Inspired by the natural design of bacterial flagella, we report artificial bacterial flagella (ABF) that have a comparable shape and size to their organic counterparts and can swim in a controllable fashion using weak applied magnetic fields. The helical swimmer consists of a helical tail resembling the dimensions of a natural flagellum and a thin soft-magnetic “head” on one end. The swimming locomotion of ABF is precisely controlled by three orthogonal electromagnetic coil pairs. Microsphere manipulation is performed, and the thrust force generated by an ABF is analyzed. ABF swimmers represent the first demonstration of microscopic artificial swimmers that use helical propulsion. Self-propelled devices such as these are of interest in fundamental research and for biomedical applications.

Magnetic microrobot swarms collectively perform tasks in a confined environment through multimode transformation and locomotion.

Microrobots have the potential to dramatically change many aspects of medicine by navigating through bodily fluids to perform targeted diagnosis and therapy. Researchers have proposed numerous micro-robotic swimming methods, with the vast majority utilizing magnetic fields to wirelessly power and control the microrobot. In this paper, we compare three promising methods of microrobot swimming (using magnetic fields to rotate helical propellers that mimic bacterial flagella, using magnetic fields to oscillate a magnetic head with a rigidly attached elastic tail, and pulling directly with magnetic field gradients) considering practical hardware limitations in the generation of magnetic fields. We find that helical propellers and elastic tails have very comparable performance, and they generally become more desirable than gradient pulling as size decreases and as distance from the magnetic-field-generation source increases. We provide a discussion of why helical propellers are likely the best overall choice for in vivo applications.

Properties and potential applications of carbon nanotubes are summarized by emphasizing the aspects of nanoelectronics and nanoelectromechanical systems (NEMS). The main technologies for the assembly of nanodevices through nanomanipulations with scanning probe microscopes and nanorobotic manipulators are overviewed, focusing on that of nanotubes. Key techniques for nanoassembly include the preparation of nano building blocks and property characterization of them, the positioning of the building blocks with nanometer-scale resolution, and the connection of them. Nanorobotic manipulations, which are characterized by multiple degrees of freedom (DOFs) with both position and orientation control, independently actuated multiprobes, and a real-time observation system, are one of the most promising technologies for assembling complex nanodevices in three-dimensional space. With a nano laboratory, a prototype nanomanufacturing system based on a 16-DOF nanorobotic manipulation system, the assembly of nanodevices with multiwalled carbon nanotubes are presented. Nanotube-based building blocks are prepared by directly picking up, in situ property characterization, destructive fabrication, and shape modifications. Kinds of nanotube junctions, the fundamental elements for both nanoelectronics and NEMS, are constructed by positioning the building blocks together under the real-time observation with a field-emission scanning electron microscope, connecting them with naturally existing van der Waals forces, electron-beam-induced deposition, or mechanochemical bonding.