Fig. 3From: Tree frog attachment: mechanisms, challenges, and perspectivesA Schematic representation of capillary adhesion between a toe pad (green) and a hydrophilic substrate caused by the formation of a mucus meniscus (blue). Left inset: Capillary adhesion between two flat, solid plates. Right inset: Capillary adhesion between a solid sphere and a flat, solid plate. B Hypothesised changes in wetting state with an increase in substrate roughness or pad-substrate gap width [97]. dg gap width, F⊥,cap capillary adhesion, R sphere radius, Rmer, Razi meridional and azimuthal radius of meniscus curvature, β filling angle, γ mucus surface tension, ϕ contact angle. B modified after [97]. Printed with permissionBack to article page