soft robots are mainly programmable anisotropic polymeric materials to achieve contactless manipulation of miniaturized and lightweight soft robots through their anisotropic strain responsivity to external stimuli. Although reviews on soft actuators are extensive, those on untethered soft robots are scant. In this study, we focus on the recent progress in the manipulation of untethered soft robots upon receiving external stimuli such as magnetic fields, light, humidity, and organic solvents. For each external stimulus, we provide an overview of the working principles along with the characteristics of programmable anisotropic materials and polymeric composites used in soft robotic systems. In addition, potential applications for untethered soft robots are discussed based on the physicochemical properties of programmable anisotropic materials for the given external stimuli.

The functional surface features of living creatures are driven by the complex morphology of periodically arranged micro/nanoscale structures. Various fabrication processes have been devised mimic the performance of natural features; these methods morph hierarchical and multi‐leveled pillar arrays, such as top‐down, bottom‐up, and a hybrid of top‐down and bottom‐up processes. Different methodologies are employed depending on the materials, such as polymeric composites, metal oxides, metals, and carbon nanotubes. In this review, we discuss the shape‐reconfiguration of stimuli‐responsive micro/nanopillar arrays achieved by capillary force, light, magnetic field, and heat. In particular, photo‐ and magnetic actuation of pillar arrays revealed programmability according to the arrangement of the liquid crystal molecules or magnetic particles by remote control. Furthermore, applications of micro/nanopillar arrays, such as adhesives, omniphobicity, optics, and biomedical technologies, are also discussed.

In aqueous media, liquid crystalline droplets typically form spherical shapes in order to minimize surface energy. Recently, non-spherical geometry has been reported using molecular self-assembly of surfactant-stabilized liquid crystalline oligomers, resulting in branched and randomly oriented filamentous networks. In this study, we report a polymerization of liquid crystalline polymeric fibers within a micro-mold. When liquid crystal oligomers are polymerized in freely suspended aqueous media, curvilinear and randomly networked filaments are obtained. When reactive liquid crystalline monomers are oligomerized in a micro-channel, however, highly aligned linear fibers are polymerized. Within a top-down microfabricated mold, a bottom-up molecular assembly was successfully achieved in a controlled manner by micro-confinement, suggesting a unique opportunity for the programming architecture of materials via a hybrid approach.