Well-ordered “tooth-shaped” silver-microstructures on poly(methyl methacrylate) patterned by laser writing

Thermocapillary approaches to the deliberate patterning of polymers

“…Despite these and other investigations in metals and later silicon, thermocapillary dewetting of polymers by LSA was only investigated in the past decade. The first method to accomplish this was developed by Lyutakov and coworkers . In their approach, they applied a diffraction limited 415 CW focused spot to heat a dye doped polymer films of ∼1 of PS and PMMA .…”

“…(a)]. A similar direct write method would also be adopted by Lyutakov and coworkers, instead using highly dye doped (4 wt %) polymer thin films at rates of up to 10 mm/s …”

“…Lyutakov, for example, overlapped orthogonal grating structures to create square lattices of bifurcated heights and, with silver‐coated polymers, anisotropic silver “tooth” structures [Fig. (b)] . Additionally, by placing the high‐speed lines at close proximity, regular 2D structures were generated, including, by more complex defocused and off angle exposure, regular hexagonal gratings .…”

Thermocapillary Multidewetting of Thin Films

“…For example, when the laser writing occurred too quickly for the material to dewet, periodic patterns would appear along written lines [5]. Similar effects were observed when bilayers were employed with low mobility materials on top and high mobility materials underneath, such as high molecular weight (MW) polymer on low MW [3] or silver on polymer [4]. In this work, we instead explore the potential to sequentially pattern materials with different softening points, allowing for the individual dewetting, or non-dewetting, of materials in multilayers.…”

“…Because is negative in most materials, subjecting films to concentrated hot spots produces a shear force radially down the thermal gradient. In this way, focused laser spike (FLaSk) excitation with continuous wave lasers has been used to apply thermocapillary shear to polymer thin films and can result in either dewetting [2][3][4][5] or shear-induced reordering [6,7] by inducing thermal gradients of up to 1000 K/μm. Past work has explored FLaSk dewetting as a direct write technique and has explored the effects of different molecular weights [3], thicknesses [2,3], and writing speeds [5], with the conclusion that film mobility, as expressed by the temperature dependent viscosity, has the largest effect on resulting patterns of any patterns.…”