Highly oriented tunable wrinkling in polymer bilayer films confined with a soft mold induced by water vapor

Abstract

The authors report the formation of highly oriented wrinkling on the surface of the bilayer [polystyrene (PS)/poly(vinyl pyrrolidone) (PVP)] confined by a polydimethylsiloxane (PDMS) mold in a water vapor environment. When PVP is subjected to water vapor, the polymer loses its mechanical rigidity and changes to a viscous state, which leads to a dramatic change in Young's modulus. This change generates the amount of strain in the bilayer to induce the wrinkling. With a shape-controlled mold, they can get the ordered wrinkles perfectly perpendicular or leaned 45 degrees to the channel orientation of the mold because the orientation of the resultant force changes with the process of water diffusion which drives the surface to form the wrinkling. Additionally, they can get much smaller wrinkles than the stripe spacing of PDMS mold about one order. The wrinkle period changes with the power index of about 0.5 for various values of the multiplication product of the film thicknesses of the two layers, namely, lambda approximately (h(PS)h(PVP))(1/2).

Active and responsive polymer surfaces

“…Qian et al 73 took advantage of solvent vapor instead of changing temperature to prepare highly oriented wrinkles. Water vapor induced wrinkles in a rigid-PS-viscous-poly(vinyl pyrrolidone)(PVP) bilayer confined by a soft mold, realizing an ordered pattern in the solvent state.…”

“…Copyright 1999 American Institute of Physics. (Right): Optical microscope images of various wrinkles in different regions on the surface of the PS/PVP bilayer induced by water vapor in a PDMS mold 73. Copyright 2007 American Institute of Physics.…”

Wrinkling Polymers for Surface Structure Control and Functionality

“…[6][7][8] At an increasing rate, over the past decade researchers have exploited the elastic instability of surface wrinkling as a mechanism for controlling polymer surface morphology, enabling technical advances in areas from enhanced metrology for materials properties to flexible electronics. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] However, unleashing the full potential of surface wrinkling requires a fundamental understanding of the material properties that define kinetic and equilibrium structures.…”

Wrinkling Measurement of the Mechanical Properties of Drying Salt Thin Films

“…The analysis of wrinkling topographies has also been shown to provide a powerful tool for the mechanical characterisation of thin and ultra-thin polymeric, composite and metallic supported thin films 2,7,16,17,18 .…”

“…Spontaneous surface wrinkling of laminate films can occur as a result of mechanical stress 3,4,5,6 , expansion and contraction associated thermal deposition, or during solvent evaporation and shrinkage 7,8,9,10,11 , and is often undesirable 7,8,11,12,13,14,15 . The analysis of wrinkling topographies has also been shown to provide a powerful tool for the mechanical characterisation of thin and ultra-thin polymeric, composite and metallic supported thin films 2,7,16,17,18 .…”