Biominerals exhibit morphologies, hierarchical ordering and properties that invariably surpass those of their synthetic counterparts. A key feature of these materials, which sets them apart from synthetic crystals, is their nanocomposite structure, which derives from intimate association of organic molecules with the mineral host. We here demonstrate the production of artificial biominerals where single crystals of calcite occlude a remarkable 13 wt% of 20 nm anionic diblock copolymer micelles, which act as 'pseudo-proteins'. The synthetic crystals exhibit analogous texture and defect structures to biogenic calcite crystals and are harder than pure calcite. Further, the micelles are specifically adsorbed on {104} faces and undergo a change in shape on incorporation within the crystal lattice. This system provides a unique model for understanding biomineral formation, giving insight into both the mechanism of occlusion of biomacromolecules within single crystals, and the relationship between the macroscopic mechanical properties of a crystal and its microscopic structure.

A novel, single‐step and single‐component bio‐inspired fabrication method of hierarchical superoleophobic surfaces is presented. The method consists in thermal deposition of self‐assembling ultra‐low‐surface‐energy fluorinated wax on diverse surfaces. The thermal deposition results in crystalline, oriented, three‐dimensional hierarchical structures with high surface roughness and re‐entrant curvature, which in combination with the low surface energy of the fluorinated wax results in high contact angles of low‐surface‐tension liquids and low contact‐angle hysteresis (CAH) values (Δθ). The values achieved for Δθ are below 10° even for ethanol, which exhibits a surface tension as low as 22.4 mN·m−1. In addition to their superoleophobic properties our substrates exhibit extreme superhydrophobic qualities (CAH as low as 2° and contact angle >170°) with exceptional surface stability over many months. The proposed fabrication method may be utilized for a variety of applications where non‐wetting of low‐surface‐tension liquids is required, for example non‐staining surfaces and antifouling. The ease of fabrication and the variety of substrates that can be modified will undoubtedly widen its use.

One of the most fascinating properties of materials in nature is the superhydrophobic and self‐cleaning capabilities of different plant surfaces. This is usually achieved by the hydrophobic cuticles that are made of cutin and contain wax crystals both within them and on their surfaces. Here, bioinspired n‐hexatriacontane wax films are deposited via thermal evaporation and it is shown that the surface evolves in time via self‐assembly. This leads to a dramatic change in the wetting properties with a transition from hydrophobic to superhydrophobic characteristics, which takes place within several days at room temperature. This phenomenon is investigated and strain‐induced recrystallization is proposed to be the mechanism for it. This work could become the basis for the inspiration and production of tuned, time‐dependant, temperature‐sensitive, variable‐wettability surfaces.

Our bioinspired, superhydrophobic surfaces show exceptional ability to passively inhibit the biofilm formation of Gram-positive and Gram-negative bacteria over a 7 day period.

The 3D interface between a sessile water drop that is found on a superhydrophobic microtextured surface has been directly imaged using a confocal microscope with an immersion lens. The local mean curvature of the water−air interface was derived and was shown to be constant and close to zero not only for the case of pure water, but also for cases of variable drop density and surface tension. Although the mean curvature is constant and close to zero, the standard deviation on the mean curvature increases with increasing drop density and lower surface tension. The resulting 3D image of the water−air interface at the bottom of a water drop demonstrates the possibility of investigating practical interfaces of water on given textures and confirms that no matter what the superhydrophobic surface characteristics are, the interface remains with a constant curvature of close to zero.

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SummaryThe impeding effect of plant surfaces covered with three-dimensional wax on attachment and locomotion of insects has been shown previously in numerous experimental studies. The aim of this study was to examine the effect of different parameters of crystalline wax coverage on insect attachment. We performed traction experiments with the beetle Coccinella septempunctata and pull-off force measurements with artificial adhesive systems (tacky polydimethylsiloxane semi-spheres) on bioinspired wax surfaces formed by four alkanes of varying chain lengths (C36H74, C40H82, C44H90, and C50H102). All these highly hydrophobic coatings were composed of crystals having similar morphologies but differing in size and distribution/density, and exhibited different surface roughness. The crystal size (length and thickness) decreased with an increase of the chain length of the alkanes that formed these surfaces, whereas the density of the wax coverage, as well as the surface roughness, showed an opposite relationship. Traction tests demonstrated a significant, up to 30 fold, reduction of insect attachment forces on the wax surfaces when compared with the reference glass sample. Attachment of the beetles to the wax substrates probably relied solely on the performance of adhesive pads. We found no influence of the wax coatings on the subsequent attachment ability of beetles. The obtained data are explained by the reduction of the real contact between the setal tips of the insect adhesive pads and the wax surfaces due to the micro- and nanoscopic roughness introduced by wax crystals. Experiments with polydimethylsiloxane semi-spheres showed much higher forces on wax samples when compared to insect attachment forces measured on these surfaces. We explain these results by the differences in material properties between polydimethylsiloxane probes and tenent setae of C. septempunctata beetles. Among wax surfaces, force experiments showed stronger insect attachment and higher pull-off forces of polydimethylsiloxane probes on wax surfaces having a higher density of wax coverage, created by smaller crystals.

Novel hierarchical surfaces combining paraffin wax crystals and CuO nanowires are presented. We demonstrate a bioinspired hierarchical wax on nanowire (NW) structures having high water and ethylene glycol repellence. In general, vertically grown nanowire arrays can provide a superhydrophobic surface (SHS) due to extremely high surface roughness but cannot repel ethylene glycol. In this paper, C36H74 and C50H102 waxes are thermally evaporated on the surface of CuO NWs, forming highly ordered, three-dimensional (3D) hierarchical structures via self-assembly of wax crystals. These two and three level hierarchical structures provide perfect self-cleaning characteristics, with water contact angles (CAs) exceeding 170°. Furthermore, C36H74 and C50H102 wax crystals assembled perpendicularly to the longitudinal NW axis form a re-entrant (that is, a multivalued surface topography) curvature enabling high repellence to ethylene glycol (EG) with CAs exceeding 160°. We analyze the wettability dependence on wax crystal size and structure for the optimization of nonwettable hierarchical structured surfaces.