Effect of Thermal Reflow on Microstructural Morphology and Contact Mechanics in the Photo-Lithographic Fabrication of Biomimetic Adhesive Materials.

Abstract

Bionic adhesive materials with 3D complex micro/nanostructures have several advantages of low preload, strong adhesion, switchable adhesion, etc. As the primary high-precision fabrication method for such materials, lithography is inherently limited by its 2D processing capabilities. Achieving complex 3D morphologies typically requires auxiliary processes, such as dipping and double-sided separate UV exposures, which increase both the complexity and limitations of the fabrication process. In this work, an efficient dimensional regulation method-the photo-lithographic thermal reflow is proposed. The technique utilizes the intrinsic properties of photoresist materials, introducing thermal energy to transform microstructures from 2D to 3D. Mushroom-shaped morphology is taken as an example to fabricate bionic adhesive materials. The fabricated mushroom-shaped micropillar arrays exhibit different tendencies in adhesion force, friction, reversible adhesion, and repeatability, demonstrating the precise tunability of the micropillar geometry. The optimized mushroom-shaped adhesive material not only exhibits the adhesion force of up to 12.26 N on the silicon surface (superior to that of a single foot of gecko (10 N)) but also shows superior friction, easy peeling and high durability. The result demonstrates that this method enables rapid and efficient regulation of 3D morphology and provides a novel approach for the fabrication of complex micro/nanostructure.