The optical diffusion of transmitted or refl ected light via a deformable wrinkled surface with a periodicity in the range of hundreds of micrometers is studied. Without strain, the sample shows no wrinkles and no optical diffusion. With uniaxial strain, the surface shows aligned wrinkles and anisotropically diffuses incident light in a manner that depends on the degree of applied strain. The relationship between the sinusoidal microstructure and the diffused state is successfully explained in the context of geometric optics. The present system can be used as a mechanically tunable optical diffuser.

PACS 73.61. Ga, 81.15.Cd, 84.60.Jt Polycrystalline n-ZnO/p-Cu 2 O heterojunctions were fabricated by reactive sputtering for photovoltaic applications. Although electrical rectification was not reproducibly obtained in the as-grown samples, rectification was observed in the samples fabricated with cyanide treated Cu 2 O. We have previously shown that cyanide treatment has an effective role in passivation of defects in Cu 2 O, in analogy to hydrogen passivation. It is, therefore, believed that the observed improvement in the electrical rectification of the ZnO/Cu 2 O heterojunctions is attributable to the defect passivation near the hetero-interface. The effectiveness of the cyanide treatment and the importance of defect passivation in ZnO/Cu 2 O heterojunctions are presented.

Wrinkling of a soft elastomer surface capped by a relatively hard thin film or modified by some physical treatments to induce hardening has been widely studied for applications in fields such as low-cost micro-fabrication, optics and tribology. Here we show that a biaxial textile sheet embedded on the surface of an elastomer buckles and selectively forms anisotropic wrinkles when experiencing a compressive strain in the fibre axial direction. The wrinkles also possess a fine surface structure that originates from the periodic structure of the biaxial textile sheet. Depending on whether the surface is wrinkled or not, the unique frictional property due to which the friction on wrinkles significantly decreases by a factor of less than 0.1 because of the localized contact regions on the protrusions originating from the textile structure is shown.

ABSTRACT:We report on a periodic precipitation pattern emerged from a drying meniscus via evaporation of a polystyrene solution in a Petri dish. It appeared a quasi-logarithmic spacing relation in the pattern as a result of stick-slip motion of the contact line towards the wall. A model based on the dynamics of the evaporating meniscus is proposed.