Anisotropic Superhydrophobic Properties Replicated from Leek Leaves

A bio-inspired approach to fabricate robust superhydrophobic (SHB) surfaces with anisotropic properties replicated from a leek leaf is presented. The polydimethylsiloxane (PDMS) replica surfaces exhibit anisotropic wetting, anti-icing, and light scattering properties due to microgrooves replicated from leek leaves. Superhydrophobicity is achieved by a novel modified candle soot (CS) coating that mimics leek's epicuticular wax. The resulting surfaces show a contact angle (CA) difference of ≈30° in the directions perpendicular and parallel to the grooves, which is similar to the anisotropic properties of the original leek leaf. The coated replica is durable, withstanding cyclic bending tests (up to 10 000 cycles) and mechanical sand abrasion (up to 60 g of sand). The coated replica shows low ice adhesion (10 kPa) after the first cycle; and then, increases to ≈70 kPa after ten icing-shearing cycles; while, anisotropy in ice adhesion becomes more evident with more cycles. In addition, the candle soot-coated positive replica (CS-coated PR) demonstrates a transmittance of ≈73% and a haze of ≈65% at the wavelength of 550 nm. The results show that the properties depend on the replicated surface features of the leek leaf, which means that the leek leaf appears to be a highly useful template for bioinspired surfaces.

Looking for future biological control agents: the comparative function of the deutosternal groove in mesostigmatid mites

The physics of fluid laminar flow through an idealised deutosternum assembly is used for the first time to review predatory feeding designs over 72 different-sized example species from 16 mesostigmatid families in order to inform the finding of new biological control agents. Gnathosomal data are digitised from published sources. Relevant gnathosomal macro- and micro-features are compared and contrasted in detail which may subtly impact the control of channel- or 'pipe'-based transport of prey liquids around various gnathosomal locations. Relative deutosternal groove width on the mesostigmatid subcapitulum is important but appears unrelated to the closing velocity ratio of the moveable digit. Big mites are adapted for handling large and watery prey. The repeated regular distance between deutosternal transverse ridges ('Querleisten') supports the idea of them enabling a regular fluctuating bulging or pulsing droplet-based fluid wave 'sticking' and 'slipping' along the groove. Phytoseiids are an outlier functional group with a low deutosternal pipe flow per body size designed for slot-like microchannel transport in low volume fluid threads arising from daintily nibbling nearby prey klinorhynchidly. Deutosternal groove denticles are orientated topographically in order to synergise flow and possible mixing of coxal gland-derived droplets and circumcapitular reservoir fluids across the venter of the gnathosomal base back via the hypostome to the prey being masticated by the chelicerae. As well as working with the tritosternum to mechanically clean the deutosternum, denticles may suppress fluid drag. Shallow grooves may support edge-crawling viscous flow. Lateral features may facilitate handling unusual amounts of fluid arising from opportunistic feeding on atypical prey. Various conjectures for confirmatory follow-up are highlighted. Suggestions as to how to triage non-uropodoid species as candidate plant pest control agents are included.

Effect of Hydrophobic Nano-SiO2 Particle Concentration on Wetting Properties of Superhydrophobic Surfaces

As a unique surface wettability, superhydrophobicity has great application value. A variety of preparation methods for superhydrophobic surfaces have been reported, which have the disadvantages of high cost and complicated process. In order to design a method that is easy to operate, low-cost, and suitable for large-scale preparation of superhydrophobic surfaces, in this paper, hydrophobic nano-SiO₂ particles are used as spray fillers, and superhydrophobic surfaces are successfully obtained by the spraying process. According to the classical Cassie and Wenzel theory, the influence of the concentration change of hydrophobic nano-SiO₂ particles on their wettability is explained, and the appropriate spray concentration parameters are obtained. The results show that the proportion of hydrophobic nano-SiO₂ particles is lower than 0.05 g/mL, which will lead to insufficient microstructure on the surface of the coating, and cannot support the droplets to form the air bottom layer. However, an excessively high proportion of hydrophobic nano-SiO₂ particles will reduce the connection effect of the silicone resin and affect the durability of the surface. Through theoretical analysis, there are Wenzel state, tiled Cassie state, and stacked Cassie state in the spraying process. When the substrate surface enters the Cassie state, the lower limit of the contact angle is 149°. This study has far-reaching implications for advancing the practical application of superhydrophobic surfaces.

Dust proof properties of spinodal porous surfaces

With an aim of dust proof in optical coating, contact force with spinodal porous surfaces was investigated by counting the number of particles after exposure to a practical circumstance and by directly measuring the contact forces with a probe of Au sphere using an atomic force microscope (AFM). The interaction between the oiled particles and the porous surface was also investigated on an antireflection coating using greases containing particles of polytetrafluoroethylene (PTFE). It was found that the porous structure played the role of adsorbing oil and lowering the contact force between the particles and the surface without deterioration of the antireflection. The contact force was treated based on the liquid bridges between the particles and the surface, and the contribution from the term of Laplace pressure is inferred to be lowered due to the reduced width of the silica skeletons.

Superhydrophobic Ni-Reduced Graphene Oxide Hybrid Coatings with Quasi-Periodic Spike Structures

Recently, sophisticated technologies are applied to design a certain surface nature that can have superhydrophobic properties. Thus, a simple spray technique was introduced to prepare a superhydrophobic surface using rGO with Ni-S system (rGO-Ni) by using NiSO4 catalyst under microwave irradiation at various reaction times of 5, 10, 20, and 30 min. The GO reduction was conducted at a fixed Ar/H2 ratio, a flow rate of 0.4 L/min, microwave power of 720 W, and a mass of 0.5 g. GO powder with nickel sulfate catalyst was treated under Ar/H2 (4:1) mixture for GO reduction, where Ar and H2 were expected to prevent the rebinding of oxygen released from GO. The result of XRD and Raman measurement confirms that rGO-Ni prepared at reaction time 20 min exhibit the highest reduction of GO and the presence of various Ni-S crystal structures such as NiS, NiS2, Ni3S2, and Ni3S4 due to decomposition of NiSO4. The rGO-Ni coating performance shows superhydrophobic nature with a contact angle of 150.1°. The AFM images show that the addition of nickel to rGO produces a quasi-periodic spike structure, which increases the superhydrophobicity of the r-GO-Ni coated glass with a contact angle of 152.6°. It is emphasized that the proposed simple spray coating using rGO-Ni provides a more favorable option for industry application in obtaining superhydrophobic surfaces.

A review: progress in preventing tissue adhesions from a biomaterial perspective

Postoperative adhesions (POA) are one of the main problems suffered by patients and are a common complaint. It is considered to be closely associated with the healing mechanism of damaged tissues. Tissue adhesions accompany other symptoms such as inflammation, pain, and even dyskinesia under certain conditions, compromising the patients' quality of life. On the other hand, common treatments involve high costs, re-surgery or long-term hospital stays. Therefore, alternative approaches need to be formulated so that aforementioned problems can be resolved. To this end, a review of recent advances in this context is imperative. In this review, we have highlighted the mechanism of adhesion formation, advances in common therapeutic approaches, and prospective treatments in preventing tissue adhesions. Based on the literature, it can be determined that the disadvantages of available commercial products in the treatment of tissue adhesion have led researchers to utilize alternative methods for designing anti-adhesive products with different structures such as electrospun fibrous mats, hydrogels, and nanospheres. These studies are on the fast track in producing optimal anti-adhesion materials. We hope that this article can attract attention by showing various mechanisms and solutions involved in adhesion problems and inspire the further development of anti-adhesion biomaterials.