Phragmites Communis Leaves with Anisotropy, Superhydrophobicity and Self-Cleaning Effect and Biomimetic Polydimethylsiloxane (PDMS) Replicas

Phragmites communis leaf (PCL) is anisotropic, superhydrophobic and shows a self-cleaning effect. The water contact angle (WCA) values along the vertical and parallel vein directions on PCL are 153 degrees +/- 2 degrees and 148 degrees +/- 2 degrees, respectively. In contrast, the water sliding angle (WSA) values along the vertical and parallel vein directions for PCL are 12 degrees +/- 2 degrees and 7 degrees +/- 2 degrees, respectively. The epidermal wax makes the leaves intrinsically hydrophobic. The microstructure of the PCL surface shows sub-millimetre-, micron- and nanometre-scale structures. The sub-millimetre ridge structure is the main reason for the anisotropy of the leaves. The micron-scale papillae structure has a strong hydrophobic enhancement effect, and the nanoscale sheet structure is the key factor in achieving a stable Cassie state, as well as superhydrophobicity and self-cleaning activities. PCL-like polydimethylsiloxane (PDMS) samples fabricated by template transfer technology exhibited the sub-millimetre ridge structure and micron-scale papillae from the natural PCL; they also show obvious anisotropy and strong hydrophobicity and have a certain self-cleaning effect. The WCA and WSA values along the vertical and parallel vein directions on PCL are 146 degrees +/- 2 degrees, 23 degrees +/- 2 degrees, 142 degrees +/- 2 degrees and 19 degrees +/- 2 degrees, respectively. The preparation of a biomimetic PCL surface has broad application prospects in micro-fluidic control and the non-destructive transmission of liquids.