Controlled Adhesion Anisotropy between Two Rectangular Grooved Surfaces

Abstract Friction or adhesion anisotropy is a key indicator in surface physics and chemistry. Compared with friction anisotropy, a few studies focus on adhesion anisotropy, which has a profound potential in guiding the application of biomimetic adhesive surfaces. The adhesion anisotropy coefficients (the ratio of maximum adhesion to the minimum one) of the reported biomimetic surfaces are mostly less than 20. In this study, a simple strategy is proposed to achieve a significant adhesion anisotropy between two same rectangular grooved (RG) polymer surfaces. The corresponding adhesion force can be varied by over two orders of magnitude by changing the aligning state, far beyond the previously reported adhesion anisotropy coefficient. As expected, the strongest adhesion appears when the grooves are parallel to each other, while the weakest adhesion exists at a perpendicular crossing contact. The complex alignment between two same micro‐RG surfaces is accurately accomplished by using moiré patterns. Applying a lateral shearing at a matching state can further enhance the adhesion due to the side‐wall friction. This apparent adhesion anisotropy has a great potential to be used in novel flexible dry adhesive grippers or connectors.