Stephen J. Ebbens Jonathan Howse The current state of the art in nanopropulsion devices was recently reviewed by Ebbens and Howse in an article last Friday.[SoftMatter] A short summary of the nano- systems is presented below with video action shots when I could find them. The Whitesides Catalyst: Pt Fuel: H2O2 Propulsion: Bubble propulsion Terrain: Aqueous meniscus Max Speed: 2 cm/s Mitch’s Name: The Karl Benz (since it was the first) Article: Autonomous Movement and Self-Assembly The Sen-Mallouk-Crespi Catalyst: Pt Fuel: H2O2 Propulsion: Self electrophoresis/Interfacial tension Terrain: Settled near boundary in aqueous solution Max Speed: 6.6 um/s Mitch’s Names: The Ford Mustang of nanopropulsion. (It is a hot rod, get it?) Article: Catalytic Nanomotors: Autonomous Movement of Striped Nanorods The Jones-Golestanian Catalyst: Pt Fuel: H2O2 Propulsion: Pure self diffusiophoresis Terrain: Free aqueous solution Max Speed: 3um/s Mitch’s Name: The Volkswagen Beetle Article: Self-Motile Colloidal Particles: From Directed Propulsion to Random Walk The Mano-Heller Catalyst: Glucose oxidase and Biliruben oxidase Fuel: Glucose Propulsion: Self electrophoresis Terrain: Aqueous meniscus Max Speed: 1 cm/s Mitch’s Name: The Komatsu Truck (because it is huge) Article: Bioelectrochemical Propulsion The Feringa Catalyst: Synthetic catalse Fuel: H2O2 Propulsion: Bubble/interfacial Terrain: Acetonitrile solution Max Speed: 35 um/s Mitch’s...

Bradley Nelson The control of metallic flagella with magnetic fields is the subject of a recent paper by Li Zhang and Bradley Nelson.[NanoLett] The synthetic approach is a top-down process, and an image of a pre-released flagellum is shown below. Although typical bacteria like E. Coli are 1-2 μm long, this system is still a fascinatingly model of the motion of objects at low Reynolds numbers. The head of the artificial bacterium is composed of thin films of chromium, nickel, and gold. While the helical body is a composite of layers of indium gallium arsenide, gallium arsenide, and chromium. Motion is controlled by using three orthogonal electromagnetic coil pairs at 1-2 mT and a frequency of 5-35 Hz. A video of two of their flagella in action is shown below. A couple of other videos showing the ability of the authors to steer the flagella are provided here: 1 flagellum, 3 flagella. This system is a fascinating example of precise control of small devices that do not require outside chemical or photo sources. These systems have enormous promise and will likely comprise the type of motion the first nanorobots will utilize. One should couple this system to Gracias’ current generation of microgrippers for even more awesomeness. Link to the article is here: Characterizing the Swimming Properties of Artificial Bacterial Flagella Mitch