Programmable Nanopatterns by Controlled Debonding of Soft Elastic Films.

We report a facile patterning technique capable of creating nanostructures with different feature heights (hS ), periodicities (λS ), aspect ratios (AR ), and duty ratios (DR ), using a single grating stamp with fixed feature height hP and periodicity λP . The proposed method relies on controlling the extent of debonding and morphology of the contact instability features, when a rigid patterned stamp is gradually debonded from a soft elastic film to which it was in initial conformal contact. Depending on whether the instability wavelength (λF scales with the film thickness hF as λF ≈ 3hF ) and the periodicity of the stamp feature (λP ) are commensurate or not, it is possible to obtain features along each stamp protrusion when λF ≈ λP or patterns that span several stripes of the stamp when λF > λP . In both cases, the patterns fabricated during debonding are taller than the original stamp features (hS > hP ). We show that hS can be modulated by controlling the extent of debonding as well as the shear modulus of the film (μ). Additionally, when λF > λP , progressive debonding leads to the gradual peeling of replicated features, which, in turn, allows possible tuning of the duty ratio (DR ) of the patterns. Finally we show that by the simultaneous modulation of AR , DR , and hS , it becomes possible to create surfaces with controlled wettability.