This paper presents a manipulation system capable of five degree of freedom (5-DOF) control of a magnetic nanoagent (3-DOF position, 2-DOF orientation) implemented on an inverted microscope. Magnetic fields up to 50 mT and gradients up to 5 T/m at frequencies up to 6 kHz can be achieved. The independent generation of field and gradient vectors enables holonomic 5-DOF wireless magnetic manipulation at the nanoscale. Multiple types of motion were investigated for nickel nanowires of different lengths and analyzed using resistive force theory.

Swimming microrobots have the potential to be used in medical applications such as targeted drug delivery. The challenges for navigating microrobots in the human body lie not only in the viscosity of body fluids but also in the existence of different types of fibers and cells such as blood cells or protein strands. This paper investigates artificial bacterial flagella (ABFs), which are helical microrobots actuated by an external magnetic field, in methyl cellulose solutions of different concentrations. It can be shown that the microrobots can be propelled in these gel-like heterogeneous solutions and successful swimming was demonstrated in solutions with a viscosity of more than 20 times that of water. Furthermore, results indicate that the existence of fibers can help ABFs swim more effectively, which agrees with previous experimental results reported for natural bacteria.

The artificial bacterial flagellum (ABF), a helical swimming microrobot, has the potential to be used for biomedical applications such as cellular and intracellular manipulation. The velocity and the propulsive force of the ABF can be controlled by the input frequency of the rotating magnetic field. In this paper the swimming behavior of the ABF near a solid surface is reported. Three regions have been observed for the frequency-dependent swimming behavior of the ABF, i.e. the step-out, the linear and the drift-dominated region. At low frequencies it has been found that the desired screw-type motion is replaced by a wobbling swimming movement with a frequency-dependent precession angle. Moreover, the experimental results show that the wobbling motion of the ABF enhances the undesired sidewise drift due to wall effects. Additionally, the cause of the precession motion has been investigated by a hydrodynamic model. Our results imply that the linear range of the input magnetic frequency and the output ABF velocity is not only limited by the applicable torque at high frequencies but also by the wobbling of helical swimming at low frequencies.

Artificial bacterial flagella (ABF) are swimming microrobots that mimic the swimming motion of bacteria. The helical swimmer consists of an InGaAs/GaAs/Cr helical nanobelt tail fabricated by a self-scrolling technique with dimensions similar to a natural flagellum, and a thin soft-magnetic metal ¿head¿ consisting of a Cr/Ni/Au multi-layer. The swimming locomotion of ABF is precisely controlled in 3-D by external rotating magnetic fields. Microsphere manipulation is performed by ABF, and experimental results show that both the position and the orientation of microspheres can be precisely controlled. The propelling force of ABF is in the pico-Newton range. We also describe a swarm-like behavior in which three ABF swim in a pack, indicating the potential to handle several micro objects in parallel. Self-propelled devices such as these are candidates for wireless 6-DOF micro and nanomanipulation tools for handling cellular and sub-cellular objects.