Capillary Rise on Legs of a Small Animal and on Artificially Textured Surfaces Mimicking Them

Abstract

The wharf roach Ligia exotica is a small animal that lives by the sea and absorbs water from the sea through its legs by virtue of a remarkable array of small blades of micron scale. We find that the imbibition dynamics on the legs is rather complex on a microscopic scale, but on a macroscopic scale the imbibition length seems to simply scale linearly with elapsed time. This unusual dynamics of imbibition, which usually slows down with time, is advantageous for long-distance water transport and results from repetition of unit dynamics. Inspired by the remarkable features, we study artificially textured surfaces mimicking the structure on the legs of the animal. Unlike the case of the wharf roach, the linear dynamics were not reproduced on the artificial surfaces, which may result from more subtle features on the real legs that are not faithfully reflected on the artificial surfaces. Instead, the nonlinear dynamics revealed that hybrid structures on the artificial surfaces speed up the water transport compared with non-hybrid ones. In addition, the dynamics on the artificial surfaces turn out to be well described by a composite theory developed here, with the theory giving useful guiding principles for designing hybrid textured surfaces for rapid imbibition and elucidating physical advantages of the microscopic design on the legs.

Towards combinatorial mixing devices without any pumps by open-capillary channels: fundamentals and applications

“…In fact, two simple scaling regimes for the coefficient have been identified 33 depending on the ratio of the pillar height to the pillar distance. The different dynamics z ~ t 1/3 has also been found in different situations 36 37 38 , together with other slowing-down dynamics observed for imbibition of papers 39 40 and an unusual linear dynamics found for imbibition on the surface of legs of a certain animal 5 .…”

“…1a-b ) 36 37 , but the geometries are rather different). In addition, recently, for another type of open capillary found on the leg of the wharf roach Ligia exotica , a small animal living by the sea, yet another scaling law, z ~ t , is found 5 (see Fig. 1f ).…”

“…1f and Ref. 5 ). Since such scaling laws are highly useful for the development of the device for the transport of a small amount of liquid, studies on the imbibition of open capillary is indispensable not only from a fundamental viewpoint but also from a practical viewpoint.…”

“…Micropatterned surfaces are ubiquitous in nature and found, for example, on the surface of plants 1 , insects 2 3 , and animals 4 5 . Partly because of the inspiration from such natural structures, extensive studies on micropatterned surfaces 6 have been devoted for understanding and controlling specific wetting properties such as superhydrophobicity 7 and leophobicity 8 .…”

Scaling crossover in thin-film drag dynamics of fluid drops in the Hele-Shaw cell

“…In this respect, the present problem is closely related to the dynamics governed by thin film dissipation such as the imbibition of textured surfaces. [33][34][35][36][37][38] In this sense, our problem is quasi two-dimensional, although the geometry of the Hele-Shaw cell is often associated with a purely two-dimensional problem. ρ in depends on its kinematic viscosity ν in only slightly (see the details for Methods).…”