Nanoscopic channel lattices with controlled anisotropic wetting

Abstract

Engineered microscopic surface structures allow local control of physical surface properties such as adhesion, friction and wettability. These properties are related both to molecular interactions and the surface topology^1,2—for example, selective adsorption and molecular recognition capabilities³ require controlled anisotropy in the surface properties. Chemistry with extremely small amounts of material has become possible using liquid-guiding channels of sub-micrometre dimensions^4,5,6. Laterally structured surfaces with differing wettabilities may be produced using various techniques, such as microcontact printing^7,8,9, micromachining¹⁰, photolithography^11,12 and vapour deposition¹³. Another strategy¹⁴ for introducing anisotropic texture is based on the use of the intrinsic material properties of stretched ultrathin polymer coatings. Here we present a fast and simple method to generate extended patterned surfaces with controlled wetting properties on the nanometre scale, without any lithographic processes. The technique utilizes wetting instabilities that occur when monomolecular layers are transferred onto a solid substrate. The modified surfaces can be used as templates for patterning a wide variety of molecules and nanoclusters into approximately parallel channels, with a spatial density of up to 20,000 cm^-1.We demonstrate the transport properties of these channels for attolitre quantities of liquid.