The Texas horned lizard (Iguanidae: Phrynosoma cornutum) inhabiting arid regions utilizes its dorsal integument to access water sources. Thanks to its highly-evolved integument consisting of microsized overlapping scales showing water repellency and nanosized capillary channels showing water affinity, water can be directed preferentially towards the lizard’s snout, achieving the power-free transportation.

Under the inspiration of lizard’s integument, a variety of artificial surfaces with power-free water transportation capacity have been developed because of their wide applications in fog collection, membrane filtration, biomedical testing, and hydropower generation.

In a recent study published in Chemical Engineering Journal, Dr. LIU Ziai and Prof. LI Wei from Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS), collaborating with Prof. SONG Jinlong from Dalian University of Technology and LIU Hang from Mindray Bio-Medical Electronics Co., Ltd, proposed a bioinspired surface for power-free water transportation.

Two-step nanosecond laser ablation and fluoroalkyl silane modification were employed to fabricate a patterned super-wettability surface with a superhydrophilic serial-wedge-shaped channel embedded in a superhydrophobic panel, which is based on the inspiration of P. cornutum’s dorsal integument. Water contact angles on the superhydrophilic channel and the superhydrophobic panel were ~0° and ~157°, respectively.

The transportation capacities of the channels with different configuration parameters were explored and the maximum speed of droplet on the channel with the optimum configuration parameters was ~30.4mm/s. Moreover, some channels with complicated configurations were also fabricated and the power-free water transportation could be achieved conveniently on the horizontal long-distance straight channel, the horizontal curving channel, and the inclined straight channel.

To alleviate the pinning effect of the channel boundaries to the transportation process, an optimization strategy was subsequently promoted to adjust the configuration of the channel from an angular structure to a smooth structure. A higher speed of ~31.8mm/s were obtained on the optimized channel, revealing a 5% improvement.

This study provides more possibilities for the development of water harvesting platforms and heat transfer equipment, and will open up new avenues for next-generation high-performance fluid transportation systems.

Figure 1. Power-free water transportation on natural and artificial surfaces. (a) Digital images of Phrynosoma cornutum. (b) Schematic and digital image of the patterned super-wettability surface. (c) Transportation on channels with different configurations.