Water transport mechanism through open capillaries analyzed by direct surface modifications on biological surfaces

Abstract

Some small animals only use water transport mechanisms passively driven by surface energies. However, little is known about passive water transport mechanisms because it is difficult to measure the wettability of microstructures in small areas and determine the chemistry of biological surfaces. Herein, we developed to directly analyse the structural effects of wettability of chemically modified biological surfaces by using a nanoliter volume water droplet and a hi-speed video system. The wharf roach Ligia exotica transports water only by using open capillaries in its legs containing hair- and paddle-like microstructures. The structural effects of legs chemically modified with a self-assembled monolayer were analysed, so that the wharf roach has a smart water transport system passively driven by differences of wettability between the microstructures. We anticipate that this passive water transport mechanism may inspire novel biomimetic fluid manipulations with or without a gravitational field.

Surfaces Inspired by the Nepenthes Peristome for Unidirectional Liquid Transport

“…Many natural systems have evolved into functional surfaces to achieve water transport for survival, [1][2][3][4][5][6][7][8][9][10] for example, the back of desert beetles, [1] shorebird beaks, [3] spider silk, [5] and cactus spines. [6] Without energy input, these biological surfaces can harness the movement of water through their unique structural features and chemical composition, [11][12][13] which gives inspiration for designing and fabricating functional surfaces and materials with wide applications in fields including antifogging and fog-collection, [14][15][16] microfluidic devices, [17][18][19][20][21] lubrication, [22,23] and liquid transport.…”

Passive water collection with the integument: mechanisms and their biomimetic potential

“…Capillary liquid transport can take place in small cavities, such as tubes, ridges or channels, where the capillary forces dominate other major contributing forces such as viscosity, friction or gravitational force (Berthier and Silberzan, 2010). Corresponding surface structures can be found in the granular skin of some toads and elephants (Lillywhite and Licht, 1974;Lillywhite and Stein, 1987), surface channels of moisture-harvesting lizards (Gans et al, 1982;Withers, 1993;Veselý and Modrý, 2002;Sherbrooke et al, 2007;Comanns et al, 2015), flat bugs and wharf roaches (Hoese, 1981;Horiguchi et al, 2007;Ishii et al, 2013), and cavities between feather structures of sandgrouse (Rijke, 1972;Joubert and MacLean, 1973;Rijke and Jesser, 2011). In the case of moisture-harvesting lizards, transportation in channels avoids wetting much of the body surface and hence losing volume by evaporation from a larger area (Comanns et al, 2011;Yenmisȩ t al., 2015).…”

“…Further examination has revealed more detail: hair-and paddle-like microstructures on two neighboured legs (i.e. pereiopods VI and VII) collect and transport the adhered water; the water is then transported further along the swimming limbs ( pleopods) and to the hindgut, near the anus, for uptake by absorption (Horiguchi et al, 2007;Ishii et al, 2013). Collected water also establishes a water film on the integument and evaporation is regularly used for thermoregulation (Hoese, 1981).…”

Length Scale Selects Directionality of Droplets on Vibrating Pillar Ratchet

“…[ 4 ] These biological inspired systems enable droplet motion via capillary phenomena, [10][11][12] mechanical vibrations, [ 13 ] chemical patterning, [14][15][16] and gradients of texture. [ 17,18 ] In addition, deterministically designed systems provide a robust, manufacturable platform that can even take advantage of unique scenarios not found in nature, such as the Leidenfrost effect [ 19 ] or reversible electrowetting.…”

“…Controlling droplet motion is of signifi cant interest for a broad range of applications including microfl uidics, [ 1,2 ] water harvesting, [ 3,4 ] printing, [ 5 ] and chemical sensing. [ 6 ] The use of asymmetrically structured surfaces, commonly referred to as ratchets, has been widely investigated as a means to control multiphase fl uid fl ows, in particular droplet motion.…”