Amphiphilic microparticles

Making inspiration from superhydrophobic small objects such as the scales of butterflies or moths and the legs of water striders, we have fabricated and investigated superhydrophobic microspheres with a complex surface morphology in conjunction with hydrophobic surface moieties. The combination of superhydrophobic and hydrophilic surfaces enable the stabilization between air-water interface through strong adsorption of the particles at the interface. Of particular interest is that the high mobility of the superhydrophobic microspheres gives rise to unique interfacial properties which cannot be achieved using conventional superhydrophobic materials of solid film type.

Monodisperse amphiphilic microparticles which are highly anisotropic, with a crescent-moon shape, consisting of hydrophilic convex and hydrophobic concave surfaces can be used to stabilize oil-water interface. To make such particles, monodisperse paired oil droplets of fluorocarbon and photocurable monomer are prepared in water. The monomer droplets contain silica particles which spontaneously adsorb at the aqueous interface but do not adsorb at the fluorocarbon-oil interface. After polymerization of monomer droplets and subsequent removal of fluorocarbon droplets, two different surfaces remain on each microparticle, resulting in crescent-moon shaped amphiphilic microparticles which can be used to stabilize oil drops in water. Unlike molecular surfactants which lower interfacial tension, these amphiphilic particles are densely packed at the oil-water interface, thereby preventing direct contact between neighboring drops because they are immobilized.

Encoded microparticles and sensor particles

Suspension arrays have emerged as a promising tool for biological screening and multiplex immunoassays owing to several advantages over conventional 2D planar arrays such as faster binding kinetics, large surface areas, increased statistical power and low assay cost.Suspension arrays use identification tags on the microparticles rather than the spatial information employed in planar arrays.To produce such encoded microspheres, we used simple optofluidic approach, enabling the encoding with a photocurable double emulsion system. By using core droplets with three distinct colors—red, green and blue (RGB)—we generated optically identifiable codes by controlling the numbers of the RGB core droplets encapsulated in the shell droplet. Because the RGB cores captured in the transparent shell can be identified without spectral analysis, the information can be decoded simply by counting the respective numbers of encapsulated RGB core droplets, without the need for additional decoding equipment or devices. In addition, the abundance of achievable codes can be expressed using codes comprised of a few characters. On the other hand, the surface of each shell is decorated with an array of colloidal silica beads, which enables the creation of surface functional groups for immobilizing biomolecules.