Adhesive Force Assisted Imprinting of Soft Solid Polymer Films by Flexible Foils

Abstract

We report a simple, rapid, room temperature, pressure-less and large area (approximately cm2) imprinting technique for high fidelity patterning of soft solid polymer films and surfaces like cross-linked polydimethylsiloxane (PDMS) and polyacrylamide (PAA) based hydrogels, both on planar and curved surfaces. The key element of the method is the use of patterned thin flexible foils that readily and rapidly attain a conformal contact with soft (shear modulus < 0.1 MPa) solid surfaces because of adhesive interfacial interactions. The conformal contact is established at all length scales by bending of the foil at scales larger than the feature size, in conjunction with the spontaneous elastic deformations of the surface on the scale of the features. For example, we used the protective aluminum foils of commercial data storage discs, both with or without data stored, for micron and sub-micron pattern transfer. The patterns are made permanent by UV-ozone treatment (for PDMS) or by controlled drying (for hydrogels). Interestingly, elastic contact imprinting of very thin (< 300 nm) films results in about 50% miniaturization of the original foil feature sizes. Complex two dimensional patterns could also be formed even by using a simple one dimensional master by multiple imprinting. The technique can be particularly useful for the bulk nano applications requiring routine fabrication of templates, for example, in the study of confined chemistry phenomena, nanofluidics, bio-MEMS, micro-imprinting, optical coatings and controlled dewetting.

Instability, self-organization and pattern formation in thin soft films

“…[303][304][305][306] The analysis also shows that l is independent of the elastic modulus of the film at the onset of instability as well as the surface tension of the contactor, 303,304 which has been experimentally verified. 311,[330][331][332][333][334] The pre-factor may increase significantly to values higher than 3 in films thinner than E1 mm due to the enhanced effect of surface tension. 311 Nonlinear simulations based on complex energy minimization have been used to predict and understand the mechanism and pathways during the approach and de-bonding of a rigid contactor to/ from a soft interface.…”

Control of morphology in pattern directed dewetting of thin polymer films

“…The patterned substrates were made by Adhesion Assisted Imprinting of crosslinked PDMS (sylgard 184, Dow Chemicals, USA), following methods described elsewhere. [59][60][61] The topography of the patterned substrates are shown in the inset of Fig. 4A (''type 1'' substrate), inset of Fig.…”

Non-equilibrium thermal annealing of a polymer blend in bilayer settings for complex micro/nano-patterning

“…A structured aluminium foil was peeled off from a compact disk (CD) to use it as a flexible stamp with alternate lines of grooves and crests with periodicity, width and height of about 1.6 μm, 800 nm and 120 nm respectively. 51 This flexible CD foil was carefully placed on the thin RCP film prepared and sandwiched between two glass slides with the help of a pair of binder clips to induce uniform pressure. The whole set up then heated over 120 °C for 12 h to induce capillary force lithography (CFL).…”