Reversible Microadhesives with Good Adhesion Anisotropy via Dual-Gradient Modulus Constructing

Bioinspired microadhesives can generate strong adhesion at the interface through van der Waals forces, demonstrating promising potential applications across various fields. However, the inherent conflicts between microstructural stability and compliance, as well as strong adhesion and easy detachment, significantly hinder the development and practical applications of microadhesives. In this work, wedged microadhesives (WMs) of dual-gradient modulus are fabricated via magnetically assisted soft-molding. The dual-gradient modulus WMs exhibit a maximum shear adhesion performance of 4.9 N cm^-2 and a minimum normal adhesion performance of 0.13 N cm^-2 under the same preload, achieving an excellent anisotropy ratio (AR) of up to 37.7. The dual-gradient modulus generates a greater modulus gradient difference, with the low modulus facilitating to maintain well-conformal contact, while the high modulus enhances the shear adhesion and normal detachment capabilities, which simultaneously improve the long-term stability. Additionally, a quadruped gripping mechanism is designed and exhibited stable grasping and on-demand rapid release when integrated with the WMs, demonstrating an excellent anisotropic adhesion performance. The dual-gradient modulus WMs provide a valuable solution for designing microadhesives that exhibit both structural stability and compliance, along with strong adhesion and easy detachment. These findings will greatly benefit the applications of reversible microadhesives in on-orbit servicing technology.