Superhydrophobic and Superhydrophilic Surfaces

M.B. Herzog, J.H. Johnston, M. Franzreb
Victoria University of Wellington, NZ

Keywords: superhydrophobic, superhydrophilic, hierarchical structure, contact angle hysteresis, roll-off angle, 3D printing, wool, polymers

Summary:

A new generation of materials possessing a wide range of possible consumer applications such as water harvesting, stain resistant self-cleaning and water-repellent breathable surfaces are being fabricated. Based on nature’s example of the stenocara beetle, superhydrophobic and superhydrophilic surfaces have been developed, using either a hierarchical surface structure in the micro and nano range, created via layer-by-layer assembly of functionalised silica nanospheres of different diameters, or a single level surface structure. Both, woven and non-woven woollen textile substrates were modified. Static contact angles of 160°, with corresponding contact angle hysteresis and roll-off angles below 20° for a 10 µL droplet have been measured. The obtained knowledge of the structural design and chemical surface alterations through Dynasylan® or perfluorooctylamine was then combined with theoretical calculations. By utilizing 3D printing an array of new surface patterns was developed which show promising results. Single level surface structures open up a simple and inexpensive way to fabricate both superhydrophobic and superhydrophilic patterned surfaces and the combination of both types of surfaces allows the creation of a patterning similar to that of the beetle.