title: Slippery questions about complex fluids flowing past solids.
abstract: Viscous flow is familiar and useful, yet the underlying physics is surprisingly subtle and complex. Recent experiments and simulations show that the textbook assumption of 'no slip at the boundary' can fail greatly when walls are sufficiently smooth. The reasons for this seem to involve materials chemistry interactions that can be controlled--especially wettability and the presence of trace impurities, even of dissolved gases. To discover what boundary condition is appropriate for solving continuum equations requires investigation of microscopic particulars. Here, we draw attention to unresolved topics of investigation and to the potential to capitalize on 'slip at the wall' for purposes of materials engineering.
authors.affiliation: Department of Materials Science and Engineering, Chemistry and Physics, University of Illinois, Urbana, Illinois 61801 USA.
authors.forename: Steve
authors.initials: S
authors.lastname: Granick
authors.forename: Yingxi
authors.initials: Y
authors.lastname: Zhu
authors.forename: Hyunjung
authors.initials: H
authors.lastname: Lee
mesh_terms: D017276:Friction; D005740:Gases / Q000737:chemistry; D008422:Materials Testing / Q000379:methods*; D008962:Models, Theoretical; D010316:Particle Size; D012212:Rheology / Q000379:methods* / Q000639:trends; D033081:Shear Strength; D012996:Solutions / Q000737:chemistry*; D013499:Surface Properties; D014783:Viscosity; D017155:Wettability
chemical_list: D005740:Gases; D012996:Solutions