Low Adhesion Research Articles

Nitrogen-Doped Diamond-like Coatings for Long-Term Enhanced Cell Adhesion on Electrospun Poly(ε-caprolactone) Scaffold Surfaces

Electrospun poly(ε-caprolactone) (PCL)-based scaffolds are widely used in tissue engineering. However, low cell adhesion remains the key drawback of PCL scaffolds. It is well known that nitrogen-doped diamond-like carbon (N-DLC) coatings deposited on the surface of various implants are able to enhance their biocompatibility and functional properties. Herein, we report the utilization of the pulsed vacuum arc deposition (PVAD) technique for the fabrication of thin N-DLC coatings on the surface of electrospun PCL scaffolds. The effect of N-DLC coating deposition under various nitrogen pressures on the morphological, mechanical, physico-chemical, and biological properties of PCL scaffolds was investigated. It was established that an increase in nitrogen pressure in the range from 5 × 10−3 to 5 × 10−1 Pa results in up to a 10-fold increase in the nitrogen content and a 2-fold increase in the roughness of the PCL fiber surface. These factors provided the conditions for the enhanced adhesion and proliferation of human mesenchymal stem cells (MMSCs) on the surface of the modified PCL scaffolds. Importantly, the preservation of N-DLC coating properties determines the shelf life of a coated medical device. The elemental composition, tensile strength, and surface human MMSC adhesion were studied immediately after fabrication and after 6 months of storage under normal conditions. The enhanced MMSC adhesion was preserved after 6 months of storage of the modified PCL-based scaffolds under normal conditions.

Effect of High-Pressure Processing Pretreatment on the Textural Properties of Cooked Nuovo Maratelli Rice

Nuovo Maratelli, a japonica rice with an intermediate amylose content, is suitable for paella (a traditional Spanish dish) due to its ability to withstand cooking and absorb flavors. In this study, high-pressure processing (HPP) at 400 and 600 MPa (10 min) was used as a pretreatment to improve the properties of rice cooked by either boiling or microwaving. The microstructure and pasting properties of unpressurized and pressurized rice were examined. Also, the cooking time and cooking kinetics were determined for each cooking method. Overall, the pasting properties of the rice were not impacted by the HPP treatments, but the typical polyhedral form of the rice starch granules was lost, especially at 600 MPa. Cooking times were reduced from 14 and 10 min for unpressurized samples to 12 and 8 min (400 MPa) and 8 and 6 min (600 MPa) for boiling- and microwave-cooked rice, respectively. The rice pretreated at 400 MPa (10 min) and microwaved (8 min) had lower hardness and adhesiveness, which was linked to the release of amylose during cooking. In summary, HPP could be an effective pretreatment for the improvement of the cooking and textural properties of Nuovo Maratelli rice, particularly when cooked by microwaving.

Field-based investigation of low adhesion leaf layers: Assessing layer initiation and environmental influences

Changing weather conditions are known to impact on adhesion at the railhead. However, the influence on actual leaf layer “seeding” (formation) and low adhesion has not been measured in the field. This paper presents findings from a field survey conducted in autumn 2023 on a narrow gauge railway in Wales, observing leaf layer initiation, development, and environmental influences on adhesion levels. Using friction testing, timelapse imagery, and chemical analysis, the study examines the impact of weather and layer characteristics on friction. Results show that moisture content in the layer has a significant impact on adhesion levels, with a linear relationship observed between moisture and friction. Leaf layer initiation and development were observed, with water playing a crucial role in layer formation. Chemical analysis revealed the presence of iron oxides and biopolymers in the leaf layers. The results give insight into the variation in adhesion levels in leaf layer that have been measured through indirect measures in the past.

Bioactive glass suspension hydrogel promotes wound healing by modulating fibroblasts

The irritation and adhesion of wound healing biomaterials to wet wounds should be addressed for achieving effective wound healing. In this study, a stable multifunctional hydrogels (BGs/HA suspension gels) were prepared using superfine powder of bioactive glasses (BGs), the biocompatible materials hyaluronic acid (HA) and carbomer940, which had good adhesion and low irritation properties for use in moist complex wounds. The average particle size of BGs/HA suspension gels was 13.11 ± 0.29μm, and the BG content was 15.8 ± 0.2% (m m-1). The results of cell proliferation, cell migration, and immunofluorescence staining experiments showed that in the initial stage of wound healing, the ionic extract of BGs formulations promoted the proliferation and migration of L929 cells and induced the secretion ofα-SMA and collagen I. In the final stage of repair, the ionic extract of the BGs formulation regulated the differentiation of fibroblast, which contributed to the reduction of pathological scar formation.In vivoexperiments showed that the wound healing rate of BGs/HA suspension gels group exceeded higher than that of the conventional BGs superfine powder group. Although BGs/HA suspension gels were comparable to its commercially available counterpart (Dermlin paste) in promoting wound healing, it addressed the problem of localized irritation caused by the high pH and low adhesion of BGs products. This study confirmed the specific regulatory effect of BGs/HA suspension gels on L929 cells, which provided a reference for the clinical application of BGs in wound dressing.

Research Progress on Using Modified Hydrogel Coatings as Marine Antifouling Materials

The adhesion of marine organisms to marine facilities negatively impacts human productivity. This phenomenon, known as marine fouling, constitutes a serious issue in the marine equipment industry. It increases resistance for ships and their structures, which, in turn, raises fuel consumption and reduces ship speed. To date, numerous antifouling strategies have been researched to combat marine biofouling. However, a multitude of these resources face long-term usability issues due to various limitations, such as low adhesion quality, elevated costs, and inefficacy. Hydrogels, exhibiting properties akin to the slime layer on the skin of many aquatic creatures, possess a low frictional coefficient and a high rate of water absorbency and are extensively utilized in the marine antifouling field. This review discusses the recent progress regarding the application of hydrogels as an important marine antifouling material in recent years. It introduces the structure, properties, and classification of hydrogels; summarizes the current research status of improved hydrogels in detail; and analyzes the improvement in their antifouling properties and the prospects for their application in marine antifouling.

Environment-tolerant, inherently conductive and self-adhesive gelatin-based supramolecular eutectogel for flexible sensor

Although hydrogels have attracted increasing attention in the stretchable devices, the low adhesion properties and poor environmental adaptation still seriously restrict their development and application. Herein, we focused on the interaction between polymer networks with disperse media and their resultant influence on gel performance, and constructed self-adhesive and environment-tolerant gelatin/polyacrylamide supramolecular-polymer double-network (Gelatin/PAM SP-DN) eutectogels using multiple supramolecular interactions between natural macromolecule and well-designed deep eutectic solvent (DES). The dual networks of Gelatin/PAM SP-DN eutectogels produced significant supramolecular forces with DES, including hydrogen bonding and electrostatic interaction, contributing to enhance the energy dissipation capacity. Additionally, the Gelatin-PAM SP-DN eutectogels were more prone to generate strong bonding force to various substrates, showcasing both in-situ and ex-situ adhesion performance, and even being used for wet and underwater adhesion. The eutectogels revealed excellent environmental tolerance to maintain excellent mechanical flexibility, conductivity and adhesion at high and low temperatures, ensuring the constructed sensor to sensitively and reliably perceive strain, pressure and human motions over a wide temperature range. Also, the eutectogel demonstrated great potential as a temperature sensor. This work opens up a new horizon in the design of multifunctional and environment-tolerant natural macromolecule-based gel materials for flexible electronics, human-machine interaction and health diagnosis.

Bioinspired interfacial engineering of multiscale micro/nano-structured surfaces with robust superhydrophobic and tunable adhesion

Creating superhydrophobic surfaces with varying liquid–solid adhesion holds significant applications in waterproofing, lab-on-chip, and self-cleaning. Biological superwetting surfaces, such as lotus leaf and rose petal, leverage hierarchical micro/nanoscale surface structures together with low-surface-energy chemicals, to synergistically tune their adhesion. However, existing synthetic technologies encounter great difficulty in constructing sophisticated micro/nano architectures for robust, adhesive superhydrophobic surfaces, especially on fabrics. Here, we present a bioinspired interfacial engineering methodology of “artificial papillae + glue” which allows the construction of tunable multiscale micro/nano structures for superhydrophobic fabrics with mechanical robustness (mechanical friction up to 100 cycles) and varying adhesion (69.4–216.5 µN). For our methodology, artificial papillae with tunable 3D topological architectures, fluorinated alky chains, and hydrosilylation-reactive C = C groups, are designed and synthesized as the robust anchoring groups to different concentrations of polydimethylsioxane (PDMS) glue and applied to hydrophilic substrates. The PDMS-dominated surfaces form microwrinkles with high adhesion, ideal for microdroplet manipulation and hemostasis, meanwhile artificial papillae-dominated surfaces offer low adhesion and excellent self-cleaning properties. This biomimetic “artificial papillae + glue” strategy enables the creation of tunable multi-scale micro/nanostructures for robust adhesive antiwetting interfaces, offering promising applications in droplet manipulation, hemostasis, and beyond.

A tissue-adhesive, mechanically enhanced, natural Aloe Vera-based injectable hydrogel for wound healing: Macrophage mediation and collagen proliferation

Macromolecule hydrogels made from natural extracts have received much attention because of their favorable biocompatibility and wound healing properties. However, their clinical applications are limited by their insufficient mechanical strength and low adhesion properties. To overcome these limitations, we developed a novel injectable Aloe vera hydrogel (PDMA-GelMA@AV). By integrating gelatin methacrylate (GelMA) and polydopamine methacrylamide (PDMA), we significantly improved the mechanical and adhesion properties of the hydrogel. The PDMA-GelMA@AV hydrogel degraded in a simulated wound environment, which was synchronized with the sustained release of the bioactive components of A. vera. In vitro and in vivo analyses revealed that this hydrogel has good biocompatibility. In vitro studies also revealed that the sustained release of the active ingredients of A. vera promoted fibroblast proliferation and migration and increased the expression of key proteins and mRNAs required for wound healing. In addition, it modulated LPS-stimulated macrophages and decreased the expression of TNF-α, IL-1β and iNOS while increasing the expression of TGF-β and ARG. In vivo experiments further confirmed the efficacy of hydrogels in wound healing applications. These findings offer a novel perspective on the application of natural macromolecules as hydrogel-based delivery vehicles in wound care.

The tribological behavior of Cu-based brake materials against Cr3C2-NiCr coated steel disks with varying roughness

A high coefficient of friction (COF) and low wear rate are expected in the braking system for high-speed trains. For this purpose, we prepared coated steel disks by spraying Cr3C2-NiCr powders and slid them against Cu-based powder metallurgy pins. Pin-on-disk tests showed a significant increase in the COF with the Cr3C2-NiCr coated disk (roughness of 1.0 µm) reaching 0.514, compared to 0.366 for the uncoated steel disk. Additionally, there was a notable reduction in wear loss of the brake material, with the coated disk losing only 0.0088g, while the uncoated disk lost 0.0760g.The lower adhesion between the coating and the pin material, combined with the abrasive action of the harder coating on the disk surface, helps maintain the friction surface flat and virgin, thus avoiding the formation of thick friction films and fatigue cracks. As a result, a higher and more stable COF with lower wear was achieved when the coated disk slid against the pins.

A nonlinear optimisation considering axle load transfer for enhancing adhesion utilisation of a locomotive with an oblique traction rod

A nonlinear optimisation considering axle load transfer for enhancing adhesion utilisation of a locomotive with an oblique traction rod

Biomimetic Microstructure with Anti-Slip and Anti-Adhesion for Efficient Handling of Brittle Material Surfaces in High-Temperature Environments.

Non-destructive handling such as wafer handling usually requires a high-temperature environment, however, most bionic materials fail in high temperatures due to material decomposition. In this study, inspired by the unique microstructure of locust toe pads with low adhesion and high friction, bionic high-temperature friction pads are designed and fabricated, selecting high-temperature-resistant silicone rubber as the material. The interfacial mechanical properties at high temperatures are analyzed. The samples with terminal bulges possess preferable roughness adaptability, enabling the advantages of low adhesion and high friction in high temperatures. The high-temperature non-destructive handling experiment using a robotic arm verifies the feasibility of bionic high-temperature friction pads in industrial applications and provides a valuable solution for non-destructive handling in high-temperature environments.

In situ synthesis of Fe3O4/ carboxylated multi-walled carbon nanotubes nanostructures on nylon fabric with efficient flame retardant and antibacterial properties

Knitted fabrics are ideal for flexible, conductive, and magnetic smart textiles but have low adhesion for materials, especially inorganic ones. In this study, carboxylated multi-walled carbon nanotubes (MWCNT-COOH) and magnetite (Fe3O4) magnetic nanoparticles were synthesized in situ and then coated onto nylon knitted fabric. Using nylon and in situ coating of these nanostructures enhances nanotube absorption via hydrogen bonding and provides magnetite growth sites on both the coated nanotubes and the fabric surface, due to the direct attraction of positively charged iron salts to the polar bonds of nylon. The effect of the weight ratio on the characteristics was evaluated through the coatings with Fe3O4 to MWCNT-COOH at different ratios. Surface structure, chemical analysis, microstructure, electrical conductivity, magnetic properties, antibacterial properties, zeta potential, and thermal properties were studied. FESEM results and surface structure evaluation indicated that increasing the quantity of iron salts influenced the morphology: a single layer was observed at a 2:1 ratio and the combination of layers and particles at 4:1 and 6:1 ratios. At 8:1, there was a recurrence of a layered structure. Magnetite nanoparticles led to the fusion of carbon nanotubes and this was evident from the magnetic characteristic of the fabric. Magnetic properties showed an increasing trend up to the 6:1 ratio (from 0.06 emu/g to 1.00 emu/g) and then decreased at the 8:1 ratio (0.71 emu/g) due to an increase in the number of agglomerations in the solution. These observations were further supported by crystallography analysis of the synthesized magnetite nanoparticles which showed variations in the crystal size. The fabric had better adhesion of carbon nanotubes with increased iron salt content which helped in coating and conductivity. The introduction of these nanostructures also greatly enhanced the heat-resistant properties of the fabrics with the burning length reduced by about 70 % while the photothermal properties of the fabrics reached 81°C. In addition, a significant antibacterial effect was observed in the present study with a minimum of 64 % efficiency under non-irradiated conditions and up to 99 % bacterial killing under irradiated conditions.

Surfactants can compete with microplastics for surfaces using adhesives as substrates for microplastic sequestration

Experimental efforts supplemented by modeling gauged whether common additives found in soaps and laundry detergents interfered with polyacrylate adhesive-based capture of microplastics. On the experimental front, poly(2-ethylhexyl acrylate) (PEHA) samples were evaluated using gravimetric analysis, probe tack, and functional assessments of adhesive-coated glass slides immersed into DI water solutions containing both microparticles and additives (solvents, softeners, and non-ionic surfactants). Nylon-6 spheres and polyethylene terephthalate microplastics were chosen for adsorption using a count-based method by ImageJ imaging analysis. Molecular dynamics computations simulated 2-ethyl-hexylacrylate (2-EHA) adhesive and microplastic interactions in the presence of water, citrate, glycerol and tergitol detergent additives. The experimental work showed that fewer microplastics were collected when tergitol was added and was in line with lower experimental Work of Adhesion (WoAaq) results for nylon and PETE (94.5% and 54.5% reductions respectively). Computational results also confirmed lower adhesion in the presence of tergitol. The experiments also showed that the adhesive swelled while equilibrating in additive solutions. Models suggested that tergitol most negatively impacted particle binding through a competitive “blocking” of the adhesive substrate while the other additives were less conclusive about potential interferences based on competitive binding.

Sticky Superhydrophobic State.

It is common sense that the droplet is stickier to substrates with larger solid-liquid contact areas. Here, we report that this intuitive trend reverses for hollowed micropillars, where a decrease in solid-liquid contact area caused by an increase in the pore size of a pillar top leads to an increase in the droplet depinning force. As compared to relief of liquid-vapor interface distortion caused by the sliding of the contact line on filled pillars, the pore hinders the contact line sliding, hence leading to enhanced interface distortion and droplet adhesion. The droplet on hollowed micropillars is completely suspended above the vapor but inherently sticky. Hence, this counterintuitive phenomenon is termed as the sticky superhydrophobic state in contrast to the conventional superhydrophobic state with low adhesion. A model building upon the dynamics of the contact line and liquid-vapor interface, which successfully predicts the droplet depinning force on filled and hollowed pillars, is introduced.

Preparation and characterization of sago/iota-carrageenan microgels as food thickener in texture modified food

An increasing number of older populations with swallowing difficulties need specialized diets with easy-to-chew and safe swallowing characteristics. Texture modification using a thickener is usually used to obtain the desired texture, which helps in lowering the risk of aspiration. Microgels usage to modify the texture and rheology of liquid and pureed foods has been an area of interest in the food industry for many years. Therefore, this study aimed to produce sago starch and ι-carrageenan based microgels with functionality as food thickeners. Different concentrations of ι-carrageenan (25%, 50% and 75%) were added into sago starch dispersion and then fabricated using ultrasound treatment followed by spray drying process. A commercial dysphagia thickener that is normally used at medical institutions and nursing homes was also included as a reference. Microgels with increasing ι-carrageenan concentration showed variation in behaviours during rheological and textural measurements. Rheological tests revealed that sago/ι-carrageenan microgels exhibited a predominant elastic behaviour, with G′>G″ within the frequency range. Texture profile analysis (TPA) suggested that the sample with 2.0 g of sago starch and 2.0 g ι-carrageenan, MS50, produced samples with similar hardness, springiness, and cohesiveness to the reference sample. Overall, sago/ι-carrageenan microgels have shown a potential to be used as an alternative thickener as it provides low adhesiveness and more elastic behaviour which is considered safe-to-swallow food, especially for elderly with swallowing difficulties.

Magnetically responsive superhydrophobic surface: Reversible switching for water repellency and active/passive anti-icing

This research aims to address the negative impact of global climate change on equipment stability, with a particular focus on the occurrence of icing on working surfaces at low temperature. To this end, we have developed a novel magnetically responsive superhydrophobic surface to enhance anti-icing properties and adapt to environmental changes. We prepared magnetically responsive micro-cilia arrays (MRMAs) with good flexibility and magnetostriction through a facile spray gun coating technique. By adjusting the application mode and distance of the magnetic field, three different morphologies can be achieved: vertical, curved and crossed, thus optimizing water repellency, active anti-icing and passive anti-icing performance. Experimental data show that vertical MRMAs exhibit extremely high contact angles and low droplet adhesion, which facilitates rapid water droplet removal, while curved MRMAs exhibit the lowest ice adhesion strength, which effectively reduces the likelihood of ice formation. In addition, the crossed MRMAs excelled in delaying icing, significantly prolonging the time before water droplets begin to freeze. This research not only provides a novel anti-icing strategy, but also offers new ideas for designing multifunctional surfaces that can adapt to complex environmental conditions.

Construction of Iron-Modified Lignin-Based Nanomicrocapsules for Enhancing the Functionality of Natural Product-Based Pesticides.

To address the issue of low pesticide utilization owing to poor dispersibility, low leaf surface adhesion, and poor transport within plants, this study exploits electrostatic interactions between sodium lignosulfonate (SL) and dodecyltrimethylammonium chloride (DTAC) to induce self-assembly, followed by iron ion (Fe3+) chelation and loading with a natural product-based pesticide, rosin-based triazole derivative (RTD), yielding RTD@SL-DTAC-Fe nanomicrocapsules (NMs). It is worth noting that the presence of Fe3+ enhances the dispersibility of the NMs. The water dispersibility and photostability of RTD are significantly improved after encapsulation, and a stimulus response to laccase is achieved. Leaf-washing experiments confirm the enhanced adhesion of RTD@SL-DTAC-Fe NMs to the surface of rice plant leaves compared to that of free RTD. Fluorescently labeled NMs exhibit bidirectional transport within rice plants, and RTD@SL-DTAC-Fe NMs demonstrates better transport performance than RTD. In vitro and in vivo antifungal tests indicate that encapsulation by NMs significantly enhanced pesticide activity. Field trials demonstrate that NMs exhibited prolonged efficacy compared to RTD. Finally, the safety evaluation confirms the environmental friendliness of the NMs. This study provides valuable insight for optimizing and improving the utilization efficiency and biosafety of natural product-based pesticides.

Superhydrophobicity With Self-Adaptive Water Pressure Resistance and Adhesion of Pistia Stratiotes Leaf.

Superhydrophobic surfaces are promising for optimizing amphibious aircraft by minimizing water drag and adhesion. Achieving this involves ensuring these surfaces can resist high liquid pressure caused by deep water and fluid flow. Maximizing the solid-liquid contact area is a common strategy to improve liquid pressure resistance. However, this approach inevitably increases solid-liquid adhesion, making it challenging to guarantee a trade-off between the two wetting characteristics. Here, it is found that the Pistia stratiotes leaf exhibits superhydrophobicity with high water pressure resistance and low adhesion, attributed to its self-adaptive deformable microstructure with unique re-entrant features. Under pressure, these microstructures deform to increase the solid-liquid contact area, thereby enhancing water pressure resistance. The re-entrant features elevate the deformation threshold, enabling higher modulus microstructures to achieve adaptive response. This facilitates the recovery of deformed microstructures, restoring the air layer and maintaining low adhesion. Following these concepts, Pistia stratiotes leaf-inspired surfaces are fabricated, achieving an 183% improvement in water impact resistance and an ≈80% reduction in adhesion after overpressure compared to conventional superhydrophobic surfaces. The design principles inspired by Pistia stratiotes promise significant advancements in amphibious aircraft and other trans-media vehicles.

Mechanochemical Damage Self‐Repairable Photothermal Anti/De‐Icing Superhydrophobic Coating by Dynamic Bonding Phase‐Change Fillers with the Matrix

AbstractThe development of robust superhydrophobic coatings with the capacity for self‐healing against mechanochemical damage is pivotal for their practical deployment. This study develops a physically and chemically self‐healing superhydrophobic coating with exceptional durability for anti‐icing applications using a simple spray coating method. This is achieved by incorporating phase‐change fillers into a dynamic cross‐linked matrix via dynamic imine bonds. Specifically, oleylamine (ODA) is encapsulated within rigid diatomite nanopores and modified with dopamine (DOA), significantly enhancing the grafting efficiency of aminopropyl‐terminated polydimethylsiloxane (NH₂‐PDMS‐NH₂) (N‐DOA). The incorporation of 15% N‐DOA increases the water contact angle (WCA) of the acrylic resin/aminopropyl‐terminated polydimethylsiloxane (AR/NH₂‐PDMS‐NH₂) matrix to 159.7° and reduces the sliding angle (SA) to 2.9°, while also improving the mechanical durability of coating to withstand 600 abrasion cycles. The dynamic imine bonds between NH₂‐PDMS‐NH₂ and trimesic acid (BTC) facilitate the mobility of N‐DOA and NH₂‐PDMS‐NH₂, enabling rapid recovery of superhydrophobic properties and low ice adhesion strength after abrasions, scratches, oxygen plasma etching, and multiple de‐icing cycles due to the synergistic phase‐change effect of ODA. Thus, the self‐healing coating produced via this simple spray method presents a novel approach for superhydrophobic coatings in anti‐icing applications.

Evaluation of Mixing Temperature in the Preparation of Plant-Based Bigels.

Understanding gel structures and behavior is a prerequisite for attaining the desired food application characteristics. The mixing temperature is crucial when incorporating thermolabile active compounds into gels. This study evaluated the effect of mixing temperature on the physical and chemical properties of a bigel system prepared using a carnauba wax/canola oil oleogel and Arabic gum hydrogels. The results showed that bigels prepared at lower temperatures (30 and 40 °C) resulted in a solid-like state under crystallization temperature, resulting in matrices with larger hydrogel droplets, softer texture, and lower adhesiveness, spreadability, and solvent binding capacity. In contrast, bigels prepared at higher temperatures (50 and 60 °C), around crystallization temperature but with no solid state, resulted in matrices with smaller hydrogel droplets and higher firmness, adhesiveness, and spreadability. These bigels had a higher apparent viscosity, especially at lower shear rates, and solid-like behavior in the linear viscosity range. During the bigel preparation process, adjusting the mixture temperature had no effect on the samples' oxidative stability, FTIR spectra, or thermal properties. The results highlighted the importance of hydrogel droplet size on the microstructure of the formed bigels, and smaller droplets could act as effective fillers to reinforce the matrix without making chemical changes.