Gecko-inspired soft actuators for wafer handling via overcuring-induced anisotropic microstructures in DLP 3D printing

The anisotropic setae structures of geckos demonstrate a natural anisotropic response to external forces, thereby enabling rapid and repeated attachment and detachment. Considering this biological mechanism, this study proposes an innovative process that harnesses the overcuring of resins in digital light processing (DLP) 3D printing to emulate setae structures. The proposed method facilitates the spontaneous fabrication of anisotropic shapes from isotropically modeled geometries. Furthermore, it reduces the number of hierarchical structures typically produced in conventional 3D printing and creates smooth surfaces, thereby enhancing the structural stability for directional adhesion and detachment. The anisotropic structures were processed into functional surfaces through a double-casting method, exhibiting an adhesive strength akin to that of gecko-setae structures while maintaining easy detachment capabilities. Finally, a simple mechanical module was fabricated to directly demonstrate the detachment effect. This study introduces a novel approach to DLP printing for fabricating enhanced anisotropic structures that can be seamlessly integrated with existing 3D printing techniques. By strategically utilizing overcuring, a phenomenon often perceived as a limitation, this study demonstrated its potential to expand the boundaries of next-generation 3D printing technologies.