Catalytic, Self-Cleaning Surface with Stable Superhydrophobic Properties: Printed Polydimethylsiloxane (PDMS) Arrays Embedded with TiO₂ Nanoparticles

Abstract

Maintaining the long-term stability of superhydrophobic surfaces is challenging because of contamination from organic molecules and proteins that render the surface hydrophilic. Reactive oxygen species generated on a photocatalyst, such as TiO2, could mitigate this effect by oxidizing these contaminants. However, incorporation of such catalyst particles into a superhydrophobic surface is challenging because the particles become hydrophilic under UV exposure, causing the surface to transition to the Wenzel state. Here we show that a high concentration of hydrophilic TiO2 catalytic nanoparticles can be incorporated into a superhydrophobic surface by partially embedding the particles into a printed array of high aspect ratio polydimethylsiloxane posts. A stable Cassie state was maintained on these surfaces, even under UV irradiation, because of the significant degree of hierarchical roughness. By printing the surface on a porous support, oxygen could be flowed through the plastron, resulting in higher photooxidation rates relative to a static ambient. Rhodamine B and bovine serum albumin were photooxidized both in solution and after drying onto these TiO2-containing surfaces, and the effects of particle location and plastron gas composition were studied in static and flowing gas environments. This approach may prove useful for water purification, medical devices, and other applications where Cassie stability is required in the presence of organic compounds.

Fluorinated Photodynamic Therapy Device Tips and their Resistance to Fouling for In Vivo Sensitizer Release

“…Lastly, we now know there is a complimentary effect where the fluorinated tip 1 not only repels biofoulants better, it also suppresses surface 1 O 2 physical quenching for a more efficient sensitizer photorelease. It could be argued that added biofouling protection results from the production of 1 O 2 at the surface of tips 1 and 5 as has been observed for other surfaces which produce 1 O 2 or ROS . We believe that generation of 1 O 2 on (or near) the tip will retard and/or prevent fouling on/near that surface.…”

Recent Progress in Fabrication and Applications of Superhydrophobic Coating on Cellulose-Based Substrates

“…Self-cleaning materials are attracting more and more attention for its convenience and environment friendliness [145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167]. …”

“…Lyons et al described a self-cleaning superhydrophobic PDMS post arrays partially embedded with TiO 2 nanoparticles. The composited surface maintained superhydrophobicity with a typical Cassie wetting state even when the hydrophilic TiO 2 nanoparticles were embedded, and exhibited good super-antiwetting property after a long-term UV light irradiation (Figure 16) [166]. However, the conjugated dye, rhodamine B, and a bovine serum albumin protein were efficiently color removed or photo-oxidized by the inherent UV photocatalytic degradation ability of anatase TiO 2 nanostructure materials [167].…”

“…Inset pictures are the rhodamine B solution before (left) and after (right) UV photodegradation. (Reprinted from Reference [166] with permission).…”

Robust transparent superamphiphobic coatings on non-fabric flat substrates with inorganic adhesive titania bonded silica

“…Since the superamphiphobic surfaces are theoretically repellent only to bulk liquids, tiny organic pollutants contained in the floating fog and smoke could attach to the superamphiphobic surfaces, therefore altering the surface energy and gradually worsening superrepelling performance. Applying photoactive agent, [45][46][47][48] such as TiO2, to the surfaces could improve the stability against pollutants through photo decomposition of organic contaminants, which provides self-healing ability to superamphiphobic surfaces.…”