SHAPING DEW DROPLETS AT THE NANOSCALE…. INSPIRED BY NATURE
Inspired by biological systems (beetles, cacti, lizards..), “dew engineering” has emerged as a very important domain for several applications such as water harvesting, anti-fogging, open-microfluidics and fingerprint’s revealing in crime scenes.
In this context, mastering the dew droplets shaping at femtoliter scale is challenging because it requires adapted supporting surfaces and perfect control of the out-of-equilibrium conditions associated to the condensation/evaporation kinetics.
In previous reports, dew shaping could be demonstrated statically on heterogeneous hydrophilic/hydrophobic patterns by pinning the contact lines at predetermined locations.
DEW ENGINEERING on HYDROPHILIC SURFACES
Surprisingly, when exploring the wetting properties of homogenous hydrophilic nanopatterned surfaces, we revealed not only unprecedented dew droplet shaping capabilities (such as giant wetting anisotropy) but also that droplet shape could be dynamically and reversibly tuned in time.
This shaping ability was studied using state-of-the-art Environmental-Scanning Electron Microscopy (E-SEM), allowing time-resolved in situ imaging of the sub-micron droplets evolution. Indeed, the intermediate wetting property of the material is the key parameter that permits a good balance between capillary and pinning effects, both dominating the formation of the triple-phases line frontiers on nanopatterned surfaces during condensation/evaporation and in equilibrium.
Shape of single dew droplets can be dynamically and reversibly controlled by tuning the out of equilibrium conditions (such as the support temperature).
Have a look at our work here M. Faustini et al ACS Nano 2018