Wrinkle formation

Fig. 2 Schematic depiction of wrinkle formation of a hard film in adhesive contact with a softer elastomeric substrate. The wavelength X is mainly determined by film thickness h and elastic properties of film and substrate. The amplitude A can be controlled by the strain...

The theoretical concept explained above is rather universal. It has few restrictions in terms of materials used for wrinkle formation. The main requirement is that the Young s modulus of the film is large as compared to the substrate elastomer. In addition, if micron- and sub-micron wavelengths are desired, the film thickness should be controllable on the nanoscale. In most of the work, polydimethylsiloxane (PDMS) was used as elastomeric substrate. Experimentally, both transient wrinkles, which only exist when macroscopic strains are applied, and permanent wrinkles, which remain in the absence of macroscopic strains, can be produced. Both cases are illustrated in Figs. 3 and 4 for the simplest situation of a uniaxial deformation. 

Historically, wrinkles on PDMS were first observed upon metal evaporation. Martin and coworkers reported wrinkle formation by evaporation of aluminum onto PDMS [39], which was first not followed further. The potential of metal evaporation onto PDMS for structuring purposes was recognized only 17 years later by Bowden [15]. In these experiments, the metal was coated onto thermally expanded PDMS. Returning the sample to room temperature causes thermal shrinkage of the PDMS and consequently wrinkling of the top layer. Chen and coworkers have theoretically shown that the herringbone-type pattern observed under these conditions... 

McCormick, S. Materials science - Exploiting wrinkle formation. Science 317(5838), 605-606 (2007)... 

The main idea behind this new approach consists of thermoforming a thermoplastic or polyurethane film as part of the moulding sequence. By using a vacuum effect, this film adheres perfectly and smoothly to the mould cavity, without any creases or wrinkle formation. The mould is equipped with a dedicated frame device, specifically designed to hold the film. A heating system ensures that the film reaches the desired temperature prior to the thermoforming phase and subsequent injection of polyurethane into the mould. 

Son ED, Choi GH, Kim H, Lee B, Chang IS, Hwang JS.Alpha-ketoglutarate stimulates procoUagen production in cultured human dermal fibroblasts, and decreases UVB-induced wrinkle formation following topical application on the dorsal skin of hairless mice. Biol Pharm Bull 2007 30 1395-9. 

Simulation should be able to account for drapability of the fiber preform to investigate any wrinkle formation and also to predict the permeability of the sheared fiber bundles. The permeabilities of the elements should be modified accordingly to accurately reflect the flow physics. ... 

Inui M, Ooe M, Fuji K, Matsunaka H, Yoshida M, Ichihashi M (2008) Mechanisms of inhibitory effects of CoQlO on UVB-induced wrinkle formation in vitro and in vivo. Biofactors 32 237-243 Johnson A, Gin P, Marbois BN, Hsieh EJ, Wu M, Banos MH, Qarke CF, Tzagoloff A (2005) COQ9, a new gene required for the biosynthesis of coenzyme Q in Saccharomyces cerevisiae. J Biol Chem 280 31397-31404... 

On the other hand, phlorotannins have been revealed as potential inhibitors of wrinkle formation as a result of suppressing MMPs. For the first time, Kim and colleagues have reported a detailed study of the inhibitory effect of phlorotannins from E. cava on MMP-2... 

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