Motile Piezoelectric Nanoeels for Targeted Drug Delivery

The field of small-scale robotics is undergoing a paradigm shift toward the use of soft smart materials. The integration of soft smart components in micro- and nanorobotic platforms not only allows for more sophisticated locomotion mechanisms, but also more closely mimicks the functioning of biological systems. A soft hybrid nanorobot that mimics an electric eel, a knifefish with an elongated cylindrical body that is able to generate electricity during its motion, is presented here. These nanoeels consist of a flexible piezoelectric tail composed of a polyvinylidene fluoride-based copolymer, linked to a polypyrrole nanowire, which is decorated with nickel rings for magnetic actuation. Upon the application of rotating magnetic fields, the piezoelectric soft tail is deformed causing changes in its electric polarization. Capitalizing on this magnetically coupled piezoelectric effect, electrostatically enhanced on-demand release of therapeutic cargo loaded on the surface of the piezoelectric tail is demonstrated. It is also shown that this approach allows for a pulsatile release of payloads. Interestingly, the driving magnetic parameters can be selected to provide the nanoeel with translational motion or to control the discharge kinetics of the drug.