Combining biomimetic principles from the lotus leaf and mussel adhesive: polystyrene films with superhydrophobic and adhesive layers

Abstract

Lotus leaves are well known for their extremely water repellent surfaces. Marine mussels are also a popular research topic when considering biological adhesives. Both organisms have inspired the development of several biomimetic materials. Herein we describe a two-sided film made almost entirely from polystyrene onto which the properties of both lotus leaves and mussel adhesive are incorporated. On one side of the film, imparting micrometer and nanometer scale hierarchical roughness yields superhydrophobicity and water repellency, which facilitates rapid fluid flow. The other side of the film is modified with a copolymer mimic of 3,4-dihydroxyphenylalanine (DOPA)-containing mussel adhesive proteins. This copolymer incorporates 3,4-dihydroxystyrene, to represent DOPA, randomly into a polystyrene host polymer. The flexibility of the polystyrene backing film enabled rolling of the assembly into a tubular shape. Inside the polystyrene tube was the superhydrophobic lotus mimic. The mussel adhesive mimic, on the outer layer, was used to glue the tube to itself, thus maintaining the tubular shape. The film was also successfully glued to a variety of flat substrates. These two-dimensional and three-dimensional assemblies can be used to direct and localize the flow of fluids, with partitioning between superhydrophobic and relatively hydrophilic regions. Such assemblies may facilitate the design of liquid transport for industrial and biomedical devices.

Wettability of natural superhydrophobic surfaces

“…The most famous of these, and perhaps the archetype for natural superhydrophobic surfaces, is the lotus leaf [16]. Natural surfaces such as this have inspired the fabrication of countless synthetic analogues in an attempt to reproduce the extremely low wettability and other associated desirable properties of these substrata [17][18][19][20][21]. Given their significance as the templates on which new superhydrophobic materials are based, it is the intention of this review to discuss the mechanisms of superhydrophobicity with respect to natural surfaces, and identify the factors that make them extremely effective at repelling water.…”

Biomimetic Miniaturized Platform Able to Sustain Arrays of Liquid Droplets for High‐Throughput Combinatorial Tests

“…This feature was achieved by the introduction of micro‐ and nanoroughness ( Figure a), without further chemical modification of the polymeric structure. Such substrates present a similar topography previously observed in polystyrene SH substrates . The developed surfaces patterned with adhesive micro‐indentations (Figure b) were used as support for arrays of aqueous solution‐based droplets.…”

“…The size and composition can be easily controlled in an individual form, and the processes in the liquid state occur with minimum contact with the solid substrate. Furthermore, the SH platform is solely physically modified polystyrene (PS), which guarantees the lack of cytotoxicity and the chemical stability of the platform.…”

Recent advances on open fluidic systems for biomedical applications: A review

“…The fabrication of surfaces with (super)hydrophobic/(super)hydrophilic patterning may rely on different principles [45,72,73]. Some examples of strategies used to achieve these patterns include (i) the protection of the wettable areas, which should remain untreated to showcase wettable properties, using an adhesive mask or an inkjetprinted sacrificial layer prior to the hydrophobization process [71,[74][75][76][77][78]; (ii) the use of photomasks, stencil masks or sacrificial protective coatings to promote the selective exposure of the (super) hydrophobic surface to treatment targeted at the wettability increase, such as UV [79,80] or UV/ozone irradiation [81,82], or plasma treatment [67,83]; (iii) direct writing of the desired pattern by laser on the (super)hydrophobic surface [84,85]; using printing techniques, through the deposition of molecules that go through oxidative self-polymerization or lipid solutions onto (super)hydrophobic surfaces originating the desired (super)hydrophilic patterns [56,69].…”