Tomorrow’s high-performance membranes for military and industrial use may draw on a new coatings technique that actually transfers water on a piece of fabric exclusively in one direction, rather than soaking both sides upon penetration.
Scientists in Australia and the United States have developed a technique that creates a “unidirectional water-transfer effect” on fabric. The process creates “a wettability gradient across the fabric thickness, and the treated fabrics also show considerably different breakthrough pressures on the two fabric sides,” according to the abstract for the research, recently published in the weekly Journal of Materials Chemistry.
Researchers Tong Lin and colleagues coated a porous polyester fabric on both sides with a mixture of titanium dioxide and organosilanes. This combination is similar to a common coating for superhydrophobic surfaces.
Shining UV light on one side of the fabric initiates a reaction that changes the coating; because the effect of the light diminishes as it penetrates further into the fabric, a gradient forms from one side to the other.
The side without UV light remains hydrophobic, while the other side becomes hydrophilic. When water is dropped onto the hydrophobic side of the fabric, it is quickly transported through the polyester to the hydrophilic side—and stays there.
The team believes the simple coating technique could be used to produce high-performance fabrics for military use and even industrial membranes.
A video demonstration of the coating, from both the hydrophobic and hydrophilic sides, may be viewed at http://pubs.rsc.org/en/Content/ArticleLanding/2010/JM/C0JM02364G.