(322c) Mechanically Robust Nanoparticle Stabilized Transparent Liquid Marbles

Liquid marbles are non-wetting liquid drops coated with hydrophobic powder. The presence of the particles on the free surface causes the effective liquid-solid interfacial tension to decrease substantially resulting in near non-wetting conditions. A common necessity of micro-fluidic devices is to be able to easily and controllably manipulate minute quantities of liquids and to be able to cause chemical reactions between such quantities of liquids. Liquid marbles have been shown to possess the potential to deliver upon these promises. However it is known that the ability to use liquid marbles in microfluidic devices is currently limited by their mechanical robustness. Here we present, remarkably robust transparent liquid marbles of glycerol and water under both compressive and tensile loading conditions formed using commercially available nanoparticulate fumed silica treated with hydrophobic agent, Hexamethyldisalazane (nHFS) and micron size polytetrafluoroethylene powder (mPTFE). ESEM and mass transfer data are used to investigate the cause of this robustness. Liquid marble evaporation data indicates that the nanoparticulate fumed silica marbles are more robust due to increased particle-particle interaction. During the evaporation process convective flows within the evaporating drop causes hydrophobic particles to self-organize and form a robust 2-dimensional array on the liquid-vapor interface. We also report translucent liquid marbles if not entirely transparent formed using nHFS particles. Transparent liquid marbles allow the contents of the liquid marbles to be probed optically during transport.