Adaptive dry adhesives with tunable morphology via shape memory elastomeric bilayers

Abstract

Dry adhesives offer appealing advantages such as reusability and clean detachment, yet their performance is fundamentally constrained by the trade-off between adhesion strength and fracture toughness. In this work, we present adaptive bilayer dry adhesives that integrate a thin, compliant elastomeric polydimethylsiloxane (PDMS) surface with a stiff shape memory polymer (SMP) backing layer. While the SMP layer enables shape programming through its rubber-to-glass transition, the PDMS layer suppresses catastrophic adhesive failure and preserves adhesion. Finite element analysis results reveal that the programmed bilayer surface forms extensive interfacial contact with minimal preload, outperforming conventional elastomeric adhesives. Adhesion tests further demonstrate that the bilayer achieves nearly ten-fold higher adhesion compared to PDMS, while maintaining greater detachment toughness relative to SMP, thereby alleviating the inherent trade-off. Moreover, the bilayer’s shape programming capability enables stable and repeatable adhesion to curved surfaces without requiring additional rubber-to-glass transitions. For practical demonstrations, we fabricated an integrated heater-assisted adhesive hook capable of supporting a 2 kg load on diverse wall surfaces, with reversible and reusable operation. This bilayer adhesive strategy provides a generalized design principle to overcome the incompatibility between adhesion and toughness, offering strong potential for applications in soft robotics, wearable systems, and transfer printing.