Corrosion Resistance and Antifouling Bioinspired Coating with Doped Polyaniline and TO@CA Self-Healing Nanocapsules

In this study,an integrative bioinspired coating system for antifouling and corrosion resistance was investigated,in which self-healing nanocapsules(tung oil calcium alginate,TO@CA),doped polyaniline and nano-titanium dioxide nanocomposites(SPAn–TiO_(2))and a biostructure metal surface were combined.The antifouling property of the bioinspired coating resulted from the synergistic antifouling effect of nano-TiO_(2)and acid-doped polyaniline in SPAn–TiO_(2).The protonated nitrogen with a positive charge in SPAn–TiO_(2)and the intrinsic bactericidal property of nano-TiO_(2)could damage negatively charged single-celled chlorella,endowing the composite coating with good antifouling performance(less algae attached on the surfaces after a 90-day antifouling test and a conductivity test).The composite bioinspired coating had excellent corrosion resistance,which was due to the good synergistic anticorrosion barrier effect of SPAn–TiO_(2)with TO@CA nanocapsules and the repairing ability of microcracks of TO@CA nanocapsules during the corrosion process.The bioinspired coating with 2 wt%SPAn–TiO_(2)and 2 wt%TO@CA nanocapsules exhibited a better adhesion,corrosion resistance and antifouling performance than the other coatings did.

Comparative study on heat transfer enhancement of metal foam and fins in a shell-and-tube latent heat thermal energy storage unit

Metal foam and fins are two popular structures that are employed to enhance the heat transfer of phase change materials in shell-and-tube heat storage units.However,it remains unclear which structure is better in terms of energy storage performance.In this study,the heat transfer enhancement performances of metal foam and fins are compared to provide guidance on the optimal structure to be chosen for practical applications.Three fin structures(four fins,two vertical fins,and two horizontal fins)are considered.Under the full configuration(volume fraction of metal=3%),the unit with four fins was found to have a faster melting rate than those with vertical or horizontal fins.In other words,increasing the number of fins helps to accelerate the melting process.Nevertheless,the unit with metal foam enhancement has the highest melting rate.Under the half configuration(volume fraction of metal=1.5%),the melting rate of the unit enhanced by metal foam is significantly decreased,whereas there is no remarkable changes in the units enhanced by fins.However,metal foam is still shown to be the best thermal enhancer.The energy storage rate of the unit enhanced by metal foam can be up to 10 times higher than that of the unit enhanced by fins.

“偷师”大自然:仿生海洋防污技术

海洋生物污损指的是海洋中的细菌、藻类、藤壶等在水下表面附着和生长的一种现象[1].生物污损会增加船体阻力、加速表面腐蚀、破坏螺旋桨,导致额外的油耗和过高的维护成本.额外的油耗加剧了CO2、SO2等气体的过量排放,影响各国政府对"碳中和"目标的实现.海洋生物污损还对跨海大桥、钻井平台、养殖网箱、海底管道等多种水下设施具有负面影响[2].据统计,海洋生物污损每年给全球海洋工业造成的损失超过150亿美元[3].传统的防污涂层一般通过释放有毒物质(例如氧化铜、三丁基锡等)杀死污损生物来达到防污效果.

Bio-inspired Graphene-enhanced Thermally Conductive Elastic Silicone Rubber as Drag Reduction Material

This study presented a graphene platelet/silicone rubber （GPL/SR） composite as a drag reduction material, inspired by the boundary heating drag reduction mechanism of dolphin skin. Graphene was added as a thermally conductive filler at weight fractions of 0.17 wt%, 0.33 wt% and 0.67 wt% to pristine silicone rubber （PSR）. Tests of the thermal conductivity and tensile properties showed that the thermal conductivity of all three GPL/SR materials of 0.17 wt%, 0.33 wt% and 0.67 wt% graphene were 20%, 40% and 50% higher than that of the P SR, respectively, and the elastic modulus of the 0.17 wt% GPL/SR materials was lowest. Droplet velocity testing, which can reflect the drag reduction mechanism of the heating boundary controlled by the GPL/SR composite, was performed between 0.33 wt% GPL/SR, which typically exhibits good mechanical properties and thermal conductivity performance, and the PSR. The results showed that on the 0.33 wt% GPL/SR, the droplet velocity was higher and the rolling angle was lower, implying that the GPL/SR composite had a drag-reducing function. In terms of the drag reduction mechanism, the heat conductivity performance of the GPL/SR accelerated the heat transfer between the GPL/SR composite surface and the droplet. The forces between the molecules decreased and the droplet dynamic viscosity was reduced. The drag of a sliding water droplet was proportional to the dynamic viscosity, which resulted in drag reduction. The application of GPL/SR material to the control fluid medium should have important value for fluid machinery.

Antifouling Technology Trends in Marine Environmental Protection

Marine fouling is a worldwide problem,which is harmful to the global marine ecological environment and economic benefits.The traditional antifouling strategy usually uses toxic antifouling agents,which gradually exposes a serious environmental problem.Therefore,green,long-term,broad-spectrum and eco-friendly antifouling technologies have been the main target of engineers and researchers.In recent years,many eco-friendly antifouling technologies with broad application prospects have been developed based on the low toxicity and non-toxicity antifouling agents and materials.In this review,contemporary eco-friendly antifouling technologies and materials are summarized into bionic antifouling and non-bionic antifouling strategies(2000-2020).Non-bionic antifouling technologies mainly include protein resistant polymers,antifoulant releasing coatings,foul release coatings,conductive antifouling coatings and photodynamic antifouling technology.Bionic antifouling technologies mainly include the simulated shark skin,whale skin,dolphin skin,coral tentacles,lotus leaves and other biology structures.Brief future research directions and challenges are also discussed in the end,and we expect that this review would boost the development of marine antifouling technologies.

Bio-inspired Superhydrophobic Self-healing Surfaces with Synergistic Anticorrosion Performance

The past decade has witnessed significant efforts in addressing the global metallic corrosion challenge,with a focus on avoiding or mitigating huge economic losses incurred by corrosion and on the development of protective coatings on metals.Herein,a synergistic anticorrosion coating with both superhydrophobicity and self-healing properties was reported,through a facile replica molding method by mixing the polyvinylidene fluoride(PVDF)matrix with nano-sized SiO2 particles and 2-mercaptobenzothiazole(MBT)loaded halloysites(HNTs).The surface exhibits robust self-cleaning behavior under harsh conditions and high liquid repellence to withstand the osmosis of corrosive ions.The self-healing performance of the coating,due to the introduction of MBT-loaded HNTs,enhances the anticorrosion capability,which is still valid once the protective layer is damaged.Potentiodynamic polarization(PDP)and Electrochemical Impedance Spectroscopy(EIS)measurements demonstrate that the synergetic effects in anticorrosion performances significantly enhance the long-term corrosion protection of metals.Hence,this type of dual-action coating may find unique applications in metal corrosion resistance where both super-repellency and self-healing properties are desired.

Novel Anti-fouling Strategies of Live and Dead Soft Corals(Sarcophyton trocheliophorum):Combined Physical and Chemical Mechanisms

At present,biomimetic antifouling research objects are mostly concentrated on the fast-moving marine organism,but the anti-fouling effect of the low-speed or static marine equipment is not obvious.This paper describes the anti-fouling mechanism of soft coral(Sarcophyton trocheliophorum),including the physical defense mechanism and the bactericidal ability of mucus and coral powder.As a sessile organisms,soft coral lacks escape mechanism.Therefore,the study on its antibacterial strategy is significant because it can provide theoretical guidance for static antifouling.Results showed that the live soft coral would molt in unfriendly environment,and the secreted mucus could defend themselves against fouling microorganism.Then,Liquid Chromatography-Mass Spectrometry(LC-MS)analysis was conducted to identify the bioactive compounds of the coral powder and mucus.Results revealed that both powder and mucus contained a wide variety of toxic components,which had bactericidal effects.Moreover,at the same concentration,the inhibitory effect of the main components on Gram-negative bacteria was stronger than that on positive bacteria.These findings enhance the understanding about the antifouling mechanism of soft coral and provide new ideas for design and prepare novel antifouling strategy to combat biofouling under static condition.

Epidermal radio frequency electronics for wireless power transfer

Epidermal electronic systems feature physical properties that approximate those of the skin,to enable intimate,long-lived skin interfaces for physiological measurements,human–machine interfaces and other applications that cannot be addressed by wearable hardware that is commercially available today.A primary challenge is power supply;the physical bulk,large mass and high mechanical modulus associated with conventional battery technologies can hinder efforts to achieve epidermal characteristics,and near-field power transfer schemes offer only a limited operating distance.Here we introduce an epidermal,farfield radio frequency(RF)power harvester built using a modularized collection of ultrathin antennas,rectifiers and voltage doublers.These components,separately fabricated and tested,can be integrated together via methods involving soft contact lamination.Systematic studies of the individual components and the overall performance in various dielectric environments highlight the key operational features of these systems and strategies for their optimization.The results suggest robust capabilities for battery-free RF power,with relevance to many emerging epidermal technologies.

Rhodium-catalyzed formal[4+3]annulation reaction of N-methoxybenzamides with gem–difluorocyclopropenes:A combination of experimental and theoretical studies

A rhodium-catalyzed[4+3]cycloaddition reaction between N-methoxybenzamides and gem–difluorocyclopropenes is described.The reaction offers a mild and efficient approach towards the synthesis of fluorinated 2 H-azepin-2-ones with broad substrate scope.A consecutive HOAc-assisted C–N bond formation and fluorine elimination are involved as key steps for success as illustrated by detailed DFT studies.

Construction and application of bionic antifouling coatings inspired by soft coral

Marine biofouling will bring a series of environmental and social problems,which restrict the development and utilisation of marine resources.Therefore,how to prevent biofouling has become a global issue.With the exploration of antifouling methods,bionic antifouling technology with environmentally friendly,broad‐spectrum,and long‐term advantages has gradually attracted people's attention.Inspired by the antifouling strategy of soft coral(Sarcophyton trocheliophorum),the silicone rubber(RTV‐2)with similar elasticity to coral skin was selected as the substrate.The composite structure of the upper transparent layer and the lower porous layer was prepared by simulating the structure of soft coral as the structural factors of the bionic antifouling coatings.Meanwhile,several organic antifouling components with high content contained in soft coral were added to the transparent layer and porous layer,respectively,as the component factors of biomimetic coatings.The bionic antifouling coatings,which are highly consistent with the coral structure,obtained the best antifouling performance under static and dynamic conditions.The above results provide new ideas for the synthesis of environmentally friendly bionic antifouling coatings.

Moldable and transferrable conductive nanocomposites for epidermal electronics

Skin-inspired soft and stretchable electronic devices based on functional nanomaterials have broad applications such as health monitoring,human-machine interface,and the Internet of things.Solution-processed conductive nanocomposites have shown great promise as a building block of soft and stretchable electronic devices.However,realizing conductive nanocomposites with high conductivity,electromechanical stability,and low modulus over a large area at sub-100μm resolution remains challenging.Here,we report a moldable,transferrable,high-performance conductive nanocomposite comprised of an interpenetrating network of silver nanowires and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate).The stacked structure of the nanocomposite synergistically integrates the complementary electrical and mechanical properties of the individual components.We patterned the nanocomposite via a simple,low-cost micromolding process and then transferred the patterned large-area electrodes onto various substrates to realize soft,skin-interfaced electrophysiological sensors.Electrophysiological signals measured using the nanocomposite electrodes exhibit a higher signal-to-noise ratio than standard gel electrodes.The nanocomposite design and fabrication approach presented here can be broadly employed for soft and stretchable electronic devices.