Localized electrodeposition micro additive manufacturing of pure copper microstructures

The fabrication of pure copper microstructures with submicron resolution has found a host of applications,such as 5G communications and highly sensitive detection.The tiny and complex features of these structures can enhance device performance during high-frequency operation.However,manufacturing pure copper microstructures remain challenging.In this paper,we present localized electrochemical deposition micro additive manufacturing(LECD-μAM).This method combines localized electrochemical deposition(LECD)and closed-loop control of atomic force servo technology,which can effectively print helical springs and hollow tubes.We further demonstrate an overall model based on pulsed microfluidics from a hollow cantilever LECD process and closed-loop control of an atomic force servo.The printing state of the micro-helical springs can be assessed by simultaneously detecting the Z-axis displacement and the deflection of the atomic force probe cantilever.The results showed that it took 361 s to print a helical spring with a wire length of 320.11μm at a deposition rate of 0.887μm s^(-1),which can be changed on the fly by simply tuning the extrusion pressure and the applied voltage.Moreover,the in situ nanoindenter was used to measure the compressive mechanical properties of the helical spring.The shear modulus of the helical spring material was about 60.8 GPa,much higher than that of bulk copper(~44.2 GPa).Additionally,the microscopic morphology and chemical composition of the spring were characterized.These results delineate a new way of fabricating terahertz transmitter components and micro-helical antennas with LECD-μAM technology.

Analytical Solution for an Elastic Sphere Indenting a Layered Half-Space

The contact problem for the elastic sphere indenting a layered half-space is considered. Analytical methods for solving this problem have been developed on the basis of the 3-D fundamental solution of a half space with a single coating layer under a normal concentrated force on the surface. The normal pressure distribution within the contact zone is assumed as Hertzian type. The solutions are constructed using superposition principle in the form of infinite series. Through comparing with the numerical results of FEM,it can be verified that the exact solutions have a rapid convergence rate and the stresses and displacements are mainly determined by the first term,which is corresponding to the solution of homogeneous half-space under Hertzian loading. The contact radius can be predicted applying the method.

Effect of Plastocene Embedment in the Microperforated Plate on Its AcousticPerformance

Noise pollution is one of the contemporary environmental pollution, which seriously damages people’s green andhealthy life. In order to further improve the low frequency sound absorption performance of microperforatedpanel (MPP), a new plastocene coupled microperforated plate (PCMPP) is proposed. The acoustic propertiesof PCMPP with different apertures and perforation ratio were measured by transfer function method and compared with that of conventional MPPs. It is found that when the aperture was 0.8 mm, the peak value of soundabsorption coefficient of PCMPP decreased by 150 Hz compared with MPP. In a certain range, PCMPP with larger apertures showed a greater influence on sound absorption property in low frequency. In addition, higher perforation ratio led to a greater PCMPP bandwidth of sound absorption. On the other hand, the effect of PCMPPwith aperture of 0.2 mm on the performance of MPP was reduced, which could be compensated by increasing theperforation ratio. Furthermore, we found that the effect of aperture, perforation ratio and cavity on the soundabsorption performance of PCMPP was consistent with that of ideal rigid MPP. The step cooling curve showedthat the plastocene began to soften at about 50℃, representing a great potential for a non-high temperaturework environment.

Recent progress in bio-inspired macrostructure array materials with special wettability—from surface engineering to functional applications

Bio-inspired macrostructure array(MAA,size:submillimeter to millimeter scale)materials with special wettability(MAAMs-SW)have attracted significant research attention due to their outstanding performance in many applications,including oil repellency,liquid/droplet manipulation,anti-icing,heat transfer,water collection,and oil–water separation.In this review,we focus on recent developments in the theory,design,fabrication,and application of bio-inspired MAAMs-SW.We first review the history of the basic theory of special wettability and discuss representative structures and corresponding functions of some biological surfaces,thus setting the stage for the design and fabrication of bio-inspired MAAMs-SW.We then summarize the fabrication methods of special wetting MAAs in terms of three categories:additive manufacturing,subtractive manufacturing,and formative manufacturing,as well as their diverse functional applications,providing insights into the development of these MAAMs-SW.Finally,the challenges and directions of future research on bio-inspired MAAMs-SW are briefy addressed.Worldwide efforts,progress,and breakthroughs from surface engineering to functional applications elaborated herein will promote the practical application of bio-inspired MAAMs-SW.

Biomimetic Superlyophobic Metallic Surfaces: Focusing on Their Fabrication and Applications

Metals are indispensable engineered materials for day-to-day life.Researches focused on metallic surfaces with superlyophobicity(superhydrophobicity,superoleophobicity,underwater superoleophobicity and slippery characteristic)have attracted much attention recently.Nature is a magician that gives each organic life a unique advantage.Researchers have created a large number of biomimetic superlyophobic metallic surfaces through various approaches.These biomimetic superlyophobic metallic surfaces exhibit advantages in many applications,such as self-cleaning,corrosion resistance,anti-icing,and drag reduction.In this review,the specific fabrication and applications of biomimetic superlyophobic metallic surfaces were reported.The remaining challenges and future outlook of biomimetic superlyophobic metallic surfaces were preliminarily analyzed.It is hoped that the review will be essential for broadening the scope of potential applications of metals and providing a powerful reference for future research on metal-based advanced functional materials.

Bioinspired materials for droplet manipulation:Principles,methods and applications

Droplet manipulation techniques such as transport and merging have been widely used in many fields including biology,chemistry,material and energy applications.Moreover,droplet manipulation strategies have been extensively investigated and reviewed in terms of droplet placement on solid surfaces.However,less attention has been paid to the practice of droplet manipulation technology in other environments,limiting our understanding and the broadening of technology application.In this article,we provided an overview of the recent progress in controlling droplets in various situations,including droplet manipulation on a surface mediated by the passive strategy(Laplace pressure and wettability gradients)and active strategy(electric field,magnetic field,light and heat).We also presented the principle of droplet manipulation and detailed the application of bionic surfaces in droplet manipulation,and the applications and prospects of droplet manipulation technology were summarized.

Research Progress on Corrosion Resistance of Magnesium Alloys with Bio-inspired Water-repellent Properties:A Review

Thanks to its excellent mechanical properties,magnesium alloys have many potential applications in the aerospace and other fields.However,failure to adequately solve corrosion problems of magnesium alloy becomes one of the factors restricting its wide use in many industrial fields.Inspired by nature,researchers designed and fabricated bio-inspired water-repellent(superhydrophobic and slippery liquid-infused porous surface)surfaces with special wetting properties by exploring the surface microstructures of plants and animals such as lotus leaf and nepenthes pitcher,exhibiting excellent corrosion-resistant performance.This article summarizes the research progress on corrosion resistance of magnesium alloys with bio-inspired water-repellent properties in recent years.It mainly introduces the corrosion reasons,types of corrosion of magnesium alloys,and the preparation of magnesium alloys with bio-inspired water-repellent properties to improve corrosion resistance.In particular,it is widely used and effective to construct water-repellent and anti-corrosion coating on the surface of magnesium alloy by surface treatment.It is hoped that the research in this review can broaden the application range of magnesium alloys and provide a powerful reference for the future research on corrosion resistance of magnesium alloys.