If deposited on a hydrophobic rough substrate, a small drop of water can look like a pearl, with a contact angle close to 180°. We examine the conditions for observing such a phenomenon and show practical achievements where the contact angle can be predicted and thus quantitatively tuned by the design of the surface microstructure.

This paper demonstrates a new method for the synthesis of mixed self-assembled monolayers (mixed SAMs) by reaction of a reactive intermediatean interchain carboxylic anhydridewith alkylamines. The interchain anhydride was prepared in high yield from a SAM of 16-mercaptohexadecanoic acid (HS(CH2)15COOH) on gold by treatment with trifluoroacetic anhydride. Alkylamines reacted cleanly with the interchain anhydride to generate a mixed SAM, which comprised a mixture of acids and amides in approximately 1:1 ratio on the surface. The SAMs of the interchain anhydride and the mixed SAM were characterized using polarized infrared external reflectance spectroscopy, X-ray photoelectron spectroscopy, contact angle, and ellipsometry. Control of the wettability of the SAMs was demonstrated by allowing the interchain anhydride to react with alkylamines having different alkyl groups; this model system gave wetting data consistent with earlier studies of mixed monolayers and verified the ability of this method to manipulate interfacial physical properties. In certain circumstances, this method is experimentally simpler as a method to produce mixed SAMs than are conventional methods involving coadsorption of two thiols from a mixture in solution. It also assures two other characteristics of the mixed SAM:  that the composition of the SAM is roughly 1:1 in carboxylic acid and amide groups, and that these two groups are well mixed on the surface.

This paper describes the fabrication of free-standing high-carbon microstructures by softlithographic techniques; these structures ranged in complexity from simple beams to complex, suspended deflectors. Microstructures of polymeric precursors (copolymers of furfuryl alcohol-phenol) to high-carbon solids were fabricated using poly(dimethylsiloxane) (PDMS) molds. Carbonization of these microstructures under argon resulted in mass loss (up to 45%) and shrinkage (up to 20% linearly); the density increased to reach a plateau value of ∼1.5 g/cm 3 at ∼900 °C. Microstructures pyrolyzed at 900 °C were electrically conductive, with a conductivity of ∼10 -2 Ω cm. Elementary microelectromechanical functions were demonstrated in these microstructures: electrostatic actuation induced deflection or vibrations of suspended structures. The measurement of the frequency of resonance of highcarbon cantilevered beams allowed the determination of Young's modulus for the solid: typical values were ∼15-20 GPa. The microelectromechanical properties of more complex structures (microresonators, light deflectors) were also determined. This paper demonstrates that high-carbon microstructures can be easily fabricated that have potential use as the active components of MEMS.

This paper demonstrates that the molding of a sol-gel precursor against an elastomeric replica of the desired features (a form of soft lithography) [1] is a convenient method to generate submicrometer patterns of glasses on a substrate. We were able to fabricate glass (silicon dioxide doped with boron oxide, titanium oxide, or aluminum oxide) structures with micrometer-scale features supported on a flat Si/SiO 2 substrate, as well as free-standing membranes.In molding, an initially fluid material is allowed to acquire its final geometry by solidifying in a mold. This technique allows the reproduction of the fine details of the mold: replica molding of structures in polymers has generated structures with 10 nm sized features.[2] The molding of sol-gel precursor solutions has produced monolithic silica pieces [3] as well as Fresnel lenses or gratings with sub-micrometer periods.[4] Replica molding is a method that has several potentially useful features. It does not require photolithography and can be used without access to a clean room. Once the mold is fabricated, many replicas can be produced.[2] It has a theoretical limit to resolution that is much below that that can be achieved by photolithography. It can be used to make patterns on curved substrates. The throughput of a process based on molding can be high and its cost low. Unlike electron-beam or scanning tunneling microscopy (STM) writing, molding allows parallel fabrication. We believe that micro-molding is a type of process that will be widely useful in microfabrication. The sol-gel process is a versatile method for synthesizing many inorganic oxides.[5] This method generates materials with controlled chemical composition and low levels of impurities. Most common glasses, with the exception of some halide glasses, have been successfully synthesized; these compositions range from high purity silica to an eight-component glass ceramic. [6] Other materials that have been prepared by sol-gel process include PZT ceramics (i.e., Pb(Zr,Ti)O 3 ), [7,8] electro-optic films, [9] high efficiency phosphors, [10] and electrochromic glasses.[11]The use of sol-gel chemistry to prepare materials has one unattractive characteristic: the shrinkage induced in the drying stage gives rise to high stresses in the structures. These stresses can cause the deformation and breaking of the structures. In order to reduce these stresses, drying additives can be used.[12] The incorporation of non-hydrolyzing organic groups in the material (methyl or phenyl) gives structures with higher compliance and allows structural relaxation during the drying stage.[13] Controlled slow drying can also decrease the risk of cracking of the glass; it will, however, result in long process times. Good adhesion of the glass to the substrate is necessary to prevent the delamination of the structure. We wished to fabricate glass structures with dimensions in the range of 0.1 mm to several micrometers by non-lithographic methods, and have examined the molding of solgels in an elastomeric mold. This pape...

The segment density profile of anchored layers of poly(dimethylsiloxane) in good solvents has been measured using neutron reflectometry. Two types of layers have been studied: end-grafted layers (brushes) and irreversibly adsorbed layers, on silicon/silicon dioxide. The latter can be viewed as a polydisperse brush of loops and was obtained by adsorbing the polymer from the melt or from a concentrated solution. A model-free constrained fitting procedure was developed, which gave the concentration profile with a good precision. We present this numerical method and the concentration profiles obtained for the different layers. The profiles of the two types of layers are significantly different. They are in agreement with self-consistent mean field theory for the brushes and with scaling laws descriptions for the irreversibly adsorbed layers. The reflectivity measurement enabled us to verify precisely that the concentration profile in the brush cannot be described by a step function with a Gaussian roughness but has a parabolic shape.