Topological Structuring of Adhesive Layers to Enhance Resistance against Interfacial Fracture

The reliable bonding of dissimilar materials is crucial for lightweighting and energy saving. However, their interface is often susceptible to fracture, impeding the widespread adoption of composites. While tough adhesion relying only on intermolecular interactions has been effective for specific adherends, fracture strength is significantly impaired depending on the adhesive selection. Alternatively, it is also widely used to improve the bonding strength through mechanical interlocking (anchor effect) via surface structuring. However, this approach has problems in energy consumption and environmental considerations associated with etching and surface cleaning procedures. Here, we introduce an alternative/hybrid approach that combines chemical affinity with structural interlocking. We produce a porous layer strongly interacting with one adherend using a solution-based technique. This porous architecture templates a robust mechanical interlock with the other adherend, without using conventional adhesives. By tuning pore geometry, this method enables a detachment strength of over 7 MPa, showing significant improvement compared with unstructured interfaces. Experiments and simulations reveal that the fracture toughness stems from a stiffness difference within the interlocked structure, suppressing crack propagation. This structural design strategy offers a rational route to engineering durable interfaces, enabling advanced composites of various materials.