Tunable nanoparticle stripe patterns at inclined surfaces

Periodic assemblies of nanoparticles are central to surface patterning, with applications in biosensing, energy conversion, and nanofabrication. Evaporation of colloidal droplets on solid substrates provides a simple yet effective route to achieve such assemblies. This work demonstrates tunable periodic stripe formation from evaporating gold nanoparticle suspensions on inclined substrates through stick-slip dynamics of the three-phase contact line. Variation in nanoparticle concentration and substrate inclination alter the balance of interfacial and gravitational forces, producing multiple stick-slip events that generate periodic stripes. Stripe density shows a non-monotonic variation with inclination angle, while inter-stripe spacing remains relatively invariant to inclination. The spacing is governed by local capillary-pinning interactions and can be tuned through changes in nanoparticle or surfactant concentration. These results highlight the complex interplay of gravitational and interfacial forces in directing periodic nanoparticle assembly and establish a simple and adaptable framework for tunable nano/microscale surface patterning.