Sliding friction and contact angle hysteresis of droplets on microhole-structured surfaces.

Microstructured surfaces with continuous solid topography have many potential applications in biology and industry. To understand the liquid transport property of microstructured surfaces with continuous solid topography, we studied the sliding behavior of a droplet on microhole-structured surfaces. We found that the sliding friction of the droplet increased with increasing solid area fraction due to enlarged apparent contact area and enhanced contact angle hysteresis. By introducing a correction factor to the modified Cassie-Baxter relation, we proposed an improved theoretical model to better predict the apparent receding contact angle. Our experimental data also revealed that the geometric topology of surface microstructures could affect the sliding friction with microhole-decorated surfaces, exhibiting a larger resistance than that for micropillar-decorated surfaces. Assisted by optical microscopy, we attributed this topology effect to the continuity and the true total length of the three-phase contact line at the receding edge during the sliding. Our study provides new insights into the liquid sliding behavior on microstructured surfaces with different topologies, which may help better design functional surfaces with special liquid transport properties.

Friction of Droplets Sliding on Microstructured Superhydrophobic Surfaces.

Liquid transport is a fundamental process relevant to a wide range of applications, for example, heat transfer, anti-icing, self-cleaning, drag reduction, and microfluidic systems. For these applications, a deeper understanding of the sliding behavior of water droplets on solid surfaces is of particular importance. In this study, the frictional behavior of water droplets sliding on superhydrophobic surfaces decorated with micropillar arrays was studied using a nanotribometer. Our experiments show that surfaces with a higher solid area fraction generally exhibited larger friction, although friction might drop when the solid area fraction was close to unity. More interestingly, we found that the sliding friction of droplets was enhanced when the dimension of the microstructures increased, showing a distinct size effect. The nonmonotonic dependence of friction force on solid area fraction and the apparent size effect can be qualitatively explained by the evolution of two governing factors, that is, the true length of the contact line and the coordination degree of the depinning events. The mechanisms are expected to be generally applicable for other liquid transport processes involving the dynamic motion of a three-phase contact line, which may provide a new means of tuning liquid-transfer behavior through surface microstructures.

[Characteristics of Fungi Community Structure and Genetic Diversity of Forests in Guandi Mountains].

Soil microorganisms drive the biogeochemical process of carbon, nitrogen, phosphorus and sulfur, and play a key role in maintaining soil carbon sink and ecosystem function. The study on effects of environmental and spatial factors on the structure of microbial community in boreal coniferous forest soil will provide theoretical basis for making management measures in local forest ecosystem. Our research analyzed five soil fungi communities (LpMC1, LpMC2, PwMC, PtMC, and BMC) in four forest types, including Larix principis-rupprechtii forest, Picea wilsonii forest, Pinus tabulaeformis forest and Betula spp. forest, respectively, in Pangquangou Nature Reserve in Guandi Mountains with Illumina high-throughput sequencing technology. Meanwhile, soil environmental factors and diversity of undergrowth plants were determined to analyze the relationship between fungi community structure and vegetation as well as soil environmental factors. The results showed that:①There were seven eumycota and thirty-three advantageous fungal genera in the five sample sites; ②Redundancy analysis results showed that soil pH, temperature, moisture, total nitrogen, the content of NH4+, total carbon, invertase activity, urease activity, undergrowth dominance and evenness were significantly associated with soil fungi community structure; ③Cluster analysis and principal component analysis showed that forest vegetation type, soil environmental factors and undergrowth had significant effects on soil fungi community structure; ④The results of PCNM analysis showed that at a local scale, dispersal limitation had no significant influence on fungi community structure in the study area. The forest soil fungi community structure in the study area was significantly affected by environmental selection (soil pH, temperature, moisture, total nitrogen, the content of NH4+, total carbon, invertase activity, urease activity, undergrowth dominance and evenness, forest type).

Guided Self-Propelled Leaping of Droplets on a Micro-Anisotropic Superhydrophobic Surface.

By introducing anisotropic micropatterns on a superhydrophobic surface, we demonstrate that water microdroplets can coalesce and leap over the surface spontaneously along a prescribed direction. This controlled behavior is attributed to anisotropic liquid-solid adhesion. An analysis relating the preferential leaping probability to the geometrical parameters of the system is presented with consistent experimental results. Surfaces with this rare quality demonstrate many unique characteristics, such as self-powered, and relatively long-distance transport of microdroplets by "relay" coalescence-induced leaping.

[Effects of organic manure on wheat growth under lead stress].

A pot experiment was conducted to study the effects of organic manure on the wheat growth under different levels of lead stress. With increasing lead stress level, whether fertilization or not, the plant height, shoot dry mass, adventitious root number, root total length, root dry mass, root activity, root total and active absorbing area, and root SOD and POD activities decreased, and root MDA content presented an increasing trend. The decrement of the above-mentioned parameters differed with fertilization treatments. Applying organic manure mitigated the impact of lead stress on wheat growth to some extent, delayed the senescence of wheat roots, and promoted root development and growth, ultimately leading to the increase of wheat yield and the decrease of lead content in grain.