Asymmetric fractures enabled fracture diodes via dry patterning

Abstract

Combining interfacial mechanical phenomena with photolithography presents a promising frontier for developing advanced microfabrication strategies. However, achieving precise control over interfacial adhesion during such processes remains a critical challenge. In this work, we introduce a novel outline-defined asymmetric fracture lithographic dry-patterning method for the deterministic control of interfacial adhesion in photoresist microstructures. This approach leverages geometrically designed asymmetric structures (fracture diodes) to dictate the propagation direction of fractures during mechanical peeling. Inspired by mechanical metamaterials, these fracture diodes enable unidirectional fracture propagation by creating a stress gradient, requiring significantly different stresses for fracture initiation in opposing directions. We demonstrate large-area fabrication of these patterns on 6-inch wafers with 100% yield. By designing and peeling anisotropic fracture diode structures with varying orientations, we achieved controlled and quantifiable peeling percentages, directly demonstrating fracture anisotropy. Finite element analysis (FEA) confirms the underlying mechanism that the fracture diode effect arises from fracture-related stress variations dictated by the structural asymmetry. Exploiting this directional fracture control, we implement high-security applications that revealed direction-specific decryption patterns only when peeled in the correct orientation, and color anti-counterfeiting patterns based on Fabry–Pérot cavity effects created by photoresist thickness modulation. These functionalities converge into peelable labels offering continuous, irreplicable security levels, positioning this fracture diode-enabled dry-patterning technique as a powerful platform for advanced anti-counterfeiting and surface nanotechnology.