Fog Collection Based on Secondary Electrohydrodynamic-Induced Hybrid Structures with Anisotropic Hydrophilicity

Strategies in surface engineering for the regulation of microclimates in skin-medical product interactions

There is a growing number of personal healthcare devices that are in prolonged contact with the skin. The functionality of these products is linked to the interface formed by the contact between the medical apparatus and the skin. The interface can be characterised by its topology, compliance, and moisture and thermal regulating capabilities. Many devices are, however, described to have suboptimal and occlusive contacts, resulting in physiological unfavourable microclimates at the interface. The resulting poor management of moisture and temperature can impact the functionality and utility of the device and, in severe cases, lead to physical harm to the user. Being able to control the microclimate is therefore expected to limit medical-device related injuries and prevent associated skin complications. Surface engineering can modify and potentially enhance the regulation of the microclimate factors surrounding the interface between a product's surface and the skin. This review provides an overview of potential engineering solutions considering the needs for, and influences on, regulation of temperature and moisture by considering the skin-medical device interface as a system. These findings serve as a platform for the anticipated progress in the role of surface engineering for skin-device microclimate regulation.

Electrohydrodynamic Nanopatterning: A Novel Solvent-Assisted Technique for Unconventional Substrates

Electrohydrodynamic (EHD)-driven patterning is a pioneering lithographic technique capable of replicating and modifying micro/nanostructures efficiently. However, this process is currently restricted to conventional substrates, as it necessitates a uniform and robust electric field over a large area. Consequently, the use of nontraditional substrates, such as those that are flexible, nonflat, or have high insulation, has been notably limited. In our study, we extend the applicability of EHD-driven patterning by introducing a solvent-assisted capillary peel-and-transfer method that allows the successful removal of diverse EHD-induced structures from their original substrates. Compared with the traditional route, our process boasts a success rate close to 100%. The detached structures can then be efficiently transferred to nonconventional substrates, overcoming the limitations of the traditional EHD process. Our method exhibits significant versatility, as evidenced by successful transfer of structures with engineered wettability and patterned structures composed of metals and metal oxides onto nonconventional substrates.

Rapid Electrohydrodynamic-Driven Pattern Replication over a Large Area via Ultrahigh Voltage Pulses

Despite the prospects of electrohydrodynamic instability patterning (EHIP), poor process parameter controllability is a significant challenge in uniform large-scale nanopatterning. Herein, we introduce a EHIP process using an ultrahigh electric field (>108 V/m) to effectively accelerate the pattern growth evolution. Owing to the strong dependence on a temporal parameter (1/τm) of the field strength, our method not only reduces the completion time of pattern growth but also overcomes critical parametric restrictions on the pattern replication, thereby enhancing the replicated pattern quality in three dimensions. The pattern can be uniformly replicated over the entire film surface even without a perfectly uniform air gap, which has been severely difficult in the conventional method. To further demonstrate how straightforward yet versatile our approach is, we applied our EHIP approach to successfully replicate the densely packed nanostructures of cicada wings.

Overview of the design of bionic fine hierarchical structures for fog collection

Nature always uses its special wisdom to construct elegant and suitable schemes. Consequently, organisms in the flora and fauna are endowed with fine hierarchical structures (HS) to adapt to the harsh environment due to many years of evolution. Water is one of the most important resources; however, easy access to it is one the biggest challenges faced by human beings. In this case, fog collection (FC) is considered an efficient method to collect water, where bionic HS can be the bridge to efficiently facilitate the process of the FC. In this review, firstly, we discuss the basic principles of FC. Secondly, the role of HS in FC is analyzed in terms of the microstructure of typical examples of plants and animals. Simultaneously, the water-harvesting function of HS in a relatively new organism, fungal filament, is also presented. Thirdly, the HS design in each representative work is analyzed from a biomimetic perspective (single to multiple biomimetic approaches). The role of HS in FC, and then the FC performance of each work are analyzed in order of spatial dimension from a bionic perspective. Finally, the challenges at this stage and the outlook for the future are presented.

Pattern formation in thin polymeric films via electrohydrodynamic patterning

The free surface of a thin polymeric film is often unstable and deforms into various micro-/nano-patterns under an externally applied electric field. This paper reviews a recent patterning technique, electrohydrodynamic patterning (EHDP), a straightforward, cost-effective and contactless bottom-up method. The theoretical and numerical studies of EHDP are shown. How the characteristic wavelength and the characteristic time depend on both the external conditions (such as voltage, film thickness, template-substrate spacing) and the initial polymer properties (such as rheological property, electrical property and surface tension) is theoretically and experimentally discussed. Various possible strategies for fabricating high-aspect-ratio or hierarchical patterns are theoretically and experimentally reviewed. Aligning and ordering of the anisotropic polymers by EHDP is emphasized. A perspective, including novelty and limitations of the methods, particularly in comparison to some conventional patterning techniques, and a possible future direction of research, is presented.