A capillary structure for passive, directional fluid transport includes a capillary having a forward direction and a backward direction, the capillary including first and second capillary units each having a sequence of capillary components including a connective section in fluid communication with a diverging section, the diverging section having a forward side and dimensions inducing a concave meniscus in the forward direction, wherein the connective section of the second capillary unit is connected to the forward side of the diverging section of the first capillary unit to form at least one transition section, and wherein a change in the dimensions in the transition section induces in the backward direction a convex liquid meniscus or a straight liquid meniscus with an infinite radius of curvature.