Pressure/electric-field-assisted micro/nanocasting method for replicating a lotus leaf

Influence of Nanotechnology and the Role of Nanostructures in Biomimetic Studies and Their Potential Applications

With the advent of nanotechnology, by looking further deep down into the molecular level, today, we are able to understand basic and applied sciences even better than ever before. Not only has nanoscience and nanotechnology allowed us to study the composing structures of materials in detail, it has also allowed us to fabricate and synthesize such nanostructures using top-down and bottom-up approaches. One such field, which has been significantly influenced by the dawn of nanotechnology is biomimetics. With powerful spectroscopic and microscopic tools presenting us with images like double nanostructured pillars on the lotus surface for superhydrophobicity, the conical protuberances of moth eye demonstrating anti-reflection properties and nanostructured spatulae of gecko feet for high adhesivity, we are now able to fabricate these structures in the lab with properties showing close resemblance to their natural counterparts. Here, we present a review of various nanostructures that exist in nature, their fabrication techniques and some of their promising future applications. We hope this review will provide the reader with a basic understanding of what biomimetics is and how nanotechnology has significantly influenced this field.

Biomimetic polymeric superhydrophobic surfaces and nanostructures: from fabrication to applications

Numerous research studies have contributed to the development of mature superhydrophobic systems. The fabrication and applications of polymeric superhydrophobic surfaces have been discussed and these have attracted tremendous attention over the past few years due to their excellent properties. In general, roughness and chemical composition, the two most crucial factors with respect to surface wetting, provide the basic criteria for yielding polymeric superhydrophobic materials. Furthermore, with their unique properties and flexible configurations, polymers have been one of the most efficient materials for fabricating superhydrophobic materials. This review aims to summarize the most recent progress in polymeric superhydrophobic surfaces. Significantly, the fundamental theories for designing these materials will be presented, and the original methods will be introduced, followed by a summary of multifunctional superhydrophobic polymers and their applications. The principles of these methods can be divided into two categories: the first involves adding nanoparticles to a low surface energy polymer, and the other involves combining a low surface energy material with a textured surface, followed by chemical modification. Notably, surface-initiated radical polymerization is a versatile method for a variety of vinyl monomers, resulting in controlled molecular weights and low polydispersities. The surfaces produced by these methods not only possess superhydrophobicity but also have many applications, such as self-cleaning, self-healing, anti-icing, anti-bioadhesion, oil-water separation, and even superamphiphobic surfaces. Interestingly, the combination of responsive materials and roughness enhances the responsiveness, which allows the achievement of intelligent transformation between superhydrophobicity and superhydrophilicity. Nevertheless, surfaces with poor physical and chemical properties are generally unable to withstand the severe conditions of the outside world; thus, it is necessary to optimize the performances of such materials to yield durable superhydrophobic surfaces. To sum up, some challenges and perspectives regarding the future research and development of polymeric superhydrophobic surfaces are presented.

Superhydrophobic surfaces developed by mimicking hierarchical surface morphology of lotus leaf

The lotus plant is recognized as a ‘King plant’ among all the natural water repellent plants due to its excellent non-wettability. The superhydrophobic surfaces exhibiting the famous ‘Lotus Effect’, along with extremely high water contact angle (>150°) and low sliding angle (<10°), have been broadly investigated and extensively applied on variety of substrates for potential self-cleaning and anti-corrosive applications. Since 1997, especially after the exploration of the surface micro/nanostructure and chemical composition of the lotus leaves by the two German botanists Barthlott and Neinhuis, many kinds of superhydrophobic surfaces mimicking the lotus leaf-like structure have been widely reported in the literature. This review article briefly describes the different wetting properties of the natural superhydrophobic lotus leaves and also provides a comprehensive state-of-the-art discussion on the extensive research carried out in the field of artificial superhydrophobic surfaces which are developed by mimicking the lotus leaf-like dual scale micro/nanostructure. This review article could be beneficial for both novice researchers in this area as well as the scientists who are currently working on non-wettable, superhydrophobic surfaces.

Effects of a cell-imprinted poly(dimethylsiloxane) surface on the cellular activities of MG63 osteoblast-like cells: preparation of a patterned surface, surface characterization, and bone mineralization

To understand the relationship between surface patterns and cellular activities, various types of pattern models have been investigated. In this study, we suggest a new surface pattern model, which replicates proliferated cells. We used osteoblast-like cells (MG63) as a target cell pattern and constructed various cell-imprinted surfaces using an electric field assisted casting method for different culturing times (4 h and 7 and 14 days). On the basis of scanning electron microscopy images and three-dimensional topographical optical images, we acquired the cells' unique patterns and used them for replicating patterned substrates. We then cultured MG63 cells in the patterned surfaces for 7 and 14 days to observe various cellular activities, cell viability, alkaline phosphatase (ALP) activity, and mineralization. Higher cellular activities were observed on the roughened surface as compared with the smooth surface. In particular, we obtained the most appropriate roughness value (R(a) = 702 ± 87 nm) from proliferated cells cultured over 14 days. On the basis of these findings, we demonstrate a new biomimical surface model that enhances cellular activities at the cell-substrate interface.

Diffraction grating with suppressed zero order fabricated using dielectric forces

An electric-field-assisted method to produce diffractive optical devices is demonstrated. A uniform film of liquid UV curable resin was produced as a drying ring from an organic solvent. Dielectrophoresis forces maintained the stability of the thin film and also imprinted a periodic corrugation deformation of pitch 20 μm on the film surface. Continuous in situ voltage-controlled adjustment of the optical diffraction pattern was carried out simultaneously with UV curing. A fully cured solid phase grating was produced with the particular voltage-selected tailored optical property that the zero transmitted order was suppressed for laser light at 633 nm.