Continuous directional water transport on the peristome surface of Nepenthes alata

Abstract

Numerous natural systems contain surfaces or threads that enable directional water transport. This behaviour is usually ascribed to hierarchical structural features at the microscale and nanoscale, with gradients in surface energy and gradients in Laplace pressure thought to be the main driving forces. Here we study the prey-trapping pitcher organs of the carnivorous plant Nepenthes alata. We find that continuous, directional water transport occurs on the surface of the 'peristome'--the rim of the pitcher--because of its multiscale structure, which optimizes and enhances capillary rise in the transport direction, and prevents backflow by pinning in place any water front that is moving in the reverse direction. This results not only in unidirectional flow despite the absence of any surface-energy gradient, but also in a transport speed that is much higher than previously thought. We anticipate that the basic 'design' principles underlying this behaviour could be used to develop artificial fluid-transport systems with practical applications.

Surfaces Inspired by the Nepenthes Peristome for Unidirectional Liquid Transport

“…A recent study demonstrated that there is a unidirectional water-transport process after a water droplet is dropped on the peristome surface. [10] The unidirectional transport enables the droplet to form a uniform liquid film, which contributes to the slippery function. This unique fluid flow is caused by the multiscale structure.…”

“…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.…”

Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

“…Inspired by nature, [1][2][3][4][5][6][7][8][9][10][11][12][13][14] the special wettability of material surfaces, which is engineered via synergistic utilization of microscale surface structures and surface chemistry has been one of the most active research fields, and it can play a key role in addressing problems related to energy, environment, resources, and health. Efforts in the past decades have explored controllable fabrication, functionality, and performance optimization of bionic superhydrophobic surfaces with a contact angle above 150°, and they have resulted in technological innovations such as self-cleaning, drag-reduction, anticorrosion, antifogging, antifreezing and oil-water separation.…”

External‐Field‐Induced Gradient Wetting for Controllable Liquid Transport: From Movement on the Surface to Penetration into the Surface

“…[42][43][44][45][46][47][48][49][50][51] For a droplet on a solid or liquid surface, there is no driving force for droplet motion in the equilibrium state. When a wettability gradient is generated on the surface (Figure 2), imbalanced forces can be produced on the two opposite sides of the droplet.…”