Durable Superhydrophobic Surfaces via Spontaneous Wrinkling of Teflon AF

Abstract

We report the fabrication of both single-scale and hierarchical superhydrophobic surfaces, created by exploiting the spontaneous wrinkling of a rigid Teflon AF film on two types of shrinkable plastic substrates. Sub-100 nm to micrometric wrinkles were reproducibly generated by this simple process, with remarkable control over the size and hierarchy. Hierarchical Teflon AF wrinkled surfaces showed extremely high water repellence (contact angle 172°) and very low contact angle hysteresis (2°), resulting in droplets rolling off the surface at tilt angles lower than 5°. The wrinkling process intimately binds the Teflon AF layer with its substrate, making these surfaces mechanically robust, as revealed by macroscale and nanoscale wear tests: hardness values were close to that of commercial optical lenses and aluminum films, resistance to scratch was comparable to commercial hydrophobic coatings, and damage by extensive sonication did not significantly affect water repellence. By this fabrication method the size of the wrinkles can be reproducibly tuned from the nanoscale to the microscale, across the whole surface in one step; the fabrication procedure is extremely rapid, requiring only 2 min of thermal annealing to produce the desired topography, and uses inexpensive materials. The very low roll-off angles achieved in the hierarchical surfaces offer a potentially up-scalable alternative as self-cleaning and drag-reducing coatings.

Superhydrophobic Coatings with Periodic Ring Structured Patterns for Self‐Cleaning and Oil–Water Separation

“…In order to achieve superhydrophobicity, a surface with low energy molecules and rough morphology is usually required . However, the hydrophobic materials and surface modification made from organic molecules containing fluorine are usually not cost‐effective and not environmentally friendly . Therefore, it is a great challenge to develop a superhydrophobic surface with a facile and cost‐effective fabrication method …”

Self‐Healing Functional Surfaces

“…Of course, we all know the prototype of an ideal low surface energy polymer to design low adherence surfaces, i.e., polytetrafluoroethylene (PTFE, Teflon ), but the properties of this polymer do not allow wide applications; obviously, there is little interest or benefit in fully covering a boat or oil‐refinery pipelines with Teflon . For some applications, however, this might still be an interesting material, e.g., in combination with the SLIPS approach for use in medical devices, using induced surface wrinkling to shape its surface behavior or finding clever ways of designing the polymer architectures and their surface dynamics to gain Teflon‐ like behavior on specific environmental conditions, such as using block ‐copolymer architectures, hybrids, stimuli‐responsive materials, and/or self‐assembled hierarchical structures.…”

Performance properties and applications of polytetrafluoroethylene (PTFE)—a review

“…Wrinkled superhydrophobic surfaces, fabricated from two forms of PTFE exhibit the durable and excellent barrier properties as the roll-off angle of the surfaces tend to be very low. The contact angle for single-scale wrinkled PTFE and hierarchical wrinkled PTFE surface was measured at 163°and 172°that has been possessing higher magnitude [11]. Surface modification of PTFE from hydrophobic to hydrophilic property was optimized by the addition of chemical agents amino (-NH 2 ), carboxyl (-COOH) and sulfonic acid (-SO 3 H).…”