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We report on a novel self-driven climbing of two-dimensional (2-D) ordered monolayer crystalline colloidal arrays (CCAs). This phenomenon can be used to rapidly and efficiently prepare large area, highly ordered 2-D array monolayer CCA films on various substrates. Large area 2-D polystyrene (PS) particle CCAs were fabricated on water surfaces by a needle tip flow technique. Introduction of a wet substrate through the 2-D particle monolayer array on the water surface causes the 2-D array to flow onto the wet substrate surface due to a surface spreading pressure. This method can quickly prepare ordered 2-D particle arrays on numerous wet substrates including flat/curved glass slides, inner walls of glass tubes, hydrogels, flexible polymer films, patterned surfaces, etc. By using responsive hydrogels as substrates, we can conveniently prepare 2-D photonic crystal sensors that can be used to visually determine analyte concentrations. For example, we prepared 580 nm PS 2-D arrays on poly(2-hydroxyethyl methacrylate) hydrogels to sense ethanol in water. © 2013 The Royal Society of Chemistry.

We report on a novel self-driven climbing of two-dimensional (2-D) ordered monolayer crystalline colloidal arrays (CCAs). This phenomenon can be used to rapidly and efficiently prepare large area, highly ordered 2-D array monolayer CCA films on various substrates. Large area 2-D polystyrene (PS) particle CCAs were fabricated on water surfaces by a needle tip flow technique. Introduction of a wet substrate through the 2-D particle monolayer array on the water surface causes the 2-D array to flow onto the wet substrate surface due to a surface spreading pressure. This method can quickly prepare ordered 2-D particle arrays on numerous wet substrates including flat/curved glass slides, inner walls of glass tubes, hydrogels, flexible polymer films, patterned surfaces, etc. By using responsive hydrogels as substrates, we can conveniently prepare 2-D photonic crystal sensors that can be used to visually determine analyte concentrations. For example, we prepared 580 nm PS 2-D arrays on poly(2-hydroxyethyl methacrylate) hydrogels to sense ethanol in water. © 2013 The Royal Society of Chemistry.

Nanoparticle coating: A suspension of colloidal particles in a water/propanol solution was layered onto a water surface, where the particles self-assembled into ordered two-dimensional hexagonal crystal arrays (>280 cm 2) within two minutes. These arrays were transferred from the water surface to other substrates (see picture) and embedded in a chitosan hydrogel for visual detection of the pH value. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanoparticle coating: A suspension of colloidal particles in a water/propanol solution was layered onto a water surface, where the particles self-assembled into ordered two-dimensional hexagonal crystal arrays (>280 cm 2) within two minutes. These arrays were transferred from the water surface to other substrates (see picture) and embedded in a chitosan hydrogel for visual detection of the pH value. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The first quantitative study of how the mechanical properties of a swollen hydrogel depend upon the diameter of nonbonded embedded nanoparticles was studied. Monodisperse, highly charged polystyrene colloidal particles with diameters between 114 and 186 nm were used in the preparation of the PCCA studied. The PCCA studied were synthesized by UV initiated free radical polymerization of a hydrogel around the CCA. The CCA solutions used for the PCCA preparations were composed of identical weight percent particle dispersions in water to ensure constant overall polymer content within the corresponding pre-polymerization solutions. This linear dependence derives primarily from the contribution of slip within the system, which varies based on the surface area of the embedded particles. We also found that the increase in storage modulus upon exclusion of oxygen during polymerization is more pronounced for hydrogels without nanoparticle inclusions and that the modulus is dominated by particle inclusions as opposed to the cross-linker.

The first quantitative study of how the mechanical properties of a swollen hydrogel depend upon the diameter of nonbonded embedded nanoparticles was studied. Monodisperse, highly charged polystyrene colloidal particles with diameters between 114 and 186 nm were used in the preparation of the PCCA studied. The PCCA studied were synthesized by UV initiated free radical polymerization of a hydrogel around the CCA. The CCA solutions used for the PCCA preparations were composed of identical weight percent particle dispersions in water to ensure constant overall polymer content within the corresponding pre-polymerization solutions. This linear dependence derives primarily from the contribution of slip within the system, which varies based on the surface area of the embedded particles. We also found that the increase in storage modulus upon exclusion of oxygen during polymerization is more pronounced for hydrogels without nanoparticle inclusions and that the modulus is dominated by particle inclusions as opposed to the cross-linker.