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A bionic tactile device is designed for object surface texture recognition, taking inspiration from the microstructure of human fingerprints. The sense of touch in humans is achieved through the frictional vibration and generation of electrical potential signals by subcutaneous receptors. Constructing a tactile sensing device involves generating distinct signals upon interacting with different materials. The piezoelectric film PVDF is particularly suitable as a sensitive material for sensors due to its excellent flexibility, strong mechanical strength, excellent dynamic response and cost-effectiveness. This paper presents the design of a PVDF-based fingerprint-inspired tactile sensor capable of differentiating various textures. By combining the collected signals with machine learning algorithms, diverse textures can be effectively identified. To demonstrate the sensor's superior performance, two experiments were conducted—one focused on recognizing different material textures, and the other on recognizing Braille characters. The accuracy achieved in these experiments was 97.4% and 96.5%, respectively, highlighting the technology's significant potential in intelligent robotics and human-computer interaction. [Display omitted] • A bionic tactile sensor with three different layers were proposed. • Two types of texture datasets were representatively constructed for analytical study. • Some eigenvalue parameters combined with machine learning algorithms was used to achieve high recognition accuracy. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to improve the tribological performance of Babbitt alloy under oil lubricant condition. Thus, the surface was treated into oleophobic state by modifying with low surface energy fluorosilane (1H,1H,2H,2H-perfluorodecyltriethoxysilane). It is believed that the oleophobic surface offered excellent wear resistance of Babbitt-based tribo-pairs. Design/methodology/approach: By modifying the Babbitt alloy with low surface energy fluorosilane and measuring the oil contact angle, the wetting behavior was evaluated. Using Pin on Disk tribometer, the tribological properties of bare Babbitt and modified Babbitt were quantified. The samples after the friction test were characterized by scanning electron microscope (SEM) and the anti-wear performance was evaluated under dry and oil lubrication conditions. Findings: Results showed that oil contact angle of modified Babbitt was109° which was tripled compared to that of prime surface, which indicates the oleophobic behavior was greatly improved. Under dry conditions, the friction coefficient of the modified surface with different load conditions is slightly lower than that of the bare surface, while the friction coefficient of the modified surface under lubrication conditions is significantly decreased compared to that of the bare surface. Interestingly, under low load and high load, the wear rate of the modified Babbitt alloy surface is only 1/4 and 1/3 of that of the bare surface, respectively. Originality/value: The work proposed an effective method to improve the Babbitt tribological performances and will lighten future ideas for the Babbitt alloy bearing with high wear resistance, which is beneficial to improve the service life of sliding bearings and has huge promotion and application value in the manufacture of sliding bearings. [ABSTRACT FROM AUTHOR]

Maintaining the long-term stability of water repellency and antifouling remains a challenge. This study presents the fabrication of a solid sharkskin-inspired surface exhibiting superhydrophobic and antifouling properties by polydimethylsiloxane (PDMS) and zinc oxide (ZnO) nanostructures through the simple microcasting and hydrothermal methods. The ZnO grown under optimal reaction parameters showed a remarkable contact angle of 151°, signifying the emergence of superhydrophobicity. Furthermore, the ZnO/PDMS sharkskin surface was found to reduce drag by up to 12.2%. Notably, the bacterial adhesion was decreased on the sharkskin-like PDMS surface with ZnO nanostructures by 96.5% compared to smooth PDMS. This resulted from the combined antifouling effects of ZnO photocatalytic property and the microstructure-induced hydrophobicity. Additionally, the ZnO nanostructures demonstrated exceptional mechanical stability and robustness. [ABSTRACT FROM AUTHOR]

The transverse skin of dolphins exhibits a remarkable drag reduction effect. Although previous studies have identified the drag reduction effect of transverse grooves, no clear guidelines exist regarding the impact of groove parameters on turbulent drag reduction. Hence, this paper suggests a novel numerical study using the Reynolds-averaged Navier–Stokes method to investigate the influence of half-sine wave structure parameters on turbulent drag. The results showed that the aspect ratio of shape parameters significantly affected the drag reduction rate by altering the flow velocity and drag distribution near the wall and increasing the viscous sublayer thickness. Moreover, a novel index friction pressure ratio F P r was introduced to evaluate the drag reduction. It was revealed that the ratio F P r was stable at optimal drag reduction effect regardless of the velocity. By optimizing the F P r , a maximum drag reduction of 29.3% was achieved. These findings provide insight for optimizing transverse groove in drag-reducing surface applications. [ABSTRACT FROM AUTHOR]

The tribological behaviors of soft materials are closely related to their surface chemistry and morphology. Thus, this study investigates the effects of surface chemistry and morphology on the stick-slip friction of polydimethylsiloxane (PDMS). Air plasma treatment is conducted to modify the surface chemistry, and the bionic shark skin texture is replicated on PDMS. The synergistic effect of the bionic shark skin texture and air plasma treatment on stick-slip friction is evaluated. The results show that air plasma treatment and bionic texture decrease the friction force. Various stick-slip features are observed under different numbers of pendant chains at the contact interfaces, which increase the adhesion force. This study provides fundamental insights into the stick-slip behaviors of other soft materials. [Display omitted] • Stick-slip patterns were proposed to analyze the stick-slip friction behavior of soft material such as PDMS. • Air plasma treatment was used to change surface chemistry of PDMS and decrease the friction of PDMS. • Bionic (shark skin) structure was replicated on PDMS to reduce the friction force and stick-slip effect. • Synergistic effect of surface chemistry and topography on friction of PDMS is analyzed and explained. [ABSTRACT FROM AUTHOR]

Abstract Agarose hydrogel as an efficient carrier for protein model has been considered to optimize the lubrication of artificial hip joints. Elevating the effectiveness of lubricant to reduce frictional coefficient and wear debris to prolong life time of prosthesis is a main goal. Various biological solvents, such as sodium chloride (NaCl) solution, simulated body fluid (SBF), phosphate buffer solution (PBS) and deionized water, have been investigated to achieve the best structure for polymeric network during the hydrogel preparation process. Results proof that SBF is able to provide sustained release with 38% reduction rate of frictional coefficient to demonstrate sufficient strength of the polymer chains. Novelty of the present work is focusing on the anti-friction performance of hydrogel protein delivery system designed for medical or pharmaceutical applications. Highlights • Agarose hydrogel has been designed as an efficient carrier for protein model. • Hydrogel released protein will improve the lubrication of artificial hip joints. • Hydrogel mechanical behavior is function of the solvents ionic concentration. • Role of hydrogel pore distribution for sustainability of the network was analyzed. • Existence of essential ions for creating the self-lubrication film on ceramic surface. [ABSTRACT FROM AUTHOR]

A layer-by-layer deposition technique with grafting chitosan on the Co-Cr-Mo alloy was developed. The performance of tribology and biocompatibility were investigated under simulated conditions. Wettability of coating surface was super hydrophilic and the surface was in positive charge under the neutral solution, which was favored in water-based lubricating and adhesion of cells. By pin-on-disk tests, the chitosan coating surface exhibited lower friction coefficient under various sliding speed as compared with the uncoated substratum. A wear rate of 1.1 × 10 −7 mm 3 /Nm was detected, which was only one seventh of uncoated surfaces. Hypothetically illuminating the mechanism of antifriction is able to lead for better wear resistance. Co-culturing with osteoblast cells showed that coating had good benefits in the proliferation of osteoblast cells. [ABSTRACT FROM AUTHOR]

Surface texturing is one of the effective strategies to improve bioactivity of implantable materials. In this study, hierarchical micro and nano structure (HMN) were fabricated on Co–Cr–Mo alloy substrate by a movable picosecond laser irradiation. Respectively, microgrooves with nano ripples and islands were produced on Co–Cr–Mo alloy by low and high laser power density. X-ray diffraction apparatus (XRD) phase analysis illustrated that substrate was in the phase of γ- face-centered cubic structure (FCC) before laser treatment, while it was in ε-hexagonal closest packing structure (HCP) phase dominant after laser treatment. Cell adhesion and proliferation studies showed that the HMN surface exhibits enhanced adhesion of MC3TC-E1 osteoblast and promoted cell activity. Analyzing of the morphology of osteoblast cells indicated cells were in high ratio of elongation on the HMN surface, while they mainly kept in round shape on the polished surface. Results indicated the formation of hierarchical structure on Co–Cr–Mo alloy was able to improve biological performances, suggesting the potential application in cobalt based orthopedic implants. [ABSTRACT FROM AUTHOR]

This paper considers the problem of distributed formation control for a second-order multi-agent system with a directed communication topology and constant communication time delays. A distributed proportion–integration–derivation (DPID) formation control law is proposed for the multi-agent system by introducing the integration information of the formation errors. A delay-independent condition and two delay-dependent conditions on the asymptotical formation stability are respectively presented under the assumption of the communication topology containing a directed spanning tree. Based on the Nyquist stability criterion, the range of the feasible time delays for asymptotical formation stability is obtained by analyzing the relationship between the Nyquist curves and the unit circle. Finally, simulations illustrate the effectiveness of the theoretical results. [ABSTRACT FROM AUTHOR]

This paper presents a unified framework of fault diagnosis and fault-tolerant cooperative output regulation (FTCOR) for a linear discrete-time multi-vehicle system with sensor faults. The FTCOR control law is designed through three steps. A cooperative output regulation (COR) controller is designed based on the internal mode principle when there are no sensor faults. A sufficient condition on the existence of the COR controller is given based on the discrete-time algebraic Riccati equation (DARE). Then, a decentralised fault diagnosis scheme is designed to cope with sensor faults occurring in followers. A residual generator is developed to detect sensor faults of each follower, and a bank of fault-matching estimators are proposed to isolate and estimate sensor faults of each follower. Unlike the current distributed fault diagnosis for multi-vehicle systems, the presented decentralised fault diagnosis scheme in each vehicle reduces the communication and computation load by only using the information of the vehicle. By combing the sensor fault estimation and the COR control law, an FTCOR controller is proposed. Finally, the simulation results demonstrate the effectiveness of the FTCOR controller. [ABSTRACT FROM AUTHOR]

Recently, chitosan has become attractive due to being biodegradable, biocompatible and renewable. However, the weak mechanical properties of chitosan films limit their large-scale application. In this work, a strategy of blending TEMPO, oxidized CNF (TOCN) and chitosan was developed to fabricate nanocomposite films in order to improve the mechanical properties and maintain biocompatibility. The TOCN/chitosan nanocomposite films exhibited excellent optical transmittance (>85%) and extremely high tensile strength of 235 MPa. The good compatibility of TOCN and chitosan chains, good dispersion of chitosan aggregates and the presence of stiff TOCN crystal domains are the main reasons for getting improved mechanical strength of composite films. The films showed good biocompatible properties based on the cell activity assay results. Furthermore, they were stable in PBS buffer for more than 6 months without significant degradation. The TOCN/chitosan nanocomposite films with these excellent properties could be employed in medical applications. [Display omitted] • The CNF fibrils and chitosan chains show good intermixing. • The optical transparent films have high tensile strength. • The films have good biocompatible properties and stable in PBS buffer. [ABSTRACT FROM AUTHOR]

Among various surface modification technologies, laser surface texturing (LST) to introduce texture has attracted more scholars' attention for controlling the tribological performance. The enhanced processing quality of the textured surface results in reducing the coefficient of friction and improving the wear resistance. In this study, dielectric transformer oil was used to protect the surface of GCr15 bearing steel from undesired gases in the atmosphere during the laser processing. Three types of dimples, including circle, rectangle and hexagon, were ablated to evaluate their influence on friction and wear. It was found that LST with transformer oil greatly improved the surface texture processing quality, where the edges of dimples were effectively designed and burrs-free. Results showed that the depth of dimples was reduced up to 7%. Compared to the samples fabricated in air, the friction coefficient and the wear of improved surface were reduced up to 55% and 73.8%, respectively. This was attributed to the excellent shielding and coolant property of transformer oil. Additionally, the shapes of the dimples, the applied force and the sliding speed significantly affected the friction coefficient, where dimples operate as lubricant and debris stores. This study provides certain feasibility guidance for the tribological modification of GCr15 bearing material with oil method and expands its application on engineering surfaces. • Transformer oil-coated LST was introduced to improve the tribological properties. • Circular, rectangular and hexagonal dimples were studied. • LST with oil greatly improved the surface texture processing quality. • The friction and wear were reduced up to 55% and 73.8%, respectively. [ABSTRACT FROM AUTHOR]

Endowing coatings with effective protective function for metal substrates is of great interest. An excellent example is slippery liquid infused surface (SLIS) which possesses potential applications owing to its unique liquid repellency and self-cleaning properties. However, their widespread applications are facing obstacles of complex preparation, poor protection and low durability. Herein, a facile and efficient liquid infusion method was proposed to construct SLIS by altering the heterogeneous microstructure on the SiO x layer of the coatings with direct UV irradiation. The coatings were fabricated by conducting an appropriate UV irradiation treatment on polydimethylsiloxane (PDMS) film infused with methyl oleate (MO). The as-prepared transparent anti-fouling coatings showed outstanding anti-fouling properties against various contaminants such as algal (Chlorella), sand, rust (Fe 2 O 3), paints (both water-based and oil-based) and daily life liquid pollutants (e.g., water, coffee, cola, soy sauce and milk). In addition, results revealed that the coatings exhibited a prominent anti-corrosion performance. Moreover, the coatings had excellent mechanical, chemical and thermal durability regarding the great repellency of the pollutants. We proposed this synergistic strategy between lubricant infusion and coating heterogeneous microstructure to widen new possibilities for fabricating coatings with promissing anti-corrosive and anti-fouling functionality. [Display omitted] • A facile liquid infusion method was applied to fabricate slippery liquid infused surface (SLIS). • MO infused PDMS with 90 min UV-ray showed the greatest antifouling and anti-corrosion performance. • Outstanding mechanical, chemical and thermal durability were observed. [ABSTRACT FROM AUTHOR]

Slippery liquid infused porous surfaces (SLIPS) process potential applications in surface liquid repellency, self-cleaning and anti-adhesion, while exhibiting long-term and stable release of lubricants is remaining a great challenge. Herein, an efficient liquid injection method was proposed to construct SLIPS by altering the surface energy and adjusting the inner porous structure using the facile method of direct UV irradiation. The infusion efficiency and release behavior were significantly improved and verified with various techniques such as wetting measurement, confocal fluorescence microscopy and optical microscopy. It was found that the infusion and release behavior of lubricants were varied for different specimens with different UV irradiation time. Compared to the prime substrate, PDMS treated with 90 min UV irradiation showed the highest volume of lubricant penetration which was increased almost by 833 %. Additionally, the amount of infusion consisted with the surface energy and specimens with moderate wetting exhibited the most effective lubricating performance. For the sample with 90 min UV irradiation, an ultra-low friction coefficient of 0.018 was observed under water lubrication and its releasing could be detected even after a long period of 768 h. Our results provided a facile method for the future development of long-term lubricating surfaces which may broaden their applications in fields of anti-corrosion, anti-icing and anti-fog, anti-fouling, micro-flow control and oil-water ultra-slippery occasions. [Display omitted] • A facile and highly efficient liquid infusion method was fabricated to construct slippery liquid infused surface (SLIS). • PDMS treated with 90 min UV showed the highest volume of lubricant penetration which was increased almost by 833 %. • Ultra-low friction of coefficient (0.035) was observed for SLIPS under water lubricating. [ABSTRACT FROM AUTHOR]

The goal of the work is to investigate the lubrication mechanism of MoS 2 nano sheet. Polyisobutyleneamine Succinimide (PIBS) provides the steric repulsion to disperse nanoparticles in oil due to its long carbon chain. In the present study, the tribological behavior of nano-MoS 2 sheet mixed with different percentages of PIBS was explored. The dispersed state and the mode of nano-MoS 2 sheet entering the contact point were studied. Ball-on-disk results illustrated that the COF of nano-MoS 2 in paraffin oil with free of PIBS was 26.2% compared with those containing 3 wt% PIBS, and the reduction of wear depth reached 41.9%. The nano-MoS 2 sheets with 3 wt% PIBS were in discrete state in paraffin oil, which moved with side flow and could not enter the contact area to cause poor lubrication. Aggregation of particles took place in the case of low PIBS concentration and without PIBS, it entered the contact area and formed well-distributed MoS 2 tribofilm to reduce friction and wear. [ABSTRACT FROM AUTHOR]

Ship hulls and subsea equipment are plagued by current resistance, seawater particles impact, corrosion and other challenges in the ocean. Consequently, developing sustainable nontoxic antifouling coatings is highly urgent. Discoveries from nature have inspired us to design high-efficiency, environmentally friendly, and cost-effective antifouling coatings. In the study, a strategy of combining microstructures and Benzotriazole (BTA) was proposed through constructing shark skin shield scale structure, which improved drag reduction and increased abrasion resistance as well. On the synergistic effect of BTA as corrosion inhibitor, the friction coefficient of the coating was significantly reduced and the anti-corrosion performance was greatly improved. Compared to the smooth pure epoxy coating, the anti-corrosion performance and the drag reduction rate of Texture-BTA-3 % coating was improved by 30 % and about 10 %, respectively. Furthermore, the effect of coating structure on corrosion resistance was revealed. This investigation will broaden the applications in marine navigation with the favorable performance. [Display omitted] • A method for preparing epoxy resin with imitating sharkskin surface texture has been proposed. • Verified the influence of the coating texture on anti-corrosion performance. • Drag reduction rate of the designed coating in water is about 10 %. • The friction coefficient is reduced of 40 % during friction process. [ABSTRACT FROM AUTHOR]

Using the layer-by-layer deposition method, functional chitosan/casein phospopeptides (CS/CPP) composite coatings were produced on Co–Cr–Mo alloy. The CS/CPP composite coatings had the dendritic topography, and were quite hydrophilic. Zeta potential measurements showed the composite coatings were negative charged at neural pH. XPS results indicated that the CS/CPP composite coatings were covalently bond to the substrate. When MC3T3-E1 cells were seeded on the CS/CPP composite coatings, no cytotoxicity was observed. The bone morphogenetic protein-2 (BMP-2) mRNA expression was significantly up-regulated in MC3T3-E1 cells cultured on the composite coatings and it was twice as much as that of cells cultured on the bare substrate. The expression of osteoprotegerin (OPG) mRNA and the ratio of OPG/receptor activator of nuclear factor-κB ligand (RNAKL) mRNA were increased 5-fold and 55-fold, respectively. These results suggested the CS/CPP composite coatings may have potential application in cobalt matrix orthopaedic implants. [ABSTRACT FROM AUTHOR]

Osteoblast responses to Co-Cr-Mo alloy depend on not only the chemistry of alloy but also the physical properties of alloy surface, such as its microtopography and roughness. This study was undertaken to examine changes in cell adhesion, morphology, differentiation and gene expression during osteoblast interaction with different textured Co-Cr-Mo alloys. With laser surface texturing, three kinds of textured surfaces were fabricated. It showed that the microenvironment processed by laser surface texturing leads to an increase in surface roughness and DMEM contact angles of samples. Adhesion and differentiation tests demonstrated that osteoblast cells can discriminate surfaces with different roughness and surfaces with comparable roughness but different topographies such as triangle, circle and square textures. Morphological characteristics obtained by SEM imaging showed that osteoblast cells are elongated and are in polygonal shape on the textured surface. OPG/RANKL mRNA expression studies showed a significant and marked decrease in RANKL gene expression on the square-textured surface; by contrast, the ratio of OPG/RANKL showed a significant increase. These results indicate that Co-Cr-Mo surface textures affect osteoblast proliferation, morphology and gene expression; the microenvironment of implant should be considered in the future design. [ABSTRACT FROM AUTHOR]

Abstract: Surface treatments using bio-technology are valuable and fascinating in the sense that such treatments are natural and yield good biocompatibility. Calcium oxalate whiskers for biomedical applications were successfully synthesized on the CoCrMo alloy surfaces implanted in Aloe leaves which consist of many active bio-chemical elements. The effect of surface wettability and surface morphology on the formation of whiskers was investigated using four differently treated CoCrMo surfaces: (i) smoothly polished surface, (ii) electrochemical etched surface, (ii) textured surface with dimples, and (iv) parallel orientated-grooved surface. Results showed that the formed whiskers had a length ranging between 100μm and 600μm, and a diameter in the range of 2μm to 5μm. Electrochemically etched surfaces had better wettability and were favorably for growing whiskers. Surface morphology with (i) dimple textures or (ii) parallel grooves facilitated the effective control of the size and amount of the grown whiskers. [Copyright &y& Elsevier]

Marine equipment and ships operating in complex environments face high drag consumption and severe surface fouling. Non-smooth biomimetic surfaces with specific microstructures work to reduce surface drag and inhibit fouling. In this work, the biological sharkskin shield scale structure was simplified by the idea of segmented independence to construct a bionic non-smooth surface. Single-crystal lithography was used to create a negative template of the silicon substrate. We created a non-smooth bionic structure on the flexible polydimethylsiloxane (PDMS) surface through die casting and molding. Additionally, the bionic non-smooth surface was modified by decorating zeolitic imidazolate framework-67 (ZIF-67) particles to modulate the antifouling properties. Based on tests performed on a self-designed and processed circulating water bath laboratory bench (CWBLB), results showed the non-smooth surface effectively reduced drag by 7.3% compared to that of smooth surface. The contact angle (CA) measurement and anti-bio-adhesion experiment on the surface showed that PDMS surface CAs increased from 109.78° to 140.71°, and Chlorella vulgaris attachment was decreased by 65.3%. The non-smooth bionic surface effectively reduces drag and antifouling, and the effectiveness of the antifouling can be significantly enhanced by augmenting and regulating the particle surface modification method. Our results provide a feasible solution for ship drag reduction and antifouling, which is critical for industrial applications and sustainable development. • A method for processing single-crystal lithography of non-smooth hydrophobic surfaces has been developed. • A circulating water bath laboratory bench was designed, which can be used to measure axial resistance. • The ZIF-67 particle-modified surface possesses excellent resistance reduction and anti-fouling effects. [ABSTRACT FROM AUTHOR]

Abstract: Surface wettability behaviors of three kinds of laser textured Co–Cr–Mo alloy surfaces (arrays of circular, triangular and square shape dimples) were evaluated in aqueous bovine serum albumin (BSA) solution. The tribological properties of laser textured Co–Cr–Mo alloy were investigated by pin–on–disc reciprocating tribometer under BSA lubrication. The wetting surfaces ranging from superhydrophilic (CA=21.5°) to superhydrophobic (CA=142.2°) were obtained by dual/combined surface modification including laser surface texturing (LST) and further fluoro-alkyl silane (FAS). It was found that surface wettability behaviors of Co–Cr–Mo alloy surfaces were closely related to their tribological behaviors in BSA solution. Results showed that the contact angle of circular dimple was the most stable, sliding time of the friction pair reaching steady state stage was shortest and coefficient of friction was minimum among three regular layout shapes of dimples during the tribological tests. It suggests that the combined surface modification of LST and FAS is a promising method to improve the tribological performances and prolong the service life of Co–Cr–Mo orthopedic implants. [Copyright &y& Elsevier]

Ultraviolet (UV) sensors offer significant advantages in human health protection and environmental pollution monitoring. Amongst various materials for UV sensors, the zinc oxide (ZnO) nanostructure is considered as one of the most promising candidates due to its incredible electrical, optical, biomedical, energetic and preparing properties. Compared to other fabricating techniques, hydrothermal synthesis has been proven to show special advantages such as economic cost, low-temperature process and excellent and high-yield production. Here, we summarize the latest progress in research about the hydrothermal synthesis of ZnO nanostructures for UV sensing. We particularly focus on the selective hydrothermal processes and reveal the effect of key factors/parameters on ZnO architectures, such as the laser power source, temperature, growth time, precursor, seeding solution and bases. Furthermore, ZnO hydrothermal nanostructures for UV applications as well as their mechanisms are also summarized. This review will therefore enlighten future ideas of low-temperature and low-cost ZnO-based UV sensors. [ABSTRACT FROM AUTHOR]

Heavy metals have caused widespread concern due to their adverse effects on aquatic organisms. However, there are few studies on their tolerance mechanism. In this study, the tolerance mechanisms of Cyclotella sp. to Cr(VI) were explored. The increase of antioxidant enzymes activity acting as a defense mechanism could help Cyclotella sp. to reduce the oxidative damage caused by the heavy metal Cr(VI). Cr(VI) was also combined with the functional groups on the cell surface to detoxify and was transported into the cell by binding to the carrier protein. In addition, it is worth noting that the molecular docking simulation showed that Cr(VI) combined with macromolecular compounds in cells through hydrogen and ionic bonds, which can reduce the toxicity of chromium. The determination of chromium content in cells showed that chromium was accumulated in cells. Furthermore, the low concentration of Cr(VI) had a growth stimulation on Cyclotella sp., while the growth of Cyclotella sp. microalgae was obvious inhibited when Cr(VI) concentration was over 0.5 mg/L. The content of Chlorophyll a (Chl-a) and soluble protein both had a dramatic change under the stress of Cr(VI). Cell ultrastructure analysis showed that plasmolysis phenomenon and dissolution of organelle structures when Cyclotella sp. was exposed to Cr(VI). The series of changes in Cyclotella sp. allow it to be an indicator of Cr(VI) pollution in water. Meanwhile, these findings were helpful to further understand the tolerance mechanism of Cr(VI) on microalgae and provide new insights to assess Cr(VI) toxicity to the microalgae. • Cr(VI) bounded with the functional groups on the cell surface to detoxify. • Cr(VI) was transported into the cell after binding with the membrane proteins. • Cr(VI) was accumulated in cells of Cyclotella sp. to detoxify. • Molecular docking simulation confirmed that Cr(VI) bounded with proteins through hydrogen and ion bonds. [ABSTRACT FROM AUTHOR]

3D printing has shown promise in the development of notable sensing and health detection devices. Nonetheless, challenges remain in the concurrent development of highly durable wearable sensors with low‐friction surfaces. This challenge serves as a limiting factor in the operational lifespans of these sensors. In this study, a magnetically assisted 3D printing technique is developed to fabricate composites reinforced with magnetic Fe3O4@SiO2 nanochains (NCs) with dimensions of 60.2 µm in length (L) and 0.2 µm in diameter (D), indicating an L:D ratio exceeding 300. By applying a vertical magnetic field and extrusion flow field to the sensor's surface layer, the NCs can be arranged differently (together with the printed textures), reducing the coefficient of friction by 27.7% and improving the wear resistance. This approach is inspired by nacre, known for its impressive durability and resilience. A motion monitoring sensor with an extended lifespan is successfully fabricated by using liquid metal ink integrated with an anti‐wear layer. These findings offer significant insights into the evolution of wearable sensors, demonstrating their adaptability to multi‐material printing and resulting in improved performance and service lives. [ABSTRACT FROM AUTHOR]

Hyaluronic acid (HA) as a major constituent of bionic synovial fluid (BSF) has significant role in lubrication of human body hip joint. Those who mostly suffer from joint related disease prefer to try injections of synovia over of total hip replacement (THR). However, affection of the metabolism process to the injected synovia is able to decrease the life time of the prostheses. In this study, injectable and thermosensitive agarose hydrogel as a carrier for hyaluronic acid has been investigated to extend the life time of the artificial hip joints. Experimental evidences reveal bioactivity, superior viscoelasticity and naturally amorphous network structure of the HA. This material in combination with the large molecules of agarose is able to create three-dimensional polymeric network for separating the conterminous surfaces of bearings and improve the lubrication with more than 30 % reduction rate for coefficient of the friction. Role of mechanical and rheological properties of designed polymeric network in cumulative sustained released of lubricants has been widely investigated. Novelty of the present work provides a survey to the long-term lubrication of artificial hip joints. • Agarose hydrogel has been designed as an efficient carrier for hyaluronic acid. • Hydrogel released lubricant will improve the lubrication of artificial hip joints. • Hydrogel mechanical and rheological behavior is discovered to be a function of pore distribution. • Released solution of the agarose-hyaluronan hydrogel was able to reduce the average of frictional coefficient and protect the surface of the ceramic. [ABSTRACT FROM AUTHOR]

Due to their bioinert and reliable tribological performance, cobalt chromium molybdenum (CoCrMo) alloys have been widely used for articular joint implant applications. However, friction and wear issues are still the main reasons for the failure of implants. As a result, the improvement of the tribological properties and biocompatibility of these alloys is still needed. Thus, surface modification is of great interest for implant manufacturers and for clinical applications. In this study, a strategy combining laser surface texturing and chitosan grafting (mussel inspired) was used to improve the tribological and biocompatible behaviors of CoCrMo. The microstructure and chemical composition were investigated by atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. The tribological properties were discussed to determine their synergistic effects. To evaluate their biocompatibility, osteoblast cells were cocultured with the modified surface. The results show that there is a distinct synergistic effect between laser surface texturing and polymer brushes for improving tribological behaviors and biocompatibility. The prepared chitosan brushes on a textured surface are a strong mechanism for reducing friction force. The dimples took part in the hydrodynamic lubrication and acted as the container for replenishing the consumed lubricants. These brushes also promote the formation of a local lubricating film. The wear resistance of the chitosan brushes was immensely improved. Further, the worn process was observed, and the mechanism of destruction was demonstrated. Co-culturing with osteoblast cells showed that the texture and grafting have potential applications in enhancing the differentiation and orientation of osteoblast cells. [ABSTRACT FROM AUTHOR]

MXene, a two-dimensional (2D) material consisting of Ti 3 C 2 T x , has demonstrated significant potential for numerous applications, particularly in the areas of corrosion and wear resistance to protect metals. In this study, we reported the facile preparation of MXene/epoxy resin (EP) coatings through blending, which was successfully confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). With the lubrication of oleic acid (OA), an EP coating containing 1 wt% MXene exhibited superlubricity with a remarkably low coefficient of friction (COF) of 0.008. Furthermore, compared to the pristine substrate, the coating achieved an impressive reduction in the wear rate of 99.73 %. Under simulated seawater conditions, the coating demonstrated an exceptional corrosion protection efficiency (PE) of 99.38 %, which was attributed to the corrosion inhibition effect of MXene. The observed superlow friction was primarily attributed to the synergistic effects of a tribo-film of OA, the presence of the MXene film, and the improved mechanical properties of the EP coating due to the incorporation of MXene. Our study highlighted the potential of MXene as a protective material in long-term marine applications. • Coatings with both wear resistance and corrosion resistance were prepared. • The prepared coatings could enter the superlubricity regime. • MXene in E51 coating effectively improved the corrosion resistance. • Investigated the potential of MXene as a protective material for long-term marine applications. [ABSTRACT FROM AUTHOR]

In the study, the hydrogen‐free diamond‐like carbon (DLC) coating was deposited on the surface of the Co‐Cr‐Mo alloy. Pin‐on‐plate tribotests were performed for the DLC‐coated CoCrMo specimen against un‐doped CoCrMo alloy under bovine serum albumin (BSA), NaCl solution, and distilled water. Results showed that the average coefficient of friction (COF) of the mating system was 0.08 under NaCl and 0.07 under distilled water, respectively. However, the dynamic COF under BSA lubrication was prone to increasing with testing time, and the average COF got to 0.12. The wear morphology of the pin was covered by the carbon transfer layer without BSA lubrication, and the formation of the transfer layer was a dynamic evolution process as wear debris adhesion, continuous transferring, and delamination. Oppositely, the transfer layer was inhibited under BSA lubrication due to the adsorption of the protein layer on the contact interface. [ABSTRACT FROM AUTHOR]

Molecular helical is ubiquitous in molecular structures, however, the impact of the structure on mechanical properties has yet to be extensively studied. In this study, we synthesized a single network κ-carrageenan (KC) hydrogel with the molecular double helix structure, and elucidated its unique self-enhancing and damping properties from a molecular structural perspective. During cycle tensile tests, the helical structure was stretched and entangled to form a directional arrangement, increasing the elastic modulus and achieving 'self-reinforcement'. Meanwhile, the molecular helices have a spring-like damping effect, allowing the hydrogel to dampen low-frequency noise while transmitting high-frequency signals. By utilizing the hydrogel to create electrodes for electrocardiogram (ECG) detection, we were able to effectively filter out noise generated by movements while retaining necessary signals. Our work thus presents a potential pathway bridging from microscopic molecular structure to macroscopic mechanical properties of materials. [ABSTRACT FROM AUTHOR]

The biomimetic sharkskin riblet has attracted more attention in engineering and research owing to the economic benefit of drag-reducing and antifouling properties. Although several works have optimized the parameters for a number of riblet designs, there is not yet a study dedicated to optimizing for rectangular cuboidal riblet parameters. Hence, this work proposes a new numerical optimization of riblet orientations and arrangements of a three-dimensional rectangular cuboidal riblet. The shear-stress transport k-omega was adopted as an appropriate turbulence model for the simulation. The results showed that the riblets efficiently improved drag reduction regardless of the flow state. Riblets oriented perpendicularly to the flow direction showed the greatest performance of 11.3% and 6% in the laminar and turbulent flow, respectively. Moreover, the analysis of the flow field characteristics near the wall revealed a significant improvement in terms of reduction in near-wall velocity and shear stress. This work offers new perspectives on the role of the intricate multifunctional architecture of shark-scale structures in improving swimming speed and opening new doors for marine and underwater applications. • A numerical study of 3D shark riblets with different orientation and arrangement. • The SST k − ω model was adapted and laminar and turbulent conditions were discussed. • Simplified riblets greatly improved drag reduction regardless of the flow state. • Maximum performance was 11.3% and 6% in laminar and turbulent flow, respectively. • A significant reduction in near-wall velocity and shear stress was revealed. [ABSTRACT FROM AUTHOR]

The maintenance cost of a heavy truck increases due to the severe damage of thrust washer in the differential. The wear was usually related to the contact stress concentration. In the study, the finite element analysis (FEA) was performed for identifying the source of the abnormal wear of thrust washer. An improved approach of modifying the surface profile of spider gear back was proposed. FEA simulations were further conducted to investigate the effect of different spider gear back parameters on the tribological behavior of thrust washer. The FEA simulation results were verified by tribological experiments. Results showed that: (i) the abnormal wear of thrust washer pairing the original gear was caused by the local stress concentration; (ii) the local stress concentration could be eliminated by modifying the surface profile of spider gear back; (iii) using the modified spider gear back, the wear mass loss of the thrust washer was reduced significantly; (iv) the promising surface radius of spider gear back was 73.15 mm. [ABSTRACT FROM AUTHOR]

• Introduces a reversible electroadhesion method using low ion migration. • The mechanism of reversible adhesion was explained by electrochemical means. • Describes electrochemical stability, maintaining charge capability after 1000 cycles. Reversible adhesions have exhibited a great potential in the biomedical field. Here, we designed a reversible electroadhesion between anionic κ-carrageeenan hydrogel and physiological saline-based nonionic polyacrylamide hydrogel through the low and controllable ion migration. A robust adhesion was obtained between the hydrogel pairs via a direct current (DC) of 10 V. Upon the application of a reverse voltage, the pair could be effortlessly and rapidly detached. We elucidated the mechanism of reversible electroadhesion through electrochemical analysis, attributing the adhesion to the formation of double ion layers between the adhesive interfaces under the electrical field and pH variation. When a reverse voltage was applied, the adhesion strength was dropped lower than 0.1 kPa and the detachment was occurred due to the disruption of the double ion layer by ionic migration and even diffusion. Moreover, the adhesion system demonstrated outstanding electrochemical stability, with less than a 7 % variation in charge storage capability after 1000 cycles. The proposed strategy paves the way for developing high-performance adhesion hydrogels with electrically controllable functions, which are indispensable for various emerging fields like tissue repair and soft biomedical applications. [ABSTRACT FROM AUTHOR]

Nanoparticles are extensively utilized as effective lubrication additives. In a novel approach, one-dimensional nanoparticles undergo self-assembly, transforming into two-dimensional nanochains for use as additives, thereby enabling varied lubrication effects. We involved synthesizing Fe 3 O 4 nanoparticles via a solvothermal method, followed by their self-assembly into magnetic Fe 3 O 4 @SiO 2 nanochains under a magnetic field. These NCs, measuring 57.8 µm in length and 0.2 µm in diameter, were dispersed in deionized water. This study explored the influence of various orientations on the tribological properties of the lubricant through the manipulation of nanochains' alignment using a magnetic field. The results indicate a 48.51% reduction in coefficient of friction and a 73.56% decrease in wear rate when the NCs were aligned perpendicular to the direction of friction. [Display omitted] • Self-assembly forms Fe 3 O 4 @SiO 2 nanochains with good interfacial bonding. • The vertically aligned nanochains greatly reduce the coefficient of friction. • The vertically aligned nanochains act as rolling bearings. • The main forms of wear include adhesive, abrasive, and three-body abrasion. [ABSTRACT FROM AUTHOR]

• Antioxidant enzyme activities were increased to resist peroxidative damage. • Intracellular Cr(VI) was converted to Cr(III) in order to improve tolerance. • Cr(VI) bounded with intracellular proteins by hydrogen bonds to detoxify. The effects of the initial concentrations of Cr(VI) on chlorophyll- a (Chl- a), soluble protein and ultrastructure were investigated. Results showed that <0.5 and >1.0 mg L−1 Cr(VI) stimulated and inhibited the growth of Isochrysis galbana , respectively. The tolerance mechanisms of I. galbana to Cr(VI) included the following: (1) increased activities of superoxide dismutase (SOD) and peroxidase (POX) for peroxidative damage resistance, (2) accumulation of Cr(VI) on the cell surface and inside the cell for detoxification and (3) conversion of intracellular Cr(VI) to less toxic Cr(III) as indicated by X-ray photoelectron spectroscopy (XPS) results. Cr(VI) enrichment by I. galbana may cause damage to marine ecology and human bodies through the food chain. The tolerance mechanisms of I. galbana to Cr(VI) may be potentially used to treat low-concentration Cr(VI) wastewater. Therefore, the responses and tolerance mechanisms of I. galbana to Cr(VI) must be further studied. [ABSTRACT FROM AUTHOR]

MoSe 2 nanoparticles were successfully synthesized by hydrothermal method and treated with a novel dispersion method, ultrasonic dispersion in water. The tribological behaviors and wear mechanisms of MoSe 2 nanoparticles as oil additives were investigated using a reciprocating ball-on-disk tribo-meter. The results showed that the average friction coefficient and wear rate decreased by 43% and 87% respectively with the addition of the treated MoSe 2 nanoparticles compared with white oil. The lubrication mechanism was investigated and can be interpreted as that the MoSe 2 had smaller particle size after being ultrasonically dispersed in water, which were beneficial to the formation of the tribo-film. 1. This study proposed a method to treat MoSe 2 nanoparticles that were synthesized by hydrothermal method. 2. The lubrication effects of white oil were greatly enhanced with the addition of MoSe 2 nanoparticles. 3. The tribological mechanism was discussed. [ABSTRACT FROM AUTHOR]

An effective method of edge deburring in laser surface texturing was presented. Tribologically, suitably orientated micro-dimples on Co-Cr-Mo alloy can effectively reduce interfacial friction due to their storing of wear debris. However, burrs generated around dimple rim during laser irradiation inclined to cause plowing wear due to their piercing and cutting effect. This study was conducted to evaluate a technique for improving the quality of the laser-irradiated textures by implementing a freezing water layer to cover onto the texturing substrate surface. The existence of such freezing water layer reduced both Young's modulus and hardness of the substrate material around the peripheral edge of the laser-ablated textures. Experimental results showed that integrating the laser texturing technology with the freezing water layer effectively constrained the deburring, and its beneficial mechanism in improving the quality of textures was also propounded. The irradiation technique reduced simultaneously the friction coefficient and wear. [ABSTRACT FROM AUTHOR]

Excessive wear debris in prosthesis tends to induce loosening, which is a major problem affecting the durability of long-serving implants. Although bionic synovial fluid can be used to improve the lubrication of artificial joints, the fluid is often absorbed easily by the tissues of human body. To enhance the effectiveness of bionic synovial fluid, poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCEC) hydrogel was prepared as a carrier for the bovine serum albumin (BSA) in synovial fluid. It thus significantly reduces the loss rate of BSA. Experimental results show that the good sustainability and favorable release ability of hydrogel efficiently prevent the rapid outflowing of BSA. Experiments also reveal that the PCEC hydrogel inclines to form a particular structure with BSA and thus give BSA an excellent slow-release performance. Furthermore, friction and wear tests indicate that the released solution from the PCEC hydrogel possesses good lubricating properties. In general, the average friction coefficient of released solution is approximatively 77% lower than that of the normal phosphate-buffered solution. This study furnishes with an effective approach to prolong the lubricating duration of BSA in artificial prostheses. [ABSTRACT FROM AUTHOR]

Microalgae, the primary producers in water ecosystems, are the main food of fish and shrimp. Microalgae have a great capacity to absorb heavy metals, and low concentrations of heavy metals can promote the growth of them. But high concentrations have a strong influence on the physiological and biochemical processes in algae, such as growth, photosynthesis, cell ultrastructure, protein content and fatty acid composition. Heavy metals may also induce the formation of reactive oxygen species (ROS), which causes the oxidation damage of protein, lipid and thiol peptides, and activates the antioxidant system. Heavy metals can be removed or converted into another state by biosorption of cell surface, accumulation in cells, combining with antioxidant enzymes and so on. This review summarized the responses of microalgae to heavy metals and comprehensively described the removal and tolerance mechanisms by extracellular adsorption and intracellular accumulation, which are helpful to treat pollution and improve the culture of microalgae. • Responses of microalgae to heavy metal stress. • Mechanisms of heavy metal tolerance in microalgae. • Accumulation of heavy metals in the microalgae cells. • The technology for researching algae and treating wastewater. [ABSTRACT FROM AUTHOR]

This paper focuses on the fault-tolerant control problem for an Internet-based three-tank system in the presence of possible sensor bias faults. The Internet-based three-tank system is an experimental setup that can be regarded as a typical networked system for evaluating networked fault-diagnosis and fault-tolerant control methods. Packet dropout phenomenon in the sensor-to-controller link is considered in this paper, and the fault type we deal with is chosen as the sensor bias fault. Fault-diagnosis unit is designed toward an auxiliary system. Sensor bias faults can be detected by comparing the residual signal generated by the fault detection filter and a prescribed threshold. After that, the fault can be isolated by using the residual analysis approach. Once the fault is isolated, it can be estimated iteratively in the least-squares sense. A fault accommodation method is proposed, and a fault-tolerant control strategy is achieved based on the fault information provided by the fault-diagnosis unit. The approach brought forward in this paper is demonstrated via an experimental study on the practical Internet-based three-tank system. Results show the effectiveness and the applicability of the proposed techniques. [ABSTRACT FROM PUBLISHER]

The riblet structure on the surface of the shark skin provides significant drag reduction and fouling protection. Inspired by the structure of the shark skin, we present a direct ink writing protocol by modifying the rheological properties of polydimethylsiloxane to make it printable, and a series of flexible surfaces have been created with drag reduction and antifouling. The shear stress transport k–omega model was used as a suitable turbulence model for the numerical study to compare with results of drag reduction tests. Simulations and tests proved that printed non-smooth surfaces effectively reduced water drag, where the maximum drag reduction rate reached 18.16 % at 0.06 m/s. Through the analysis of the characteristics of the flow field near the wall, the drag reduction mechanism of the riblet surface was examined. Moreover, the antifouling tests revealed that the printed surface exhibited excellent fouling resistance and inhibited the spread of dirt on the surface. Our findings may provide a new surface skinning strategy for ships, underwater vehicles and wearable devices to reduce drag and contaminant adhesion and improve navigation efficiency and longevity. [Display omitted] • A convenient method for preparing commercial silicone rubber (PDMS) that can be used for direct ink writing is presented. • Preparation of large flexible skins with integrated drag reduction and antifouling design. • The maximum drag reduction for printed non-smooth surfaces is 18.17 %. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS), as a polymer material with excellent mechanical properties and flexibility, is widely used in flexible wearable devices, soft robots and other fields. Commonly, the Mold-flipping is used to produce PDMS based samples, while it is time-consuming and impractical for the large-scale fabrication. With the additive manufacturing, printing pastes can be freely configured thanks to direct ink writing (DIW) technology, enabling rapid and high precision manufacturing. Herein, we have improved the rheology of Sylgard-184 by adding crosslinkers and silica nanoparticles to make it printable. By adjusting the printing path, flexible surfaces with textures were created. Ball-on-disc dry friction experiments were carried out on the specimens. Results show that the texture produced by the print path can effectively reduce the coefficient of friction (COF) compared to samples produced by the conventional molding. When the print path is at 60° to the sliding direction, COFs for samples are reduced by 23.2% to 32.9%. Our findings provide a new strategy for preparing flexible and wearable devices through significantly enhancing the wear resistance of substantiable usage and prolonging the lifespan. • A method for preparing Polydimethylsiloxane (PDMS) that can be used for direct ink writing has been proposed. • Flexible surfaces prepared at different printing angles have a reduced coefficient of friction compared to cast surfaces. • The coefficient of friction can be reduced by up to 32.9% when printing at an angle of 60°. [ABSTRACT FROM AUTHOR]

Abstract: Six chemical sulfated polysaccharide derivatives (PFP-S) with variable degree of substitution (DS) and molecular weights (Mw) were prepared from the fresh persimmon fruits by chlorosulfonic acid-pyridine and ultrasonic degradation methods, and the effectiveness of the reaction was monitored by the DS, FT-IR and ζ-potential analysis. The sulfation modification might cause advanced structure change to the samples, the SEM of PFP-S exhibited a polyphasic convoluted structure. Results of anticoagulant activities showed that PFP-S could prolong activated partial thromboplastin time (APTT) and thrombin time (TT), but not prothrombin time (PT), and the anticoagulant activity improved with the increasing DS and decreasing Mw. [ABSTRACT FROM AUTHOR]

Abstract: In this study, three kinds of chemically sulfated polysaccharides (PFP-S) were derived from a water-soluble polysaccharide of persimmon fruit with chlorosulfonic acid–pyridine method. Relationship between the degree of substitution and immunomodulatory activity of PFP-S was examined with the splenocytes experiment. The results showed that the splenocytes-activating activity was significantly enhanced by PFP-S in all the groups compared with control group (P <0.01). PFP-SII exhibited the most potent splenocytes-activating activity by increased cytokine production and NO release. It also suggested that the sulfate groups and molecular weight of polysaccharides are key factors to regulate the immunomodulatory activities. [Copyright &y& Elsevier]

In this paper, we study the crystal structures, density of states, electronic band structures and thermoelectric transport properties of SrCuChF (Ch = S, Se and Te) by the way of the first principle. The pictures of electronic band structure show the relatively large dispersion near the maximum value of valence band in the directions of Γ-M and Γ-X, but in the direction of Γ-Z, the band structure is relatively flat, and the top of valence band is mainly composed of Cu-Ch anti-bond state which has a very significant impact on the transport performance of p-type SrCuChF. Base on the semiclassical Boltzmann transport theory, we find that the p-type SrCuChF has a high value of Seebeck coefficient due to the quasi-flat character of the electronic bands at the edges of the valence band, and the outstanding anisotropic properties due to their natural layered structure. According to the predicted maximum value of power factors, the optimal doping concentration is presented. Therefore, we give a natural layered structure complex SrCuChF with the good thermoelectric properties and may find many important applications in the thermoelectric functional materials. [ABSTRACT FROM AUTHOR]