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One of the most important features expected from protective coatings is good adhesion to the substrate. In this paper, TiNi/MoS2 functional solid lubricant coatings were deposited by closed field unbalanced magnetron sputtering system on 52100 and D2 steels. The adhesion and multipass scratch characterization of the coatings were investigated. The obtained results were analyzed in terms of deposition parameters, as well as structural and mechanical properties of the coatings. Adhesion properties of the coatings were determined by scratch tests with a progressive load. The fatigue-like behaviors of the coatings were obtained by the bidirectional multipass scratch test with a constant load. The results showed that the TiNi/MoS2 has high adhesion and multipass scratch resistance than the literature results. The coatings deposited on the 52100 steel yielded better performance.

Finger-like radial hierarchical micropillars with folded tips are observed on the surface of the rose pistil stigma (RPS). Impressively, a water droplet on the surface of the RPS presents a spherical shape and it still hangs on the surface even when the RPS is turned over. Superhydrophobicity and high adhesion to water are demonstrated on the RPS, which is beneficial for the RPS to remain clean and fresh. The special wetting behavior of the RPS is highly related to its hierarchical microstructures and surface chemistry. Finger-like hierarchical micropillars with a high aspect ratio are capable of retaining air to support superhydrophobicity while the microgap between the micropillars and on the hydrophilic tips enables the RPS to retain a high adhesion to water. These findings about the unique wetting behaviors of the RPS may provide inspiration for the design and fabrication of functional wetting surfaces for diverse applications such as microdroplet manipulation, three-dimensional cell culture, and microfluidics.

Hierarchical Cu2O/CuO/TiO2 hollow nanostructured films with petal effect (high superhydrophobicity and high adhesion to water droplets) have been synthesized through a facile solvothermal approach,...

This study presents wet-responsive, shape-reconfigurable, and flexible hydrogel adhesives that exhibit strong adhesion under wet environments based on reversible interlocking between reconfigurable microhook arrays. The experimental investigation on the swelling behavior and structural characterization of the hydrogel microstructures reveal that the microhook arrays undergo anisotropic swelling and shape transformation upon contact with water. The adhesion between the interlocked microhook arrays is greatly enhanced under wet conditions because of the hydration-triggered shape reconfiguration of the hydrogel microstructures. Furthermore, wet adhesion monotonically increases with water-exposure time. A maximum adhesion force of 79.9 N cm–2 in the shear direction is obtained with the hydrogel microhook array after 20 h of swelling, which is 732.3% greater than that under dry conditions (i.e., 9.6 N cm–2). A simple theoretical model is developed to describe the measured adhesion forces. The results are in go...

The transport of small quantities of liquid on a solid surface is inhibited by the resistance to motion caused by the contact between the liquid and the solid. To overcome such resistance, motion can be externally driven through gradients in electric fields, but these all inconveniently involve the input of external energy. Alternatively, gradients in physical shape and wettability - the conical shape of cactus spines to create self-propelled motion. However, such self-propelled motion to date has limited success in overcoming the inherent resistance to motion of the liquid contact with the solid. Here we propose a simple solution in the form of shaped-liquid surface, where solid topographic structures at one length scale provides the base for a smaller length-scale liquid conformal layer. This dual-length scale render possible slippery surfaces with superhydrophobic properties. Combined to an heterogeneous topography, it provides a gradient in liquid-on-liquid wettability with minimal resistance to motion and long range directional self-propelled droplet transport. Moreover, the liquid-liquid contact enables impacting droplets to be captured and transported, even when the substrate is inverted. These design principles are highly beneficial for droplet transport in microfluidics, self-cleaning surfaces, fog harvesting and in heat transfer., 11 pages, 4 figures

Damage to the responsive superwetting material by external stimuli during the responsive process has been a ticklish question in recent years. We overcome this barrier by imitating a peanut leaf and designing a humidity-responsive MIL-100 (Fe)/octadecylamine-coated stainless steel mesh (HR-MOS). Such a material shows superhydrophilicity when ambient humidity is higher than saturated humidity, while it shows superhydrophobicity and high adhesion to water when ambient humidity is lower than saturated humidity. The peanut leaf-like two-level nanostructure of MIL-100 (Fe) is speculated as the principal factor to bring about the binary synergy wettability of the material. Accordingly, the material can realize humidity-controlled separation of at least 12 types of emulsions along with satisfactory durability. The responsive condition of the material is mild and green, which does lower damage to the material and environment. This strategy is the first to realize humidity-responsive wettability transition and provides a novel approach for manually controlled environmental protection.

Various bio-inspired dry adhesive materials have been investigated. In this work, lithography and silicon deep etching method were used to fabricate bio-inspired micro-pillar dry adhesive materials of which the parameters, such as side length, Height to Side length Aspect Ratio (HSAR), and inter-pillar Distance to Side length Aspect Ratio (DSAR) were comprehensively studied to obtain a dry adhesive with high adhesion. An orthogonal array method was designed and a series of fabrication experiments were conducted to identify optimum parameters, which resulted in a high normal adhesion of 2.98 N·cm‒2 and a shear adhesion of 9.59 N·cm‒2. An adhesion and desorption device was further designed on basis of the optimum dry adhesive, which enables an Unmanned Aerial Vehicle (UAV) to successfully adhere on and detach from a ceiling. This would allow an UAV to stay aloft for prolonged time, which could be invaluable to many applications, such as energy conservation and aerial detection.

Tremendous attention has been focused on the design and fabrication of intrinsic self-healing materials in recent years; however, the fabrication of self-healing materials with high transparency and high adhesion strength is still a challenge. Here, we develop a novel transparent self-healing adhesive with multiple functions by simply blending poly(2-ethyl-2-oxazoline) (PEOZ), poly(4-hydroxy styrene) (PHS), and CaCl2, and discover that the anion Cl− also plays a significant role in accelerating the self-healing process by anion–ligand coordination in the form of hydrogen bonding, which has been seriously neglected in previous work. Unlike the common single metal–ligand coordination approach, the enhancement of self-healing results from novel co-existing ternary bridging bonds: metal–ligand coordination, ionic bond, and anion coordination. The universality of the new concept has been verified with other typical soluble salts MgCl2, NaCl, and Ca(NO3)2, providing a new dimension in the comprehension of the self-healing mechanisms. As a result, the hybrid shows outstanding multifunctional performance compared with the most recently published self-healable adhesives taking into consideration the transparency (T550 = 98.9%), adhesion strength (2.57 MPa), and self-healing efficiency (91%), enabling its application as an optical material, an adhesive and also a conservation material for cultural heritage.

Surface materials with the capability of manipulating droplet play important roles in a wide range of fields from science to industry. In this work, a velocity-controlled laser surface texturing strategy was developed to fabricate micro/nano-hierarchical structures on stainless steel surface. Gradient scanning velocity method was initially used to fabricate two samples. Three typical textured zones comprising of different micro/nano-hierarchical structures were created, leading to three different wetting behaviors, i.e., superhydrophobic with low adhesion, near superhydrophobic with high adhesion and wetting with high adhesion. Subsequently, more programmable samples were created with different velocity combinations to investigate the droplet manipulation. Droplet manipulation including fast rolling, capture at designed position and direction guide sliding were successfully achieved. The velocity-controlled laser surface texturing strategy is capable of manipulating droplet on a programmable surface, which makes the strategy excellent candidate for practical applications.

Recently, stimuli-responsive sensors and actuators have drawn significant attention as they are promising in a wide scope of applications, including wearable devices and soft robotics. However, the...

The etherification of ortho-phosphoric acid with triethanolamine and polyoxypropylene glycol is studied. The reaction process is accompanied by the formation of hyperbranched amino ethers of ortho-phosphoric acid terminated by hydroxyl groups. A specific feature of the chemical structure of the compounds obtained is the existence of ion pairs in their structure separated in space. The reaction of the etherification of ortho-phosphoric acid with glycols becomes possible through the use of tertiary amines. The amino ethers of ortho-phosphoric acid are investigated as a polyol component for the synthesis of polyurethanes with high adhesion characteristics and strength properties. The experimental results presented allow us to relate polyurethanes obtained on the basis of ortho-phosphoric acid amino ethers to polymers of ionomeric nature.

Bioadhesives have reached significant milestones over the past two decades. Research has shown not only to produce adhesives capable of adhering to dry tissue but recently wet tissue as well. However, most bioadhesives developed have exhibited high adhesion strength yet lack other properties required for versatility in application, such as elasticity, biocompatibility and biodegradability. Adapting from limitations met from early bioadhesives and meeting the current demand allows novel bioadhesives to reach new milestones for the future. In this review, we overview the progression and variations of bioadhesives, current trends, characterisation techniques and conclude with future perspectives for bioadhesives for tissue engineering applications.

Attaching hydrogels to soft internal tissues is crucial for the development of various biomedical devices. Tough sticky hydrogel patches present high adhesion, yet with lack of injectability and the need for treatment of contacting surface. On the contrary, injectable and photo-curable hydrogels are highly attractive owing to their ease of use, flexibility of filling any shape, and their minimally invasive character, compared to their conventional preformed counterparts. Despite recent advances in material developments, a hydrogel that exhibits both proper injectability and sufficient intrinsic adhesion is yet to be demonstrated. Herein, a paradigm shift is proposed toward the design of intrinsically adhesive networks for injectable and photo-curable hydrogels. The bioinspired design strategy not only provides strong adhesive contact, but also results in a wide window of physicochemical properties. The adhesive networks are based on a family of polymeric backbones where chains are modified to be intrinsically adhesive to host tissue and simultaneously form a hydrogel network via a hybrid cross-linking mechanism. With this strategy, adhesion is achieved through a controlled synergy between the interfacial chemistry and bulk mechanical properties. The functionalities of the bioadhesives are demonstrated for various applications, such as tissue adhesives, surgical sealants, or injectable scaffolds.

The relatively high toughness, high adhesion to steel, and low internal stress of hydrogenated amorphous carbon (a-C:H) films containing Ag make them good candidate materials for various applications in sensors, tribology, and biomaterials; however, the relatively low hardness and poor tribological properties in oxidizing environments hinder their broad use. Incorporating a small amount of Si in Ag/a-C:H films may modify the film microstructure and, in turn, improve their mechanical and tribological properties. To test this hypothesis, Ag/Si/a-C:H films were synthesized by magnetron sputtering and their microstructure, composition, and mechanical/tribological properties were examined with various microanalysis techniques and mechanical testing methods. The Si content of the films was varied by controlling the rotational speed of the substrate. It is shown that the incorporation of Si in the films increases the sp 3 C, sp 3 CH, and sp 3 CH2 contents, slightly roughens the film surface, and greatly improves the mechanical and tribological properties through the formation of a SiC phase. The results of this study also show that there is a critical Si content for optimal tribological properties.

Erect Au nanocones with high adhesion to substrates are obtained by simply drawing from Au nano-films through Au-Si eutectic welding. Nanocones with diameters ranging from about 5 to 150 nm and length ranging from about 60 to 600 nm can be observed on both Au and Si substrate surfaces. Nano-scale Au-Si eutectics formed at the rough Au–silicon film interface under annealing at 450 °C and the subsequent cooling process facilitate the formation of nano-bonding points and draw Au nanocones from Au nano-film by mechanical separation. Erect Au nanocones adhered to Au or Si substrates shows higher light enhancement than itself, observed by FDTD simulation. This method provides new strategy for the fabrication of SERS detectors, solar cells et al. with high stability.

With the combination of the passive adhesion generated by micro/nano-structures at their feet and the active mechanical stimulus of their toe muscles, geckos can stably walk on vertical walls and horizontal ceilings. Inspired by such stimuli-responsive systems in nature, an active adhesive soft gripper stimulated by low voltage (usually ≤6 V), consisting of a passive mushroom-like adhesive structure and an electrically active liquid crystal elastomer working as toe muscles, is proposed in this study. Through voltage on/off switching, reversible deformation can be generated for switchable adhesion, where high adhesion can be achieved under the action of a preload force accompanied by a 0 V voltage and low adhesion can be obtained under an exerted voltage. This gecko-inspired soft gripper was tested and found to be successful as a transport device for gripping/releasing objects with different features, such as a glass ball, a sample bottle, and a steel weight. To the best of our knowledge, the present study is the first to propose an electrically active gecko-inspired soft gripper for transferring objects with different surfaces by the control of low voltage, processing great application potential in industrial lines and daily life and providing a novel perspective on soft gripper design.

Over the past few years, shape memory polymer (SMP) has been extensively studied in terms of its remarkable reversible dry adhesive properties and related smart adhesive applications. However, its exceptional properties have not been exploited for further opportunities such as pick-and-place applications, which would otherwise advance the robotic manipulation. This work explores the use of an SMP to design an adhesive gripper that picks and places a target solid object employing the reversible dry adhesion of an SMP. Compared with other single surface contact grippers including vacuum, electromagnetic, electroadhesion, and gecko grippers, the SMP adhesive gripper interacts with not only flat and smooth dry surfaces but also moderately rough and even wet surfaces for pick-and-place with high adhesion strength (> 2 atmospheres). In this work, associated physical mechanisms, SMP adhesive mechanics, and thermal conditions are studied. In particular, the numerical and experimental study elucidates that the optimal compositional and topological SMP design may substantially enhance its adhesion strength and reversibility, which leads to a strong grip force simultaneously with a minimized releasing force. Finally, the versatility and utility of the SMP adhesive gripper are highlighted through diverse pick-and-place demonstrations.

A peak force quantitative nanomechanical mode (PF-QNM) can be used to simultaneously measure the topographical and nanomechanical property maps of samples. Currently, few studies used this mode to investigate the phase characteristics of bitumen in mastics and mixtures. The present study adopted hot-bitumen-pouring methods to prepare base bitumen surface samples and further used frozen-storage and low-temperature-cutting methods to prepare the internal samples of base bitumen in mastics and mixtures. Then, the atomic force microscopy (AFM) PF-QNM mode was used to collect data on the topographical and nanomechanical properties of bitumen and bitumen in mastics and mixtures. The results indicated that a typical bee structure only appeared on the bitumen surface. In contrast to the bitumen surface, the bitumen interior showed two phases, A- and B-phase, which were close in some properties to the periphase and paraphase of the bitumen surface, respectively. Furthermore, the addition of mineral aggregates affected the phase characteristics of the free bitumen interior. With an increase in the mineral aggregate surface area, the proportion of A-phase decreased and that of B-phase increased in the free bitumen interior. LAY DESCRIPTION: Bitumen is a complex mixture of hydrocarbons primarily applied for pavement materials. In the pavement industry, the bituminous mixture is a multilevel system, in which bitumen acts as a binder binding the aggregates and fillers to form bituminous mixture. Currently, atomic force microscopy (AFM), which is an advanced microscopy technology, has been used to investigate bitumen surface phase characteristics at the nanoscale. However, few studies have directly explored the nanoscale phase characteristics of bitumen in mastics or mixtures. Recently, with the progress of technology, a peak-force-quantitative-nanomechanical mode (PF-QNM) can be used to simultaneously measure the topographical and nanomechanical property maps of samples. Relying on this advanced mode, this study analyzed the nanoscale phase characteristics of the bitumen surface and interior, and further explored the effect of mineral aggregates on bitumen interior phase characteristics. In detail, we used hot-bitumen-pouring methods to prepare bitumen surface samples and adopted frozen-storage and low-temperature-cutting methods to prepare the internal samples of bitumen in mastics and mixtures. Subsequently, AFM PF-QNM mode was used to collect topographical and nanomechanical property maps of bitumen and bitumen in mastics and mixtures. The results indicated that the bitumen interior only consisted of two phases, where the A-phase presented low adhesion, deformation, and dissipation, while the B-phase presented high adhesion, deformation, and dissipation. A-phase and B-phase of the bitumen interior were close to the periphase and paraphase of the bitumen surface, respectively. Furthermore, the addition of mineral aggregates significantly affected the bitumen interior phase characteristics.

Recent investigations demonstrated the applicability of diamond-like carbon (DLC)-coated tools for dry forming of aluminum, which is a challenging application field due to the high adhesion tendency of aluminum. An exceptionally low roughness of the coated forming tool is required to prevent adhesion-induced tool failure. To establish dry forming of aluminum in industrial production processes, efficient methods must be developed to manufacture DLC-coated forming tools with reproducible high surface quality. This paper illustrates two DLC coating processes that are especially optimized for deposition of nanoscopically smooth DLC tool coatings. Two optimized coating systems were deposited, characterized, and subsequently evaluated using application-oriented strip drawing tests to validate their performance in comparison with a state-of-the-art coating system. One coating process showed high potential for production of DLC-coated forming tools with the required surface quality.

In this work, a pattern-free and high-throughput droplet platform with low reagent consumption, and applicable for on-site preliminary screening of ions is proposed. The droplet platform is composed of nanowire-nanopillar double-layer forests with features of superhydrophobicity and high adhesion, and it can tightly capture analyte droplets with a large contact angle. The platform is fabricated simply by plasma-treating of polyimide, silicon etching, and decoration of hexamethyldisilazane (HMDS) molecules. Based on such a droplet platform, detection of chromium ions through chromogenic reaction is successfully realized. It is expected that such a platform can be used for on-site ion screening with various concentrations and species.

Carbamide peroxide (CP) possesses a strong tooth bleaching activity, however, its clinical application is limited because of its instability in aqueous formulations. This study explores the improvement of CP stability and bleaching activity by loading CP in electrospun nanofibrous film (ENF). Polyvinylalcohol, polyvinylpyrrolidone, and silica were used as components for core-based nanofibers of ENF. Electrospinning feed aqueous solutions (EFASs) were developed for preparing CP loaded ENF (CP-ENF). Stability of CP in EFASs is significantly higher than in pure water. The highest stability of CP is found in PPS-CP3, composed of 0.5% CP, 5.5% polyvinylalcohol, 3% polyvinylpyrrolidone, and 1% silica. The results from X-ray diffraction indicate that CP is dispersed as a non-crystalline form in CP-ENFs. CP and the compositions of EFASs play a major role on characteristics and bleaching efficiency of CP-ENFs. Drug release of CP-ENFs is the first order kinetics. CP-ENF obtained from PPS-CP3 shows the highest drug entrapment efficiency, high adhesion, and suitable sustained release. Drug release mechanism is along with anomalous transport according to Korsmeyer&ndash, Peppas model. In an ex vivo study using human teeth, it shows the highest bleaching efficiency among the others. Therefore, CP-ENF obtained from PPS-CP3 is a promising ENF for clinical use.

To study the sand erosion damage evolution and mechanism of TiN/Ti multilayer coatings, the coatings with period numbers of 1, 2, 4 and 8, were deposited by combining the techniques of FCVA and MEVVA ion implantation. The coatings were evaluated via nano-indentation and scratcher, and numerical simulations and sand erosion experiments were conducted. All of the coatings show quite high adhesion strengths of ~80 N. Besides, it was found that the deposited defects could lead to premature failure of coating. In the absence of defects, attributing to the maximum tensile stress and highest stress gradient in the exposed topmost TiN layer, the TiN/Ti coatings are generally eroded off as layered. The simulation results showed the high tensile stress distributing on the surface and undersurface of every TiN layer were probably the main factors for crack initiation and brittle flaking. Accordingly, the TiN/Ti coating with one period performed the best erosion resistance, while the coating with eight periods showed the worst performance. These results indicate that based on the high adhesion strength and few defects, the fewer TiN layers in coating, the fewer vulnerable regions with high tensile stress, and resulting in better sand erosion resistance.

In this paper, an efficient and green strategy was developed to synthesize porous magnetic chitosan (PMCS) particles via a special superhydrophobic effect of a porous fluorinated polyimide (PFPI) f...

In this study, a facile and detailed strategy to fabricate superhydrophobic aluminum surfaces with controllable adhesion by femtosecond laser ablation is presented. The influences of key femtosecond laser processing parameters including the scanning speed, laser power and interval on the wetting properties of the laser-ablated surfaces are investigated. It is demonstrated that the adhesion between water and superhydrophobic surface can be effectively tuned from extremely low adhesion to high adhesion by adjusting laser processing parameters. At the same time, the mechanism is discussed for the changes of the wetting behaviors of the laser-ablated surfaces. These superhydrophobic surfaces with tunable adhesion have many potential applications, such as self-cleaning surface, oil–water separation, anti-icing surface and liquid transportation.

To explore the synergistic effect of the hard phase and the ductile binder phase in hardmetal substrate to the coatings, a binderless WC–6Mo2C–0.68Cr3C2–0.37VC (bWC) model alloy and a WC–10Co–0.65Cr3C2–0.35VC reference alloy with similar grain size (~0.4 μm) were used as substrates. Ti0.94Si0.06N/TiAlSiN/Al0.52Ti0.48N coating was deposited by DC magnetron sputtering. Scratch testing (loading range 0–30 N) results show that complete removal of the coating on bWC substrate occurs under a substantially higher critical load LC2 (28.3 N vs. 21.4 N), but accompanied by a quite earlier cohesion failure expressed by LC1 (LC2 − LC1 = 16.4 N vs. 1.0 N). To reveal the reason behind the high adhesion strength, phase interfaces between AlTiN and WC/Mo2C based phase in bWC substrate were investigated by HRTEM. Coherent and semi-coherent epitaxial growth relationships at the AlTiN/WC interfaces and semi-coherent epitaxial growth relationships at the AlTiN/Mo2C interfaces are easily identified. The minimum lattice misfit (1.9%) is observed when AlTiN growths on (0001)WC along its 4 ¯ 2 2 ¯ direction. The reasons behind the related phenomena are discussed.

Studies have been carried out to increase the adhesion and heat resistance of insulating tape coatings based on chlorobutyl rubber applied on pipelines. It is shown that the synergistic effect of the growth of adhesion of chlorobutyl rubber to steel by the co-administration of the oligomer of 2,2,4-trimethyl-1,2-dihydroquinoline and polymeric petroleum resin is due to the increased interaction of the oligomer with chlorobutyl rubber under the action of a polymeric petroleum resin and the high adhesion of the oligomer to steel.

The problem of obtaining defect-free, corrosion-resistant, glass-enamel coatings for steel pipelines is now high-priority. The composition of a corrosion-resistant coating for steel pipes has been developed and the technical and operational properties of the synthesized glass-enamel coatings investigated. The compositions developed for enamel coatings exhibit high adhesion and chemical resistance to corrosive media and can be recommended for use in the production of enameled pipes.

The engineering of catechol-based hydrogels to bind to wet biological tissues with high adhesion energy remains a challenge. Herein, fast quinone-nucleophile coupling and dynamic boronate ester bond were used to enhance the interfacial adhesion and bulk cohesion of our dual-crosslinked hydrogels, respectively, for fabricating mussel-mimetic tough adhesives.

In this communication, we present a simple and robust switchable dry adhesion system by using PDMS wrinkled-gecko surface. The PDMS substrate with gecko-inspired wide-tip arrays is a wrinkled area generated by UVO exposure using a shadow mask. The fabricated PDMS wrinkled-gecko device shows high dry adhesion hysteresis on a targeted surface. In the experiments, the difference of adhesion force of wrinkled PDMS surface between adhesion on and off modes increases with longer UVO treatment time. Also, it has durability with mechanical robustness without any defect or decrease in adhesion force even after 100 repeating cycles of the adhesion test. These remarkable properties can be used for precise, green-environmental transporting system with various applications in commercial and research areas.

High throughput and high sensitivity are two important aspects in multiple biomarker recognition, drug discovery and relevant biochemical sensing. Here, we integrate mini-pillar microarray with the circuit components toward high-throughput individual electrochemical sensing in microdroplets. On such droplet-microarray-based electrochemical platform, the high adhesion of the mini-pillar can hold a microdroplet (hundreds nanoliter to a few microliter) regardless of rotation and deformation. Each pillar as a unit has a three-electrode to achieve individual electrochemical sensing, and electrodes are integrated on one side to achieve the sequential electrochemical read-out. Qualitative and quantitative electrochemical assessments of multiple glucose concentrations in individual microdroplets are also achieved. Such mini-pillar-based individual electrochemical platform shows great potential in high-throughput and high-sensitive biomolecular recognitions, provides an opportunity to develop miniaturized sensing platform for emerging biological and pathological applications.

Surfaces combining antispreading and high adhesion can find wide applications in the manipulation of liquid droplets, generation of micropatterns and liquid enrichment. To fabricate such surfaces, almost all the traditional methods demand multi-step processes and chemical modification. And even so, most of them cannot be applied for some liquids with extremely low surface energy. In the past decade, multiply re-entrant structures have aroused much attention because of their universal and modification-independent antiadhesion or antipenetration ability. Unfortunately, theories and applications about their liquid adhesion behavior are still rare. In this work, inspired by the springtail skin and gecko feet in the adhered state, it is demonstrated that programmable liquid adhesion is realized on the 3D-printed micro doubly re-entrant arrays. By arranging the arrays reasonably, three different Cassie adhesion behaviors can be obtained: I) no residue adhesion, II) tunable adhesion, and III) absolute adhesion. Furthermore, various arrays are designed to tune macro/micro liquid droplet manipulation, which can find applications in the transportation of liquid droplets, liquid enrichment, generation of tiny droplets, and micropatterns.

Studies have been carried out to obtain a composite multilayer solid lubricant coating of a given thickness capable of operating under extreme operating conditions: a wide range of temperatures, constant and dynamic loads, as well as in vacuum. The composite multilayer solid lubricant coating under study consists of several layers, where each layer has its specified thickness. The layer applied to the base (the first layer of the multilayer coating) is a coating obtained by chemical deposition, has a predetermined thickness of up to 35 microns. The layer applied to the first layer is a phosphate coating of a given thickness up to 12 microns. The third layer applied to the second layer is a coating of a phosphate binder with fillers having a predetermined thickness of up to 100 microns. Each layer performs certain functions.There has been developed the technology of obtaining a composite multilayer solid lubricant coating of a given thickness, which has high adhesion to the base, low coefficient of friction, which can significantly increase the wear resistance of steel products when working under high temperatures and high loads.Tribotechnical tests have revealed the optimal thickness of the composite multilayer solid lubricant coating, which provides maximum wear resistance of the coating when working in tribocoupling.

Recently, nanomaterial-based adhesives have arised as alternatives to be used in the industrial field or to provide the next generation of biomedical adhesives with their enhanced mechanical properties and adhesion strengths. In this work, we developed a method for achieving adhesion between two PDMA (Poly dimethylacrylamide) hydrogel surfaces by using different nanomaterial-based adhesive dispersions with different sizes and shapes that have high mechanical adhesion strength. We obtained a new adhesive consisting of a lipid-based nanotube formed by the special custom-made molecule AQua (C25H29NO4) and measured the adhesion force between the hydrogel surfaces. Our results revealed that lipid AQua nanotube dispersions, which also has a high potential as drug delivery agents, showed efficient adhesion by strongly binding the hydrogel strips together and exhibit better adhesive effects in comparison with other nanomaterials that are used for this purpose. This high adhesion capability is also valid for various hydrogels that have different chemical properties or rigidities and soft tissues such as calf livers. So, the system developed here is believed to have a usage potential in different industrial and biomedical areas.

Over the course of biological evolution, many classes of living creatures have developed highly effective adhesive mechanisms that allow them to attach to various kinds of surfaces having different physical natures and topographies. The most famous instance of this is the gecko pad, but many similar examples are found in animals of different sizes and evolutionary lineages. In recent decades, such adhesive structures have become the objects of intensive theoretical and experimental studies, partly due to research aimed at developing and producing artificial surfaces with similar adhesive properties. Here, we present a review of research on biological structures with high adhesion and high friction. We focus our attention on one particular class of such structures: systems with elastic fibers interacting with rough surfaces. Other structurally similar systems are discussed as well.

Self-recovering superhydrophobic coatings (SHCs) have drawn much attention in recent years because of their unique self-recovering properties and potential industrial applications. In this study, self-recovering SHCs based on recovery of structural damage have been successfully fabricated by spraying the mixture of polymethylmethacrylate/zinc stearate/stearic acid. The SHCs display a static contact angle (CA) of 158°, a sliding angle (SA) of 1° and exhibit a rough structure as shown in the SEM images. By acid rain (pH ≈ 3.5) scouring, the coatings maintain CA of 134° and high adhesion due to the broken morphology. Interestingly, the coatings restored superhydrophobicity after immersion in water for several minutes. Furthermore, the SHCs exhibit good long-term stability, water-durability and UV-durability, adapting to out-door environment. Above all, the coatings are environmental, low cost and can be quickly coated on various large-scale substrates, which will widen their practical applications.

Binary nanoscale interfacial materials are fundamental issues in many applications for smart surfaces. A binary nanoscale interface with binary surface morphology and binary wetting behaviors has been prepared by a facile wet-chemical method. The prepared surface presents superhydrophobicity and high adhesion with the droplet at the same time. The composition, surface morphology, and wetting behaviors of the prepared surface have been systematic studied. The special wetting behaviors can be contributed to the binary nanoscale effect. The stability of the prepared surface was also investigated. As a primary application, a facile device based on the prepared binary nanoscale interface with superhydrophobicity and high adhesion was constructed for microdroplet transportation.

The Chinese fire belly newts (Cynops orientalis) have the ability to escape from the glass tank with vertical walls. An experimental device was developed to investigate the sticking and climbing behaviors of the newts. The detaching angles of the newt on the surfaces of glass, PMMA, and SUS 304 stainless steel at dry, little-water, and plenty-water conditions were measured and used as an index to evaluate the sticking and climbing abilities of the newts on tilted surface. The experimental results show that the newts have a strong ability to stick on tilted surface, particularly on the surface with little water. Morphological studies of the toe pads and belly were carried out by SEM and cryo-SEM to clarify the sticking mechanisms. It is found that the toe pad of the newt consists of a dense array of nanopillars with ca 100 nm – 300 nm diameter surrounded by small channels. This structure is supposed to facilitate high adhesion to substrate by providing capillary forces, and promote the squeeze-out of fluid between the toe pad and substrate in flooded case.

Graphene oxide (GO) can be applied as a coating on metals, but few of these coatings have an adhesion suitable for practical applications. We demonstrate here how to form a GO coating on metals with a high adhesion (∼ 10.6 MPa) and tuneable surface, which can be further applied using similar/modified techniques for special applications (e.g. anti-corrosion and anti-biofouling).

In the present work, we devised a facile, and environmental imprinting and hot-water treatments for developing a durable self-cleaning aluminum surface. The micro and nanostructured surfaces were composed of pillars and ellipsoidal flakes, respectively. The fluorination (vapor deposition) of surfaces imparted superhydrophobicity ( θ s > 150°), with high adhesion observed for micro-patterned surface, while nano and hierarchical surfaces exhibited low hysteresis and tilting angles ( θ Δ E = - 0.3 J / m ) surface has shown the prevalence of stable Cassie state compared to hierarchical ( Δ E = - 0.07 J / m ) counterpart. The nanostructured surface has also exhibited higher durability under static and dynamic conditions than the hierarchical counterpart.

It suffers from poor adhesion to deposit diamond films on steel by using normal metal compound films as an interlayer. Here, high adhesion diamond films were successfully prepared on stainless steel by using Cr/CrSiN nanocomposite film as interlayer. The results show that with Si contents increasing to 10.6 at.%, spikes appear at the interface between diamond films and interlayer, exhibiting high adhesion with hardness increasing to 80 GPa. With Si contents further increasing to 15.5 at.%, the spikes disappear and diamond film peels off even though its hardness still keeps 62 GPa. This indicates that spikes, composed of Cr-C compounds, supply mosaic structure and mechanical lock effects to improve the adhesion. The spikes’ composition means that carbon atoms react with Cr/CrNx crystals in interlayer during HFCVD. Under lower Si contents, amorphous SiNx/Si phases are few, Cr/CrNx crystals can easily react with carbon atoms via different velocities, causing the co-existence of longer and shorter Cr-C phase to form the spikes. As Si content increases, more amorphous phases envelop the crystals, limiting the reaction of carbon atoms with Cr/CrNx crystals, so the spikes disappear. This supplies a way to control the adhesion of diamond films by adjusting Si contents to produce different interface structures.

Superhydrophobic surfaces with either low or high adhesion have great significance in numerous engineering domains. Salvinia, a common aquatic plant which has hydrophobic micro hair with a hydrophilic tip on the top, is a nature superhydrophobic surface with high adhesion. Here, inspired by salvinia, a superhydrophobic surface with high adhesion is fabricated by simple polymerization of dopamine (DA) onto nanotips of micro/nanostructured superhydrophobic surface. When the rough superhydrophobic surface is immersed in the DA solution, air is trapped in valley between the micro/nanostructures and discontinuous three-phase contact line (TCL) forms immediately. The polydopamine (PDA) adhesion only occurs on very tips of the micro/nanostructures, while the other ravine part of the micro/nanostructures remained hydrophobic, what endows the superhydrophobic surface numerous hydrophilic tiny tips like the hairs of salvinia leaf. The salvinia-like surface showed superhydrophobic but high adhesive property. This work unfolds more applicabilities of superhydrophobic surface and promotes the application of the superhydrophobic surface.

In situ electrochemical atomic force microscopy (ec-AFM) is utilised for the first time to probe the initial stages of metal-organic framework (MOF) coating growth via anodic dissolution. Using the example of the Cu MOF HKUST-1, real time surface analysis is obtained that supports and verifies many of the reaction steps in a previously proposed mechanism for this type of coating growth. No evidence is observed however for the presence or formation of Cu2O, which has previously been suggested to be both key for the formation of the coating and a potential explanation for the anomalously high adhesion strength of coatings obtained via this methodology. Supporting in situ electrochemical Raman spectroscopy also fails to detect the presence of any significant amount of Cu2O before or during the coating's growth process.

The unique pattern of pitcher plants inner surface and its super-antiwetting property with high adhesion is reported. The surface is replicated by using a two-step approach with PDMS as the replicating material. The replica showed similar surface morphology and surface properties.

International audience; Here, we report the possibility to obtain superoleophobic properties (contact angle sunflower oil = 150° and contact angle hexadecane = 136°) with high adhesion, by electrodeposition of conducting polymer containing short perfluorobutyl (C4F9) chains on stainless steel meshes. To obtain such properties, it is necessary to render stainless steel meshes sufficiently rough by applying a high deposition charge (Qs = 225 mC.cm-2) to deposit polymer micro/ and nanostructures around the holes of the mesh. We also show that the mesh opening is extremely important and that the best mesh opening is 100 microns (we tested from 25 microns to 800 microns). These results are exceptional with polymer containing C4F9 chains and open new strategies to design fluorinated materials with low bioaccumulative potential.

With the rapid development of the advance integrated circuit (IC) packaging, adhesion between epoxy molding compound (EMC) and leadframes has been defined as one of the most key factors influencing the reliability of integrated circuit, especially with the packages with the Pd(PPF's) pated leadframes. The objective of this work was to study an epoxy molding compound with high adhesion on PPFs as well as good moldability. In this study three different types of epoxy resins (showed in Figure1), hardeners (showed in Figure2) and catalysts were investigated. It was found that epoxy resin B showed higher adhesion on Ag while epoxy resin A as the lowest. The composition of A/B/C as the epoxy resin exhibited higher adhesion on PPF. Hardener E and F exhibited high adhesion on PPF especially hardener E, and further on, hardener E possess lower DMA modulus and Tg than the other two hardener. While hardener F shows the highest adhesion on Ag. When using the composition E/F as hardener, the adhesion on PPF was as high as that hardener E. EMC with phosphorous catalyst in disclosed lower water absorption than that with imidazole one in. The latent phosphorous catalyst showed higher HH and higher adhesion on Ag and PPF that the other two catalysts.

High-adhesion stretchable electrodes are fabricated by utilizing a novel nanopile interlocking strategy. Nanopiles significantly enhance adhesion and redistribute the strain in the film, achieving high stretchability. The nanopile electrodes enable simultaneous monitoring of electromyography signals and mechanical deformations. This study opens up a new perspective of achieving stretchability and high adhesion for stretchable electronics.

Patterning metal films on various substrates is essentially important and yet challenging for developing a wide variety of innovative devices. We herein report a versatile approach to pattern metal (gold, silver, or copper) films on arbitrary substrates by using the bio-inspired polydopamine (PDA) thin film as a UV-sensitive adhesive layer for electroless deposition. The PDA film is able to be formed on virtually any solid surfaces under mild condition, and its rich catechol groups allow for electroless deposition of metal films with high adhesion stability. Upon UV irradiation, spatially selective oxidation of PDA film occurs and the local metal deposition is inhibited, thus facilitating successful patterning of metal films. Considering its versatility and simplicity, this strategy may demonstrate great applications in manufacturing various innovative devices.

A three-dimensional superhydrophobic copper 7,7,8,8-tetracyanoquinodimethane (CuTCNQ) nanowire array with the capability of high adhesion of osteoblasts was demonstrated. The CuTCNQ nanowire array was constructed by using a combined vapor deposition technique. The superhydrophobic nanowire array exhibited very high adhesion of osteoblasts, indicating that the CuTCNQ nanowire array was a good biointerface.

While adhesion reduction due to roughness is not surprising, roughness induced adhesion remained a puzzle until recently Guduru and coworkers have shown a very convincing mechanism to explain both the increase of strength and of toughness in a sphere with concentric single scale of waviness. Kesari and coworkers have later shown some very elegant convenient asymptotic expansion of Guduru's solution. This enhancement is very high and indeed, using Kesari's solution, it is here shown to depend uniquely on a Johnson parameter for adhesion of a sinusoidal contact. However, counterintuitively, it leads to unbounded enhancement for conditions of large roughness for which Johnson parameter is very low. Guduru postulated that this enhancement should occur after sufficiently large pressure has been applied to any spherical contact. Also, that although the enhancement is limited to the JKR regime of large soft materials with high adhesion, the DMT limit for the smooth sphere is found otherwise. However, for hard materials, even the DMT limit for the smooth solids is very hard to observe, which suggest that also adhesion reduction is yet not well understood. The limitations of the assumption of simply connected area is here further discussed, and a well known model for hard particles in contact with rough planes due to Rumpf is used to show that in the range where unbounded increase is predicted, orders of magnitude reduction is instead expected for rigid solids. We suggest that Guduru's model may be close to an upper bound to adhesion of rough bodies, while the Rumpf-Rabinovich model may be close to a lower bound., Comment: 8 pages