Multi-functional Surfaces with Controllable Wettability and Water Adhesion

The design of multifunctional surfaces based on biomimetic structures has gained the interest of the scientific community. Such biomimetic structures can be achieved by using “smart” coatings, which can respond to external stimuli, such as light, temperature, electric field, pH or solvent selectivity, onto appropriately structured substrates. Novel multifunctional surfaces have been developed, able to alter their wetting properties in response to temperature and/or pH as well as light illumination, by combining proper chemistry and surface micro/nano-structuring. For this purpose, dual scale micro/nano-roughened surfaces are prepared by either irradiating Si wafers using ultrafast (femtosecond) laser under a reactive atmosphere or by utilizing inorganic additives within a polymer nanocomposite; appropriate chemistry of the polymeric coatings can, the, provide the desired functionality. Utilization of end-functionalized polymer chains anchored onto the hierarchical surfaces can lead to surfaces that exhibit reversible and controllable wettability to temperature and/or pH from the “parahydrophobic” behavior of natural plant leaves all the way to superhydrophilic properties in response to external stimuli. Moreover, altering the irradiation conditions results in surfaces with directional motion of the water droplets. Finally, when polymeric substrates are of interest, one can utilize composite coatings where the colloidal particles create the appropriate roughness and the polymer matrix provides the proper functionality.

Acknowledgements: This research has been co-financed by EU and Greek national funds (Action RESEARCH – CREATE - INNOVATE, project INGRECO, MIS: 5030174).