42 research outputs found
Building micro-soccer-balls with evaporating colloidal fakir drops
Evaporation-driven particle self-assembly can be used to generate
three-dimensional microstructures. We present a new method to create these
colloidal microstructures, in which we can control the amount of particles and
their packing fraction. To this end, we evaporate colloidal dispersion droplets
on a special type of superhydrophobic micro-structured surface, on which the
droplet re- mains in Cassie-Baxter state during the entire evaporative process.
The remainders of the droplet consist of a massive spherical cluster of the
microspheres, with diameters ranging from a few tens up to several hundreds of
microns. We present scaling arguments to show how the final particle packing
fraction of these balls depends on the dynamics of the droplet evaporation.Comment: Manuscript Submitted to Physical Review Letters, 29th February 201
Color Tuning of Electrochromic TiO<sub>2</sub> Nanofibrous Layers Loaded with Metal and Metal Oxide Nanoparticles for Smart Colored Windows
Co-axial electrospinning was applied for the structuring of non-woven webs of TiO2 nanofibers loaded with Ag, Au, and CuO nanoparticles. The composite layers were tested in an electrochromic half-cell assembly. A clear correlation between the nanoparticle composition and electrochromic effect in the nanofibrous composite is observed: TiO2 loaded with Ag reveals a black-brown color, Au shows a dark-blue color, and CuO shows a dark-green color. For electrochromic applications, the Au/TiO2 layer is the most promising choice, with a color modulation time of 6 s, transmittance modulation of 40%, coloration efficiency of 20 cm2/C, areal capacitance of 300 F/cm2, and cyclic stability of over 1000 cycles in an 18 h period. In this study, an unexplored path for the rational design of TiO2-based electrochromic device is offered with unique color-switching and optical efficiency gained by the fibrous layer. It is also foreseen that co-axial electrospinning can be an alternative nanofabrication technique for smart colored windows. </p