Switchable adhesion of gecko-inspired hierarchically wedge-mushroom-shaped surface

The outstanding adhesion ability of gecko is mainly attributed to its sophisticated hierarchical adhesive structures. The relationship between structure and function of gecko adhesion has been attracting scientific research interests. However, studies on the effect of the structural hierarchy on the interfacial switchable adhesion remain limited. In the present paper, a gecko toe-inspired hierarchically wedge-mushroom-shaped adhesive is fabricated. The first level is NdFeB particles decorated asymmetrical wedges, mimicking the lamellar structures on gecko toe. The asymmetry of the wedge can guarantee the anisotropic adhesion in different directions. The second level is the mushroom-shaped fibrils on the sloping surface of the wedges, mimicking gecko seta arrays. The mushroomed fibrils can be used to enhance the normal interfacial adhesion. The fabricated hierarchical adhesive possesses the adhesion advantages of both the wedge- and mushroom-shaped structures. Switchable adhesion can be realized both by loading-dragging-pulling (LDP) mode and actuation of external magnetic field. Specially, the switchable adhesion achieved under the control of magnetic field can overcome the drawback of shear induced adhesion limit of normal direction in LDP mode. Furthermore, the fabricated hierarchical adhesive can realize releasing ultra-light objects and highly efficient self-cleaning ability. The hierarchical adhesive inspired by gecko demonstrated in this study may have potential applications in the fields of micro /nano manufacturing and flexible devices.