Abstract Droplet transport still faces numerous challenges, such as a limited transport distance, large volume loss, and liquid contamination. Inspired by the principle of ‘synergistic biomimetics’, we propose a design for a platform that enables droplets to be self-propelled. The orchid leaf-like three-dimensional driving structure provides driving forces for the liquid droplets, whereas the lotus leaf-like superhydrophobic surface prevents liquid adhesion, and the bamboo-like nodes enable long-distance transport. During droplet transport, no external energy input is required, no fluid adhesion or residue is induced, and no contamination or mass loss of the fluid is caused. We explore the influence of various types and parameters of wedge structures on droplet transportation, the deceleration of droplet speed at nodal points, and the distribution of internal pressure. The results indicate that the transport platform exhibits insensitivity to pH value and temperature. It allows droplets to be transported with varying curvatures in a spatial environment, making it applicable in tasks like target collection, as well as load, fused, anti-gravity, and long-distance transport. The maximum droplet transport speed reached (58 ± 5) mm·s −1 , whereas the transport distance extended to (136 ± 4) mm. The developed platform holds significant application prospects in the fields of biomedicine and chemistry, such as high-throughput screening of drugs, genomic bioanalysis, microfluidic chip technology for drug delivery, and analysis of biological samples.
Selective fabrication of superhydrophilic (S-philic) region on a superhydrophobic (S-phobic) surface requires complex technology and high cost, which has limited applications of extreme wettability patterns. In this paper, a twice-chemical-etching approach without special modification is used to prepare the extreme wettability patterns. Superhydrophobicity and superhydrophilicity can be successfully achieved after twice chemical etching for 20 seconds. The obtained patterns can maintain their extreme wettability for at least 30 days. Functional platforms with single-S-philic and multi-S-philic regions are fabricated to manipulate water and various organic liquids with water-film protection in an air environment.
Abstract Stimuli‐responsive patterned photonic actuators, characterized by their patterned nano/microscale structures and capacity to demonstrate synergistic color changes and shape morphing in response to external stimuli, have attracted intense scientific attention. However, traditional patterned photonic actuator systems still face limitations such as cumbersome and time‐consuming preparation processes and small‐scale deformations. Herein, we introduce a facile approach involving an athermal embossing technique to rapidly fabricate patterned photonic actuators based on near‐infrared (NIR) light‐responsive liquid crystal elastomers. The resulting patterned photonic actuators demonstrate remarkable features, including brilliant angle‐dependent structural color, complex three‐dimensional actuation, and good color durability under NIR light stimulation. As illustrative demonstrations of the proof‐of‐concept, we fabricate two light‐fuelled patterned photonic soft actuators: a butterfly‐inspired actuator that can produce wing‐flapping dynamic changes in structural color, and an origami crane‐shaped actuator with shape memory, structural color information storage, and dynamic display properties. This strategy provides distinct insights into the design and fabrication of various patterned photonic soft robotic devices and intelligent actuators.
Abstract Two‐dimensional layered ammonium vanadium oxalate‐phosphates (AVOPh) with the structural formula of (NH 4 ) 2 [VO(HPO 4 )] 2 (C 2 O 4 )·5H 2 O are synthesized though a hydro‐thermal method, which is dispersed into poly(vinyl alcohol) (PVA) matrix to prepare PVA/AVOPh composites. The results of thermal analysis indicate that AVOPh and PVA have similar decomposition temperature from 280 to 500°C, which is critical for choosing flame retardant. The incorporation of AVOPh significantly improves the thermal stability and flame retardancy of PVA/AVOPh composites that the T 5% value of PVA/2 wt% AVOPh composites is up to 215°C, and the residue of PVA/8 wt% AVOPh composites is enhanced to 16.9%, while those of pure PVA are only 178°C and 2.4%. PVA/4 wt% AVOPh composites can pass V‐0 level, and its limiting oxygen index value is up to 32.0%. Furthermore, the peak heat release rate (PHRR) and total heat release (THR) of PVA/AVOPh composites are obviously decreased, which reduced by 43.4% and 43.8% with the addition of 4 wt% AVOPh, compared with those of pure PVA. The excellent thermal stability and flame retardancy are mainly attributed to the uniform dispersion and barrier effect of 2D layered AVOPh, the release of crystal water, ammonia and phosphorus free radicals and the two‐phase flame retardant catalytic mechanism of vanadium and phosphorus.
Marine oil spills seriously endanger sea ecosystems and coastal environments, resulting in a loss of energy resources. Environmental and economic demands emphasize the need for new methods of effectively separating oil-water mixtures, while collecting oil content at the same time. A new surface-tension-driven, gravity-assisted, one-step, oil-water separation method is presented for sustained filtration and collection of oil from a floating spill. A benchtop prototype oil collection device uses selective-wettability (superhydrophobic and superoleophilic) stainless steel mesh that attracts the floating oil, simultaneously separating it from water and collecting it in a container, requiring no preseparation pumping or pouring. The collection efficiencies for oils with wide ranging kinematic viscosities (0.32-70.4 cSt at 40 °C) are above 94%, including motor oil and heavy mineral oil. The prototype device showed high stability and functionality over repeated use, and can be easily scaled for efficient cleanup of large oil spills on seawater. In addition, a brief consolidation of separation requirements for oil-water mixtures of various oil densities is presented to demonstrate the versatility of the material system developed herein.
Abstract The effect of post-heat treatment on the microstructure and microhardness of laser cladded high Co-Ni secondary hardening steel coating was investigated. The microstructures were analyzed using a SEM equipped with an EDS, and the microhardness was measured with a Vickers indenter. Decomposition of the retained austenite in the coating occurred during the post-heat treatment. As the temperature increased from 200 °C to 600 °C, the quantity of the retained austenite at the boundaries decreased significantly, while that of the needle-shaped M 3 C cementite and M 2 C carbides increased. The M 2 C carbides evidently coarsened when the temperature was higher than 500 °C. The microhardness of high Co-Ni steel coating increased as the temperature of post-heat treatment increased from 200 °C to 400 °C because the fine-scale M 2 C carbides were coherent with the matrix and increased distinctly in this temperature range. It decreased sharply when the temperature further increased from 500 °C to 600 °C due to both the incoherency of the coarsened M 2 C carbides and the recovery of dislocations in the carbon-supersaturated matrix.
Events number and 3D location distribution of Acoustic Emission (AE) are first-hand data for rock damage evolution process. It is widely used in geotechnical engineering disaster prediction and structural failure monitoring. By analyzing the destroy condition and mechanical property in simulating the axial compression test, it was found that the variation trend of acoustic emission obtained from the simulation was similar to the actual rock specimen. The total process includes four stages, namely: initial phase, premonition phase, damage phase, and residual phase. Through the simulation analysis of the fractured rock specimen, it can be found that the crack direction has a strong relationship with the internal damage of specimen. The weak surface along the shear direction has a great impact to the strength of the rock specimen which is key point in monitor. Along the axial weak surface, the inner destruction of rock specimen is more complex. In the early damage stage, the destruction is similar to the dense rock. In post stage, the rock damage along the fracture angle and weak surface.
Plasma hydrophilization is a general method to increase the surface free energy of materials. However, only a few works about plasma modification focus on the hydrophilization of tube inner and outer walls. In this paper, we realize simultaneous and long-lasting plasma hydrophilization on the inner and outer walls of polytetrafluoroethylene (PTFE) tubes by atmospheric pressure plasmas (APPs). Specifically, an Ar atmospheric pressure plasma jet (APPJ) is used to modify the PTFE tube's outer wall and meanwhile to induce transferred He APP inside the PTFE tube to modify its inner wall surface. The optical emission spectrum (OES) shows that the plasmas contain many chemically active species, which are known as enablers for various applications. Water contact angle (WCA) measurements, x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) are used to characterize the plasma hydrophilization. Results demonstrate that the wettability of the tube walls are well improved due to the replacement of the surface fluorine by oxygen and the change of surface roughness. The obtained hydrophilicity decreases slowly during more than 180 d aging, indicating a long-lasting hydrophilization. The results presented here clearly demonstrate the great potential of transferring APPs for surface modification of the tube's inner and outer walls simultaneously.
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