Rational fabrication, assembling and actuation of nanowire multi-mer nanomotors
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Direct field induced manipulations of nanowires have been recognized as a possible alternative to conventional chemical based assembling techniques. In particular, manipulation of nanowires with an external electric field allows the facile and precision assembly of nanowires into various nanoscale devices. In this study, we have rationally synthesized multisegment Au/Ni nanowires and assembled them into a unique type of rotary nanomotors made of nanowire multi-mers with designed geometric configurations by the electric tweezers. The electric tweezers are a recent invention developed by Prof. Fan’s group, which are based on the combined electrophoretic and dielectrophoretic forces to transport and align nanowires independently in low Reynolds number suspensions. The Au/Ni multi-segmented nanowires are rationally designed and fabricated by electrodeposition into nanoporous templates. By employing the ferromagnetic properties of the nickel segments in the nanowires, we precisely transported and assembled randomly disperse nanowires into multi-mer nanowire devices with designed configuration and further assembled them as the rotors of nanomotors. The magnetic attraction between the Ni segments in the nanowires holds the joints of dimers, trimers and tetramers tightly. The rotary nanomotors made of multiple assembled nanowires with designed configuration are the first to the best of our knowledge. Our study of their rotation behaviors as functions of voltage and frequency shows that the rotational speed of the nanomotors linearly increases with the square of the applied AC voltages and depends on the AC frequencies. The voltage square dependence is highly desirable for achieving ultrahigh speed rotation. This research could generate interest and impact multiple research fields including nanoelectromechanical system (NEMS) devices, nanomotors, microfluidic architectures and single-cell biology.