title: Nanopropellers and their actuation in complex viscoelastic media.
abstract: Tissue and biological fluids are complex viscoelastic media with a nanoporous macromolecular structure. Here, we demonstrate that helical nanopropellers can be controllably steered through such a biological gel. The screw-propellers have a filament diameter of about 70 nm and are smaller than previously reported nanopropellers as well as any swimming microorganism. We show that the nanoscrews will move through high-viscosity solutions with comparable velocities to that of larger micropropellers, even though they are so small that Brownian forces suppress their actuation in pure water. When actuated in viscoelastic hyaluronan gels, the nanopropellers appear to have a significant advantage, as they are of the same size range as the gel's mesh size. Whereas larger helices will show very low or negligible propulsion in hyaluronan solutions, the nanoscrews actually display significantly enhanced propulsion velocities that exceed the highest measured speeds in Newtonian fluids. The nanopropellers are not only promising for applications in the extracellular environment but small enough to be taken up by cells.
authors.affiliation: Max Planck Institute for Intelligent Systems , Heisenbergstraße 3, 70569 Stuttgart, Germany.
authors.forename: Debora
authors.initials: D
authors.lastname: Schamel
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Mark
authors.forename: John G
authors.initials: JG
authors.lastname: Gibbs
authors.forename: Cornelia
authors.initials: C
authors.lastname: Miksch
authors.forename: Konstantin I
authors.initials: KI
authors.lastname: Morozov
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Leshansky
authors.forename: Peer
authors.initials: P
authors.lastname: Fischer
mesh_terms: D004548:Elasticity; D060328:Magnetic Phenomena; D009038:Motion; D036103:Nanotechnology / Q000295:instrumentation*; D012212:Rheology; D014783:Viscosity; D014867:Water
chemical_list: D014867:Water
keywords: Brownian motion; glancing angle deposition; magnetic actuation; micropropulsion; polymeric networks; vapor deposition; viscoelastic fluids