We present a new wrinkling-based measurement technique for quantifying the viscoelastic properties of confined polymer thin films. This approach utilizes real-time laser-light scattering to observe the kinetics of thermally-induced surface wrinkling, which evolves isothermally as a function of annealing time. Specifically, wrinkling is induced by applying a thermal stress to a polystyrene film ...

Self-organized wrinkling patterns of a liquid crystalline polymer, dictated by the chemico-physically anisotropic nature of surface wettability, are demonstrated in confined geometries. The symmetry of the geometrical constraints of the confinement primarily governs the periodic wrinkling patterns of such a polymer in the wetting region. In a circular geometry, the number of the radial domains ...

This paper deals with two-dimensional plane stress wrinkling model of a plastic annular plate. Based on energy method and the nonlinearity of strain-displacement law, a bifurcation function in polar coordinates is derived analytically. This technique leads to the critical conditions for the onset of the plastic wrinkling of flange during the deep drawing process. To find this solution, the Tres...

This paper reports a simple and flexible method for generating hierarchical patterns from wrinkling instability. Complex features with gradually changing topographies are generated by using the spontaneous wrinkling of a rigid membrane (titanium) on a soft foundation (polystyrene) compressed via the diffusion of a solvent. We show that the morphology of these unreported wrinkled patterns is dir...

* Please send all correspondence to: T. Meinders, University of Twente, Mechanical Engineering Department, Po Box 217, 7500 AE Enschede, The Netherlands. ABSTRACT: Hutchinson approach has been successfully used by a number of researchers in thin sheet metal forming processes for wrinkling prediction. However, Hutchinson approach is limited to regions of the sheet that are free of any contact. T...

Women appear to be at greater risk of developing wrinkles with age than men. To evaluate the effect of pregnancy and menopause on facial wrinkling, a total of 186 Korean women volunteers aged between 20 and 89 years were interviewed for information on menstrual and reproductive factors. An 8-point photographic scale developed for assessing the severity of wrinkles in Asian skin was used. Cumula...

The role of substrate nonlinearity in the stability of wrinkling of thin films bonded to compliant substrates is investigated within the initial post-bifurcation range when wrinkling first emerges. A fully nonlinear neo-Hookean bilayer composed of a thin film on a deep substrate is analysed for a wide range of the film-substrate stiffness ratio, from films that are very stiff compared with the ...

Graphene was dispersed using a tip sonicator and the effect of surfactants were analysed. Sodium Dodecyl Sulphate (SDS) and Polyvinyl Alcohol (PVA) were compared to observe whether or not they had any effect on any de-wrinkling, and secondly whether they aided to achieve better dispersions. There is a huge demand for wrinkle free graphene as this will greatly increase its usefulness in various ...

Various mechanisms have been argued for skin wrinkling, one of the hallmarks of aging. We hypothesize that chronic sympathetic bias is a previously unrecognized mechanism for wrinkling. In the acute setting of water immersion, reversible skin wrinkling is a well-known reflex mediated by the autonomic nervous system. We postulate that skin wrinkling results as a local maladaptive manifestation o...

Tobacco smoke and UV radiation are extrinsic risk factors for accelerated skin ageing. In this study the effects of smoking on wrinkling and ageing were assessed in males living in Northern Finland, where cumulative sun exposure is low. Smoking habits, age and facial wrinkling were estimated from facial photographs of 41 smokers and 48 non-smokers by eight panellists, using a blinded standardiz...