The Parametric Study of Focused Laser-Induced Marangoni Dewetting for Patterning Polymer Thin Films (original) (raw)

Ultrathin (< 100 nm) unstable polymer films exposed to a solvent vapor dewet by the growth of surface instability, the wavelength (λ) of which depends on the film thickness (hf). While dewetting of a flat polymer thin film results in random structures, we show that dewetting of a pre-patterned film results in a myriad of ordered meso-scale morphologies under specific conditions. Such a film undergoes rupture over the thinnest parts when the initial local thickness of these zones (hrm) is lower than a limiting thickness hlim  10 nm. Additionally, the width of the pattern grooves (ls) must be wider than λs corresponding to a flat film having thickness of hrm for pattern directed dewetting to take place over surface tension induced flattening. We first present an experimentally obtained morphology phase diagram that captures the conditions where a transition from surface tension induced flattening to pattern directed rupture takes place. Subsequently, we show the versatility of thi...

Direct laser interference patterning (DLIP) involves the formation of patterns of light intensity using coherent laser light beams that interfere between them. Light on the ultraviolet (<350 nm) and NIR (800–2000 nm) is absorbed in chromophores present in the polymer structure or in loaded absorbing species (dyes, polymers, nanoparticles). The absorbed light induces photothermal/photochemical processes, which alter permanently the topography of the polymer surface. The success of DLIP at different wavelengths is discussed in relation to the optical/thermal properties of the polymers and previous data on laser ablation of polymers. The size of the pattern is related directly to the wavelength of the light and inversely to the sine of the angle between beams and the refractive index of the external medium. In that way, nanometric structures (<100 nm) could be produced. Since the patterning occurs in a single short pulse (<10 ns), large surfaces can be modified. Both bacterial...

The instability, dynamics and morphological transitions of patterns in thin liquid films on periodic striped surfaces (consisting of alternating less and more wettable stripes) are investigated based on 3-D nonlinear simulations that account for the inter-site hydrodynamic and surface-energetic interactions. The film breakup is suppressed on some potentially destabilizing nonwettable sites when their spacing is below a characteristic lengthscale of the instability, the upper bound for which is close to the spinodal lengthscale. The thin film pattern replicates the substrate surface energy pattern closely only when, (a) the periodicity of substrate pattern matches closely with the characteristic lengthscale, and (b) the stripe-width is within a range bounded by a lower critical length, below which no heterogeneous rupture occurs, and an upper transition length above which complex morphological features bearing little resemblance to the substrate pattern are formed.