ESR 07: Deposition of nanoparticles during spreading and evaporation of nanofluid drops in the presence of superspreading and non-superspreading trisiloxane surfactants on hydrophobic substrates

To understand the superspreading mechanism by studying drop spreading, evaporation and deposition of nanoparticles. To control the nanoparticles deposition and pattern formation using superspreaders and other surfactants and examining the effect of environmental conditions (temperature and humidity)
Expected Results:
– Experimental data on drop spreading dynamics under action of superspreaders and other surfactants as a comparison (at the premises of EVO, Essen);
– Parameter studies of assembling of nanoparticles and pattern formation in the presence of superspreaders and other surfactants and under controlled environmental conditions (at TUDA);
– Interpretation of experimental results on the basis of model developed by ESR4.

  • Surface tension behavior of superspreading and non-superspreading trisiloxane surfactants

    One parameter frequently considered to be relevant for superspreading of trisiloxane surfactants is surface tension kinetics. In the scientific literature, some experimental results reported for trisiloxane surfactants are in contradiction with fundamental concepts of surfactant monomer diffusion. Therefore, maximum bubble pressure tensiometry has been used to determine dynamic surface tension (DST) of two types of trisiloxane surfactants: superspreader and non-superspreader. Results show that both surfactants behave similarly at concentrations below critical micelle concentration (CMC), as expected. The CMC curves, as determined by drop shape analysis, confirmed that the more hydrophilic non-superspreader has a higher CMC as compared to the more hydrophobic superspreader. Accordingly, the lower surfactant monomer concentration of the superspreader results in a higher DST than the non-superspreader at the same surface age. So, in contrary to claims in the literature, there is nothing mysterious or unexpected concerning the surface tension behavior of trisiloxane surfactants.

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