Direct Laser Interference Patterning of Functional Metal Surfaces: From Written Geometry to Functional Interfaces
Direct laser interference patterning (DLIP) generates periodic micro- and nanoscale structures with increasing precision and throughput, yet similar geometries can produce fundamentally different functional responses. This review examines why morphology alone cannot predict friction, wetting and ice adhesion, bacterial response, cell behaviour, optical performance or electrochemical and photovoltaic function. DLIP is treated as a model system in which the optically prescribed geometry can be distinguished from the interface realised during processing. The written period is separated from relief depth, aspect ratio, hierarchical topography, surface chemistry, ageing and process history. Functional response is interpreted as a two-stage process: geometry creates the opportunity for interaction with an external agent, while the realised interface determines how that interaction becomes measurable performance under a specific interfacial state. A curated, metals-centred evidence base spanning tribology, wetting and anti-icing, antibacterial and biomedical surfaces, optics, electrochemistry, energy devices and manufacturing shows that period-depth coordinates alone rarely predict function across domains. Geometry remains highly transferable in optical systems and controlled mechanical contacts, whereas biological, state-dependent and device-level functions also depend on surface state, operating conditions and system architecture. The framework reconciles conflicting observations and identifies which variables are transferable and which remain context-dependent. Predictive DLIP surface engineering therefore requires identification of the interacting agent, separation of written geometry from the realised interface, isolation of variables governing interfacial coupling and evaluation through direct, mechanism-specific endpoints.