Meso-scale imaging of patterned surfaces by decoration with liquid crystals

We report techniques for the imaging of patterned surfaces that are based o n the use of random arrays of microdroplets of the nematic liquid crystal 4 -cyano-4'-pentylbiphenyl (5CB). Microdroplets of 5CB were delivered to surf aces by spray atomization of a nematic phase or by condensation of a vapor of mesogens. By comparing the optical textures of microdroplets of 5CB in t heir isotropic and nematic states, we conclude that microdroplets of liquid crystals (LCs) can be used to image patterned surfaces that cannot be imag ed by using microdroplets of isotropic liquids (conventional 'breath figure s'). We demonstrate, for example, the use of random arrays of microdroplets of nematic 5CB to image (i) patterned, low-energy SAMs formed from H3C(CH2 )(14)SH and H3C(CH2)(15)SH on films of Sold and (ii) Sold films that are pa tterned with regions that differ in their roughness ton the 1-10 nm scale) and which support SAMs formed from H3C(CH2)(14)SH. On the low energy surfac es, we observed the optical appearances of the microdroplets of LCs to be i ndifferent to their manner of deposition (spray or condensation) but depend ent on their size. In particular, when using microdroplets with diameters < similar to 45 mu m, the optical appearances of the microdroplets were inse nsitive to the structures of the surfaces on which they were deposited. How ever, by using larger microdroplets and by observing the optical structure within a given microdroplet of LC, it was possible to image patterns with l ateral dimensions substantially smaller than 45 mu m. We also report the us e of nematic 5CB to image patterned, high energy SAMs formed from HOOC(CH2) (10)SH and NaOOC(CH2)(10)SH that are uniformly wet by both isotropic and ne matic liquids. (C) 2000 Elsevier Science B.V. All rights reserved.