Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Self-Propulsion of Droplets by Spatially-Varying Roughness   Under partial wetting conditions, making a substrate uniformly rougher
enhances the wetting characteristics of the corresponding smooth substrate {--}
hydrophilic systems become even more hydrophilic and hydrophobic systems even
more hydrophobic. Here we show that spatial texturing of the roughness may lead
to spontaneous propulsion of droplets. Individual droplets are driven toward
regions of maximal roughness for intrinsically hydrophilic systems and toward
regions of minimal roughness for intrinsically hydrophobic systems. Spatial
texturing can be achieved by wrinkling the substrate with sinusoidal grooves
whose wavelength varies in one direction (inhomogeneous wrinkling) or
lithographically etching a radial pattern of fractal (Koch curve) grooves on
the substrate. Richer energy landscapes for droplet trajectories can be
designed by combining roughness texturing with chemical or material patterning
of the substrate.

28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph