Omniphobic coatings are designed to repel a wide range of liquids without leaving stains on the surface. A practical coating should exhibit stable repellency, show no interference with color or transparency of the underlying substrate and, ideally, be deposited in a simple process on arbitrarily shaped surfaces. We use layer-by-layer (LbL) deposition of negatively charged silica nanoparticles and positively charged polyelectrolytes to create nanoscale surface structures that are further surface-functionalized with fluorinated silanes and infiltrated with fluorinated oil, forming a smooth, highly repellent coating on surfaces of different materials and shapes. We show that four or more LbL cycles introduce sufficient surface roughness to effectively immobilize the lubricant into the nanoporous coating and provide a stable liquid interface that repels water, low-surface-tension liquids and complex fluids. The absence of hierarchical structures and the small size of the silica nanoparticles enables complete transparency of the coating, with light transmittance exceeding that of normal glass. The coating is mechanically robust, maintains its repellency after exposure to continuous flow for several days and prevents adsorption of streptavidin as a model protein. The LbL process is conceptually simple, of low cost, environmentally benign, scalable, automatable and therefore may present an efficient synthetic route to non-fouling materials.

Omniphobic fluorogel elastomers were prepared by photocuring perfluorinated acrylates and a perfluoropolyether crosslinker. By tuning either the chemical composition or the temperature that control the crystallinity of the resulting polymer chains, a broad range of optical and mechanical properties of the fluorogel can be achieved. After infusing with fluorinated lubricants, the fluorogels showed excellent resistance to wetting by various liquids and anti-biofouling behavior, while maintaining cytocompatiblity.

Rational design strategies for mechano-responsive optical material systems are created by introducing a simple experimental system that can continuously vary the state of bi-axial stress to induce various wrinkling patterns, including stripes, labyrinths, herringbones, and rarely observed checkerboards, that can dynamically tune the optical properties. In particular, a switching of two orthogonally oriented stripe wrinkle patterns from oxidized polydimethylsiloxane around the critical strain value is reported, as well as the coexistence of these wrinkles forming elusive checkerboard patterns, which are predicted only in previous simulations. These strain-induced wrinkle patterns give rise to dynamic changes in optical transmittance and diffraction patterns. A theoretical description of the observed pattern formation is presented which accounts for the residual stress in the membrane and allows for the fine-tuning of the window of switching of the orthogonal wrinkles. Applications of wrinkle-induced changes in optical properties are demonstrated, including a mechanically responsive instantaneous privacy screen and a transparent sheet that reversibly reveals a message or graphic and dynamically switches the transmittance when stretched and released.