Remote Manipulation of Droplets on a Flexible Magnetically Responsive Film

The manipulation of droplets is used in a wide range of applications, from lab-on-a-chip devices to bioinspired functional surfaces. Although a variety of droplet manipulation techniques have been proposed, active, fast and reversible manipulation of pure discrete droplets remains elusive due to the technical limitations of previous techniques. Here, we describe a novel technique that enables active, fast, precise and reversible control over the position and motion of a pure discrete droplet with only a permanent magnet by utilizing a magnetically responsive flexible film possessing actuating hierarchical pillars on the surface. This magnetically responsive surface shows reliable actuating capabilities with immediate field responses and maximum tilting angles of ???90??. Furthermore, the magnetic responsive film exhibits superhydrophobicity regardless of tilting angles of the actuating pillars. Using this magnetically responsive film, we demonstrate active and reversible manipulation of droplets with a remote magnetic force.open0

Hierarchical models of engineering rough surfaces and bio-inspired adhesives

Friction, wear, adhesion and energy dissipation during sliding are strongly influenced by deformations of asperities, which, in turn, depend on the surface profile. At the nanoscale, the effects of surface roughness and the underlying physical phenomena, such as adhesion between contacting objects, have a considerable influence on the interaction between surfaces. Here various models of rough surfaces, including multi-level models, hierarchically structured models, and appropriate multi-scale models of contact interactions between rough surfaces are reviewed and discussed. A new model for numerical simulations of dry friction between rough engineering surfaces is introduced. The main features of the new model based on the use of a multi-level and multi-scale, hierarchically structured slider are described. Although the surface topography of the biological attachment devices is rather different from the topography of engineering surfaces, some existing models of bio-inspired adhesives are classified using terminology introduced for models of engineering rough surfaces