Figure 7.

Bioinspired or biomimetic adhesives. (a) Adhesion hydrogel with water-proof adhesion ability inspired from the features of clingfish adhesion discs: hexagonal facets separated by grooves. (Reprinted from ref. [63] with permission from John Wiley & Sons, Inc.) (b) Adhesion patch inspired from the suction cups of an octopus: negative pressure generated by the inner hollow structure. (Reprinted from ref. [162] with permission from Springer Nature Limited.) (c) Bioinspired wet adhesion patch using hierarchical hexagonal structures: hexagonal structures (pads of tree frog) and protuberances with a hollow structure (suction cup of octopus vulgaris tentacle). (Reprinted from ref. [165] with permission from John Wiley & Sons, Inc.) (d) Adhesion patch made by nanopile interlocking inspired from the stretching of fractal roots into soft soil (Reprinted from ref. [166] with permission from John Wiley & Sons, Inc.)