Permanent Adhesion Research Articles

Peridynamics simulation of microparticle impact: Deformation, jetting, and the influence of surface oxide layer

Over the past decade, cold spraying (CS) has become a significant additive manufacturing technology for creating metallic structures and repairing damaged components. This study uses a novel peridynamic model to investigate the behavior of 12 μm copper particles impacting a copper substrate during CS deposition. The model examines deformation behavior, material jetting, and the effect of a native particle oxide layer. Two oxide thicknesses, 6 nm and 30 nm, were considered. The 6 nm oxide, typical for gas-atomized copper powders, had a negligible effect on deformation, while the 30 nm oxide showed a notable influence. For the 30 nm oxide, the experimentally observed coefficient of restitution (COR) deviated from theoretical predictions in the velocity range of 400–600 m/s due to cracking and fracturing of the oxide layer at higher impact velocities, reducing particle rebound velocity without sufficient metal-to-metal contact for permanent bonding. Permanent adhesion requires significant oxide fragmentation and separation. The study also identified threshold velocities for material jetting from the substrate and particle, showing that oxide presence delays particle jetting by impeding plastic deformation at the edges. Quantifying the oxide volume at the particle-substrate interface clarifies the effect of jetting on COR and bonding strength. The analysis includes effects of deflected jets at extremely high velocities (e.g., 870 m/s), compared with existing literature. Overall, the results demonstrate the efficacy of the peridynamics-based simulation in accurately representing material behavior during high-velocity impacts, effectively predicting oxide breakup, detachment, and removal in CS, and their effects on deposition characteristics.

Deciphering protein-mediated underwater adhesion in an invasive biofouling ascidian: Discovery, validation, and functional mechanism of an interfacial protein

Discovering macromolecules and understanding the associated mechanisms involved in underwater adhesion are essential for both studying the fundamental ecology of benthos in aquatic ecosystems and developing biomimetic adhesive materials in industries. Here, we employed quantitative proteomics to assess protein expression variations during the development of the distinct adhesive structure - stolon in the model fouling ascidian, Ciona robusta. We found 16 adhesive protein candidates with increased expression in the stolon, with ascidian adhesive protein 1 (AAP1) being particularly rich in adhesion-related signal peptides, amino acids, and functional domains. Western blot and immunolocalization analyses confirmed the prominent AAP1 signals in the mantle, tunic, stolon, and adhesive footprints, indicating the interfacial role of this protein. Surface coating and atomic force microscopy experiments verified AAP1′s adhesion to diverse materials, likely through the specific electrostatic and hydrophobic amino acid interactions with various substrates. In addition, molecular docking calculations indicated the AAP1′s potential for cross-linking via hydrogen bonds and salt bridges among Von Willebrand factor type A domains, enhancing its adhesion capability. Altogether, the newly discovered interfacial protein responsible for permanent underwater adhesion, along with the elucidated adhesion mechanisms, are expected to contribute to the development of biomimetic adhesive materials and anti-fouling strategies. Statement of SignificanceDiscovering macromolecules and studying their associated mechanisms involved in underwater adhesion are essential for understanding the fundamental ecology of benthos in aquatic ecosystems and developing innovative bionic adhesive materials in various industries. Using multidisciplinary analytical methods, we identified an interfacial protein - Ascidian Adhesive Protein 1 (AAP1) from the model marine fouling ascidian, Ciona robusta. The interfacial functions of AAP1 are achieved by electrostatic and hydrophobic interactions, and the Von Willebrand factor type A domain-based cross-linking likely enhances AAP1’s interfacial adhesion. The identification and validation of the interfacial functions of AAP1, combined with the elucidation of adhesion mechanisms, present a promising target for the development of biomimetic adhesive materials and the formulation of effective anti-fouling strategies.

Solvent-free urethane-based prepolymer as a versatile underwater adhesive material

High bonding strength and water resistance have always been the top priority in developing most reported man-made underwater adhesives; however, easy delivery, low solvent toxicity, and long working times are equally important for many applications, particularly for the development of sustainable and green bonding processes. In this study, we explored the use of a solvent-free urethane-based prepolymer that initially behaves like a pressure-sensitive adhesive that works underwater, then cures for stronger permanent adhesion. These favorable properties are obtained by carefully balancing adhesive functionality, viscoelasticity, and inter-chain interactions. The resulting synthetic prepolymer adhesive material is a viscous semi-solid consisting of isocyanate-capped polymers bearing carboxyl and urethane groups as the potential sites of non-covalent and covalent interactions. Such a sticky adhesive can be easily deposited and has instant adhesion on various flat/curved substrates. It continues to strengthen over a curing time of nearly 2 days, reaching a comparable bonding strength of around 1.2 MPa and peel adhesion of around 2300 N m−1 on aluminum sheets. The prolonged curing process allows for enough time for various applications, such as operating the underwater sealing of fractured items and bonding string to mussel shells. The easy delivery, eco-friendly nature, and initial adhesion of this adhesive provide great opportunities for application in engineering and aquaculture fields.

Synthesis and characterization of sesame oil based plasticizers for reversible bonding in thermally detachable polyurethane adhesives

Permanent adhesion causes immense problem during repairing of expensive components in electronics and automotive industries. Adhesives that can be reversibly debonded upon stimulus are a popular solution to this issue in the present day. Here, we report the synthesis of an eco-friendly polyurethane hot-melt detachable adhesives (HMDA) that uses oxime-carbamate bonding and is derived from natural and modified polyols from sesame seed oil. With the help of catalyst dibutyltin dilaurate (DBTDL), polyols and dimethyl glyoxime has been polymerized with toluene diisocyanate (TDI) and glycerin. FTIR, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) have been used to analyze prepared adhesives. Out of prepared samples, a very minute amount of hydroxylated sesame oil based sample (S3) has shown good binding strength with glass surface, having load capacity of 200 g/12 h and can be used repeatedly for >20 cycles.

THE ROLE OF ANTICOAGULANT, THROMBOLYTIC, AND FIBRINOLYTIC ACTIVITIES IN THE PREVENTION OF PERITONEAL ADHESION

Peritoneal adhesion occurs as a result of surgery, peritoneal injury, peritonitis, hypoxia, and ischemia. Surgical trauma causes many pathophysiological processes which include inflammation, oxidation, coagulation, fibrinolysis, cell proliferation, and apoptosis. After intra-abdominal operations, the adhesion tissue may occur on the peritoneal surface due to low fibrinolytic activity. This may result in permanent excessive adhesion tissue bands instead of properly formed fibrin structures. Therefore, anticoagulant, thrombolytic, and fibrinolytic activities have a key role in preventing peritoneal adhesion. Indeed, several studies have been conducted to find out new and effective agents against intra-abdominal adhesion. Thus, revealing the causes, development processes, and investigation techniques are highly important for designing and conducting such scientific studies. In this context, this study aims to summarize the pathophysiological processes of above-mentioned activities and to emphasize their importance in the peritoneal adhesion model as well as to explain the evaluation methods, particularly in terms of the investigation of natural products.

Mechanical reinforcement of waterborne latex pressure‐sensitive adhesives with polymer‐grafted nanoparticles

AbstractWaterborne pressure sensitive adhesives (PSAs) consisting of polymer microparticle emulsions (i.e. latex) are more commonly used in commercial applications than solvent‐borne alternatives, as the use of water as a suspension medium provides better consumer safety and reduces environmental impact. However, the lower mechanical performance of waterborne PSAs prevents their use in applications requiring permanent adhesion or strong bonding between substrates. This reduction in mechanical strength is often attributed to void spaces that form during water evaporation and coalescence of the latex particles, and thus a potential strategy to improve PSA strength would be to add filler materials to occupy these voids. Fundamental studies investigating how interfacial interactions between the latex and fillers affect the collective strength of the films would enable better design of adhesive compositions to tailor PSA mechanical properties. Here we report the use of polymer brush‐grafted nanoparticles (PGNPs) as a means of mechanically reinforcing the PSAs, and determine how different aspects of the particle and polymer brush designs enable this improvement in adhesive performance. The PGNPs investigated here are intentionally designed to phase segregate into the aqueous phase of the initial latex suspension, which allows them to both fill free pore volume and also form multivalent supramolecular interactions with the latex particles to form polymer bridges that improve the interconnectivity of the final film. These studies provide insight into potential design strategies for tuning PSA properties with PGNPs, and enable up to 32% improvements to the cohesive strength of the PSAs without the typical deterioration of adhesive strength observed in PSAs using non‐brush‐coated particle fillers.

Subsurface impact damage imaging for composite structures using 3D digital image correlation

An integrated system is proposed to visualize subsurface barely visible impact damage (BVID) in composite structures using three-dimensional (3D) digital image correlation (3D DIC). This system uses a pair of digital cameras to record video frames in the field-of-view (FOV) of the structure’s surface, capturing the wavefield generated via chirp excitation in the near-ultrasonic frequency range. Significant pitfalls of previous efforts of damage imaging using two-dimensional DIC have been largely mitigated. First, 3D DIC enables capturing out-of-plane displacements, which are much larger in amplitude versus in-plane displacements that a single camera would be limited to sensing, thus increasing the signal-to-noise ratio. This enhancement in turn increases the sensitivity of the stereo-camera system. Second, a total wave energy (TWE) damage imaging condition is proposed to visualize the local damage region. The monogenic signal obtained via Reisz transform (RT) is employed to compute the instantaneous amplitude, with which the local wave energy can be calculated spatially over time. Since a high displacement amplitude and thus high wave energy will occur in the damage region due to the local resonance, the proposed TWE imaging condition can relax the Nyquist sampling requirement, unlike guided-wave-based structural health monitoring techniques which require fully reconstructing the wavefield and wave modes through sampling that satisfies the Nyquist criterion. As such, a much lower camera frame rate is adequate for the proposed system. Consequently, the maximum spatial resolution of the camera for a given FOV can be achieved at the expense of a reduced frame rate. With the maximized pixel resolution and reduced frame rate for employing the TWE imaging condition, composite structures can be inspected or monitored with a larger FOV. As a result, there is no longer any need to apply signal enhancement techniques, such as sample interleaving, image stitching, or averaging, to increase the effective performance of the camera. Rather than needing thousands of repeated videos for minimizing the incoherent noise, only a single stereo-video with a few seconds of sampling duration is necessary for damage imaging. The use of a powerful piezo-shaker also increases the wave signal amplitude and further enhances sensitivity without permanent adhesion. To demonstrate this stereo-camera concept with the TWE imaging condition, the system was used to image damage in two carbon fiber reinforced polymer composite honeycomb panels, which had been subjected to low-velocity impacts (2 J). For each panel, two excitation configurations were used to verify the robustness of the system. Initial damage maps produced for a 100 × 100-mm FOV using a three-second stereo-video show accurate damage imaging ability that is independent of excitation location and comparable to benchmark damage images computed from laser Doppler vibrometer data and those gathered from ultrasonic and X-ray computerized tomography scans. This efficient and reliable integrated system demonstrated high potential for in-time damage inspection on composite aircraft and other critical structures.

Biocompatible Optical Fibers Made of Regenerated Cellulose and Recombinant Cellulose-Binding Spider Silk

The fabrication of green optical waveguides based on cellulose and spider silk might allow the processing of novel biocompatible materials. Regenerated cellulose fibers are used as the core and recombinantly produced spider silk proteins eADF4(C16) as the cladding material. A detected delamination between core and cladding could be circumvented by using a modified spider silk protein with a cellulose-binding domain-enduring permanent adhesion between the cellulose core and the spider silk cladding. The applied spider silk materials were characterized optically, and the theoretical maximum data rate was determined. The results show optical waveguide structures promising for medical applications, for example, in the future.

Most kompozytowy modelowany bezpośrednio – obserwacja 15-letnia

The practical combination of the potential of bonding systems, composite materials and synthetic fibres opens up new possibilities for the restoration of qualitative and quantitative deficiencies. The use of a fibre filler significantly changes the mechanical properties of the composite material. This study presents the restoration of missing tooth 24 with a fibre-reinforced composite bridge. As a bridge pillars were used: tooth 23 – after endodontic treatment and tooth 25 – with preserved vitality and fixed filling covering the proximal wall and chewing surface. The work was carried out by direct modelling in the oral cavity. The restoration was made from two different types of composite material: a light-curing and a light-chemically-curing dual-activation polymerisation system. The materials use a different filler and matrix. The structure was reinforced with 16,000 glass fibres arranged in parallel. Systematic check-ups and periodic prophylactic treatments avoided complications and preserved function over a 15-year follow-up time. The methods and materials used allowed to achive permanent adhesion and functional-aesthetic restoration of the quantitative deficit of 24 and qualitative deficiencies of teeth 23 and 25. Fifteen years of observations confirmed the effectiveness and durability of the used solution.

3D printed membrane‐integrated spacers for enhanced antifouling in ultrafiltration

AbstractFeed spacers are an important component of membrane‐based filtration systems as they promote turbulence and mass transfer during the filtration process—thereby, reducing the membrane fouling and improving the flux. Whereas spacers are used as a separate component in conjunction with membranes, herein, we demonstrate that membrane‐integrated spacers offer superior fouling resistance and hence an improved output flux during filtration. The integrated spacers were fabricated by 3D printing a composite slurry of UV curable resin and polyvinylidene fluoride on the Polyethersulfone‐based ultrafiltration (UF) membrane. After curing under the UV light, the 3D printed spacers showed excellent flexibility and mechanical integrity along with permanent adhesion to the UF membrane. When tested for filtration using humic acid as foulant, the integrated spacer offered significantly reduced fouling and an increased flux as compared with the commercial spacer. Moreover, it was found that the geometry of the integrated spacers plays an important role in their performance. Among different geometries, the “gyroid” geometry, with an optimal infill density, provided the highest fouling resistance while improving the flux by nearly 150% as compared with the commercial spacer. When tested as stand‐alone spacers, the 3D spacers with identical geometries resulted in an increased fouling and lower flux which confirmed the superior performance of membrane integrated spacers.

Electro-Thermally Actuated Non-Volatile Mechanical Memory With CMOS-Level Operation Voltage and Low Contact Resistance

A non-volatile mechanical memory device with CMOS-level operation voltage and low contact resistance is proposed utilizing electro-thermal actuation method for the first time. Unlike the most widely used electrostatic actuation method in microelectromechanical systems (MEMS) devices, electro-thermal actuation is known to produce large actuation force and displacement with low operation voltage, which are preferable attributes of a mechanical memory. In addition, stiction, one of the most notable failure mechanisms of MEMS devices referring to the inadvertent permanent adhesion between two surfaces, can be exploited to significantly improve the energy efficiency of mechanical memory by retaining the ON-state without power. We devised a non-volatile mechanical memory device capable of performing multiple cycles of write and erase operations with CMOS-level voltage by utilizing electro-thermal actuation and stiction. The fabricated electro-thermally actuated mechanical memory successfully performed 200 repeated cycles of write and erase operations at 0.9V and 1.0V, respectively. Thanks to the high contact force generated by electro-thermal actuation, the fabricated device achieved the contact resistance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$17 \boldsymbol {\Omega }$ </tex-math></inline-formula> . Lastly, we confirmed that the fabricated device successfully retained both ON and OFF states upon removal of power beyond 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> seconds. [2021-0178]

Getting a Grip on the Adhesion Mechanism of Epiphytic Orchids – Evidence From Histology and Cryo-Scanning Electron Microscopy

Plants and animals evolve different attachment structures and strategies for reversible or permanent adhesion to different substrate types. For vascular epiphytes, having the ability to permanently attach to their host plants is essential for establishment and survival. Unlike mistletoe roots, roots of vascular epiphytes do not penetrate the host tissues but instead achieve attachment by growing in close contact to the surface of the substrate. However, the fundamental understanding of the attachment functions of epiphytic roots remains scarce, where majority of studies focused on the general root morphology, their functional properties and the descriptions of associated microbial endophytes. To date, research on attachment strategies in plants is almost entirely limited to climbers. Therefore, this study aims to fill the knowledge gap and elucidate the attachment functions of roots of epiphytic orchids. With the use of histology and high-resolution cryo-scanning electron microscopy (cryo-SEM) technique with freeze fracturing, the intimate root-bark substrate interface of epiphytic orchid Epidendrum nocturnum Jacq was investigated. Results showed a flattened underside of the root upon contact with the substrate surface, and the velamen layer appeared to behave like a soft foam, closely following the contours of the substrate. Root hairs emerged from the outermost velamen layer and entered into the crevices in the substrate, whenever possible. A layer of amorphous substance (glue-like substance) was observed on the surface of the root hairs. Combining the observations from this study and knowledge from previous studies, we hypothesised that epiphytic orchid roots produced a layer of glue-like substance to adhere the root to the substrate. Then root hairs are produced and enter into the voids and crevices of the substrate. This further generates a mechanical interlocking mechanism between root and substrate, thus reinforcing the attachment of the root (and hence the whole plant) to its substrate.

Effect of upstream priming on transient downstream platelet-substrate interactions

Upstream exposure of platelets to activating proteins ‘primes’ platelets for increased downstream adhesion, though the mechanics of platelet translocation before permanently arresting are not well understood. To investigate platelet translocation on platelet-binding proteins, primed platelets’ transient contacts with immobilized proteins were recorded and analyzed. Using a microfluidic channel, representative of a vascular graft, platelet-activating proteins were covalently attached to the upstream priming, center, and downstream capture positions. Image sequences of platelet interactions with the center protein were captured as platelet-rich plasma (PRP) was perfused through the channel. There was an increase in both platelet pause events and net platelet adhesion on von Willebrand factor, collagen, or fibrinogen following upstream exposure to the same protein. Upstream priming also caused a decrease in average platelet velocity. The duration of transient platelet arrests on the protein-coated surface and the distance that platelets travel between pause events depended on the protein with which they were interacting. The most significant increase in platelet pause events frequency and decrease in average velocity occurred on immobilized von Willebrand factor, compared to the control with no upstream priming. These results demonstrate that platelet priming increases downstream platelet-protein interactions prior to permanent adhesion.

Raising the permanent adhesion of coatings on resinous wood by APPCVD promotion

Some resinous woods are preferred for outdoor use due to their durability and long-term stability. Nevertheless, resinous woods are known to generate trouble with coating adhesion after a certain time in outdoor use, resulting in coating detachment and/or microbial infestation. To overcome this problem, the application of atmospheric pressure plasma chemical vapour deposition (APPCVD) as primer – instead of a commercially available impregnation agent – was established to raise the permanent adhesion of a subsequent applied functional coating, such as glaze or lacquer. Results regarding blue stain protection and long-term stability of the resinous woods larch, Douglas fir, and Scots pine protected by an APPCVD primer and a subsequent layer of glaze/lacquer are discussed. This is also done in comparison to a state-of-the-art protection.

Biochemistry of Barnacle Adhesion: An Updated Review

Barnacles are notorious marine fouling organisms, whose life cycle initiates with the planktonic larva, followed by the free-swimming cyprid that voluntarily explores and searches for an appropriate site to settle and metamorphoses into a sessile adult. Within this life cycle, both the cyprid and the adult barnacle deposit multi-protein adhesives for temporary or permanent underwater adhesion. Here, we present a comprehensive review of the biochemistries behind these different adhesion events in the life cycle of a barnacle. First, we introduce the multiple adhesion events and their corresponding adhesives from two complementary aspects: the in vivo synthesis, storage, and secretion as well as the in vitro morphology and biochemistry. The amino acid compositions, sequences, and structures of adult barnacle adhesive proteins are specifically highlighted. Second, we discuss the molecular mechanisms of adult barnacle underwater attachment in detail by analyzing the possible adhesive and cohesive roles of different adhesive proteins, and based on these analyses, we propose an update to the original barnacle underwater adhesion molecular model. We believe that this review can greatly promote the general understanding of the molecular mechanisms underlying the reversible and irreversible underwater adhesion of barnacles and their larvae. Such an understanding is the basis for the prevention of barnacle fouling on target surfaces as well as designing conceptually new barnacle-inspired artificial underwater adhesives.

Tracked Wall-Climbing Robot for Calibration of Large Vertical Metal Tanks

Large vertical metal tanks are the primary vessels for the storage and turnover of crude oil, and the accuracy of their capacity calibrations are of great significance. The optical reference line method (ORLM) is used for capacity calibration and is time-consuming, labor-intensive, and hazardous, because of the elevated work. This paper aims to present a robot to overcome the problems above. We propose a tracked wall-climbing robot (TWCR) with permanent magnetic adhesion tracks, a collapsible scale, and an optional shovel-like rust remover that enable the TWCR to move stably on tank surfaces and perform the ORLM. Two sets of field tests (internal ORLM and external ORLM) indicate that capacity calibration by the TWCR is time saving, convenient, and safe, in addition to being accurate and reliable.

Analysis of Magnetic Wheel Adhesion Force for Climbing Robot

This paper describes the aim of designing, building and testing magnetic wheel based an autonomous climbing robot, for use in conjunction with Non-Destructive Testing (NDT) inspection on vertical towers. Through extensive review of previous generations of climbing robot, a hybrid wheel and permanent magnetic adhesion system has been designed and discussed in this paper. Using mathematical modelling and Finite Element Analysis (FEA) of differing magnet geometries, an adhesion system has been developed to produce the required amount of adhesion force and has been empirically tested at several intervals are presented in this paper. To complement this adhesion system, a lightweight, cost effective body is designed using 3D CAD software and manufactured using rapid prototyping methods. This has been done to incorporate the electronic equipment used to sense the working environment, drive the robot and carry equipment capable of performing defect detection tasks. To do this, a range of sensors, motors and auxiliary equipment has been used and controlled by a microcontroller. Finally, a functional scale prototype are manufactured, assembled and tested on a cylindrical test rig that closely imitated its intended work environment.

Competing with barnacle cement: wetting resistance of a re-entrant surface reduces underwater adhesion of barnacles.

Surfaces with re-entrant topographies can repel liquids even of extremely low surface tension, almost independently of the material's inherent wettability. We show that this topography-based wetting resistance can also be applied to underwater applications, reducing the permanent adhesion of marine hardfouling organisms. Having combined a biofouling assay in the marine environment with microscopic analyses, we demonstrate how a synergistic effect of a soft silicone-based material with a re-entrant mushroom-shaped surface topography strongly increases the fouling release ability of such coatings compared with a smooth control made from the same material. Our coating inhibited the complete wetting of the solidifying glues produced by marine organisms, which resulted in a decreased contact area and, consequently, low adhesion. Our work suggests that topography-induced wetting resistance of surfaces may become a viable approach in preventing permanent adhesion of marine hardfouling organisms.

Bacterial adhesion at the single-cell level.

The formation of multicellular microbial communities, called biofilms, starts from the adhesion of a few planktonic cells to the surface. The transition from a free-living planktonic lifestyle to a sessile, attached state is a multifactorial process that is determined by biological, chemical and physical properties of the environment, the surface and the bacterial cell. The initial weak, reversible interactions between a bacterium and a surface strengthen to yield irreversible adhesion. In this Review, we summarize our understanding of the mechanisms governing bacterial adhesion at the single-cell level, including the physical forces experienced by a cell before reaching the surface, the first contact with a surface and the transition from reversible to permanent adhesion.

Design of permanent magnetic wheel-type adhesion-locomotion system for water-jetting wall-climbing robot

Regular surface-maintenances are necessary for high structures to increase service life. The traditional manual operation has shortcomings like limited maneuverability, poor operating quality, low operating efficiency, and high risk of physical harm, which makes it urgent to develop wall-climbing robot for carrying out surface-maintenances of high structures with high efficiency, low cost, and good protection of operators. In this article, we have developed a wheeled wall-climbing robot that uses a permanent magnet adhesion system to climb on large steel surfaces. Wheel traction to avoid slippage is increased by using inflated rubber tire while maintaining a desired air gap for the magnet system. Research is directed at designing a lightweight magnet system to provide an optimum adhesion force and at determining required tire pressures to maintain a specified air gap between the magnets and the surface.