Reversed Janus Micro/Nanomotors with Internal Chemical Engine.
Self-motile Janus colloids are important for enabling a wide variety of microtechnology applications as well as for improving our understanding of the mechanisms of motion of artificial micro- and nanoswimmers. We present here micro/nanomotors which possess a reversed Janus structure of an internal catalytic "chemical engine". The catalytic material (here platinum (Pt)) is embedded within the interior of the mesoporous silica (mSiO2)-based hollow particles and triggers the decomposition of H2O2 when suspended in an aqueous peroxide (H2O2) solution. The pores/gaps at the noncatalytic (Pt) hemisphere allow the exchange of chemical species in solution between the exterior and the interior of the particle. By varying the diameter of the particles, we observed size-dependent motile behavior in the form of enhanced diffusion for 500 nm particles, and self-phoretic motion, toward the nonmetallic part, for 1.5 and 3 μm ones. The direction of motion was rationalized by a theoretical model based on self-phoresis. For the 3 μm particles, a change in the morphology of the porous part is observed, which is accompanied by a change in the mechanism of propulsion via bubble nucleation and ejection as well as a change in the direction of motion.
Max-Planck Institute for Intelligent Systems , Heisenbergstraße 3, 70569 Stuttgart, Germany.
Xing
X
Ma
Max-Planck Institute for Intelligent Systems , Heisenbergstraße 3, 70569 Stuttgart, Germany.|Center of Applied Microfluidic Chemistry, Department of Chemical Engineering, Pohang University of Science and Technology , 77 Cheongam-ro, Nam-gu, 37673 Pohang, South Korea.
Seungwook
S
Jang
Max-Planck Institute for Intelligent Systems , Heisenbergstraße 3, 70569 Stuttgart, Germany.|IV. Institut für Theoretische Physik, Universität Stuttgart , Pfaffenwaldring 57, D-70569 Stuttgart, Germany.
Mihail N
MN
Popescu
Max-Planck Institute for Intelligent Systems , Heisenbergstraße 3, 70569 Stuttgart, Germany.|IV. Institut für Theoretische Physik, Universität Stuttgart , Pfaffenwaldring 57, D-70569 Stuttgart, Germany.
William E
WE
Uspal
Institut de Bioenginyeria de Catalunya (IBEC) , Baldiri i Reixac 10-12, 08028 Barcelona, Spain.
Albert
A
Miguel-López
Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research , Heisenbergstraße 1, 70569 Stuttgart, Germany.
Kersten
K
Hahn
Max-Planck Institute for Intelligent Systems , Heisenbergstraße 3, 70569 Stuttgart, Germany.|Center of Applied Microfluidic Chemistry, Department of Chemical Engineering, Pohang University of Science and Technology , 77 Cheongam-ro, Nam-gu, 37673 Pohang, South Korea.
Dong-Pyo
DP
Kim
Max-Planck Institute for Intelligent Systems , Heisenbergstraße 3, 70569 Stuttgart, Germany.|Institut de Bioenginyeria de Catalunya (IBEC) , Baldiri i Reixac 10-12, 08028 Barcelona, Spain.|Institució Catalana de Recerca i Estudis Avancats (ICREA) , Pg. Lluís Companys 23, 08010 Barcelona, Spain.
Samuel
S
Sánchez
Janus particles; mesoporous silica; micro/nanomotors; micromachines; phoretic motion; self-propulsion