High Adhesive Force Research Articles

Effect of Chemical Surface Treatment on Flax-Reinforced Epoxy Composite

ABSTRACTThe aim of this study is to examine the impact of surface modification on properties of flax fiber and flax-reinforced composites. For this purpose, acetic anhydride, sodium hydroxide, and silane were used to treat surface of the flax fiber. The effects of treatments on fiber were investigated by using contact angle, attenuated total reflectance-Fourier transform infrared, atomic force microscopy (AFM), and scanning electron microscopy (SEM). Contact angle and AFM results revealed that sodium hydroxide-treated flax fibers have higher adhesion force on the fiber surface. Particularly, NaOH treatment improved the mechanical properties of the epoxy matrix composite.

Adhesion and friction forces in biofouling attachments to nanotube- and PEG- patterned TiO2 surfaces

The TiO2 nanotube pattern with features down to 20nm (TN20) is highly and efficiently resistant to fibrinogen and S. aureus attachment. The ability of TN20 to resist biofouling adsorption, is due to low biofouling-surface adhesion force that determines the initial biofouling attachment, as well as the low friction coefficient that enables a complete removal of biofouling from a low-adhesive ‘repelling’ TN20 substrate under fluid flow. By grafting PEG molecules onto TN20, a significantly higher S. aureus cells attachment was observed, because of the stronger adhesion forces originated from the deformation of the soft PEG coatings. The complete interaction of S. aureus on structure-free dense TiO2 (DT), yields larger contact area and thus higher adhesion force than on any other TiO2 surfaces, resulting in a high coverage of bacteria. The existing high friction coefficient of S. aureus on TN80 (TiO2 with 80nm nanotubular size) and TN80-P (PEG-modified TN80), due to the much greater surface roughness, would contribute to the immobilization of biofouling on the surface under fluid flow, even though the two surfaces exhibit low adhesion forces. The analysis of adhesion and friction forces manipulated by TiO2 nanotubular topography and posted PEG patterns, advances our understanding of the mechanisms by which nanotopography patterned surfaces reduce biofouling attachment.

Effect of absorbed water on the adhesion, friction, and wear of phosphate laser glass at nanoscale

AbstractThe interaction between glass and micro‐particle in the presence of absorbed water could affect glass surface integrity, especially for the phosphate glass with a poor water resistance. In this work, using an atomic force microscope equipped with an environment chamber, the adhesion, friction and wear behaviors of phosphate laser (PL) glass were investigated by contacting with an SiO2 microsphere under vacuum, dry air, and humid air, respectively, to reveal the effect of the absorbed water on the interactions between glass and particle. Compared to vacuum and dry air, a higher adhesion force and friction coefficient as well as more material removal of PL glass were found in humid air. The capillary force caused by absorbed water greatly contributes to the high adhesion and friction in humid air. Moreover, the water meniscus forming at glass‐particle interface provides an environment for hydrolyzing P–O–P network and assists the material removal of PL glass under shear stress. Comparing the results after rubbing the SiO2 particle to those rubbed by the CeO2 particle in our previous work, in humid air, a higher shear stress and material removal rate were found in PL glass‐CeO2 pair than in the PL glass‐SiO2 pair, indicating that in the presence of absorbed water, countersurface chemistry also plays an important role in the friction and wear of PL glass at the nanoscale surface.

A Facile All-Solution-Processed Surface with High Water Contact Angle and High Water Adhesive Force.

A series of sticky superhydrophobicity surfaces with high water contact angle and high water adhesive force is facilely prepared via an all-solution-processed method based on polymerization-induced phase separation between liquid crystals (LCs) and epoxy resin, which produces layers of epoxy microspheres (EMSs) with nanofolds on the surface of a substrate. The morphologies and size distributions of EMSs are confirmed by scanning electron microscopy. Results reveal that the obtained EMS coated-surface exhibits high apparent contact angle of 152.0° and high water adhesive force up to 117.6 μN. By varying the composition of the sample or preparing conditions, the sizes of the produced EMSs can be artificially regulated and, thus, control the wetting properties and water adhesive behaviors. Also, the sticky superhydrophobic surface exhibits excellent chemical stability, as well as long-term durability. Water droplet transportation experiments further prove that the as-made surface can be effectively used as a mechanical hand for water transportation applications. Based on this, it is believed that the simple method proposed in this paper will pave a new way for producing a sticky superhydrophobic surface and obtain a wide range of use.

Friction and wear of hydrogenated and hydrogen-free diamond-like carbon films: Relative humidity dependent character

In this study, tribological properties of hydrogenated and hydrogen free diamond-like carbon films at various relative humidity (RH) were investigated to understand the friction mechanism in the presence of water molecules. At normal load of 2N, DLC-H film’s friction coefficient was 0.06 at RH14% while DLC film’s friction coefficient was 0.19 at RH17%. With the increase of RH, their friction coefficient converged to about 0.15. This character remained unaltered when the normal load was 5N. Results show that low friction of DLC-H film at low RH was attributed to the low shear force aroused by graphitic tribofilm at wear care center. However, the high friction of DLC film was mainly endowed by the high adhesive force aroused by σ dangling bonds. At high RH, solid-to-solid contact was isolated by water molecules confined between the counterfaces, where capillary was a dominant factor for friction. In addition to the capillary force, the absence of tribofilm was also accountable. These two factors lead to the level off of friction coefficient for DLC-H and DLC films. Moreover, for both DLC-H and DLC films, tribo-oxidization was proved to be closely related to wear rate with the assist of H2O molecules during sliding.

Evaluation of polyvinyl alcohols as mucoadhesive polymers for mucoadhesive buccal tablets prepared by direct compression

The purpose of the present work was to evaluate polyvinyl alcohols (PVAs) as a mucoadhesive polymer for mucoadhesive buccal tablets prepared by direct compression. Various polymerization degree and particle diameter PVAs were investigated for their usability. The tensile strength, in vitro adhesive force, and water absorption properties of the tablets were determined to compare the various PVAs. The highest values of the tensile strength and the in vitro adhesive force were observed for PVAs with a medium viscosity and small particle size. The optimal PVA was identified by a factorial design analysis. Mucoadhesive tablets containing the optimal PVA were compared with carboxyvinyl polymer and hydroxypropyl cellulose formulations. The optimal PVA gives a high adhesive force, has a low viscosity, and resulted in relatively rapid drug release. Formulations containing carboxyvinyl polymer had high tensile strengths but short disintegration times. Higher hydroxypropyl cellulose concentration formulations had good adhesion forces and very long disintegration times. We identified the optimal characteristics of PVA, and the usefulness of mucoadhesive buccal tablets containing this PVA was suggested from their formulation properties.

Influence of Humidity on Grip and Release Adhesion Mechanisms for Gecko-Inspired Microfibrillar Surfaces.

Geckos have developed foot pads that allow them to maintain their unique climbing ability despite vast differences of surfaces and environments, from dry desert to humid rainforest. Likewise, successful gecko-inspired mimics should exhibit adhesive and frictional performance across a similarly diverse range of climates. In this work, we focus on the effect of relative humidity (RH) on the "frictional-adhesion" behavior of gecko-inspired adhesive pads. A surface forces apparatus was used to quantitatively measure adhesion and friction forces of a microfibrillar cross-linked polydimethylsiloxane surface against a smooth hemispherical glass disk at varying relative humidity, from 0 to 100% (including fully submerged under water). Geometrically anisotropic tilted half-cylinder microfibers yield a "grip state" (high adhesion and friction forces after shearing along the tilt of the fibers, Fad+ and F∥+) and a "release state" (low adhesion and friction after shearing against the tilt of the fibers, Fad- and F∥-). By appropriate control of the loading path, this allows for transition between strong attachment and easy detachment. Changing the preload and shear direction gives rise to differences in the effective contact area at each fiber and the microscale and nanoscale structure of the contact while changing the relative humidity results in differences in the relative contributions of van der Waals and capillary forces. In combination, both effects lead to interesting trends in the adhesion and friction forces. At up to 75% RH, the grip state adhesion force remains constant and the ratio of grip to release adhesion force does not drop below 4.0. In addition, the friction forces F∥+ and F∥- and the release state adhesion force Fad- exhibit a maximum at intermediate relative humidity between 40% and 75%.

Graphene Oxide Glue-Electrode for Fabrication of Vertical, Elastic, Conductive Columns.

Graphene has a planar atomic structure with high flexibility and might be used as ultrathin conductive glues or adhesion layers in electronics and other applications. Here, we show that graphene oxide (GO) sheets condensed from solution can act as a pure, thin-layer, nonpenetrating glue for fabrication of vertical architectures anchored on rigid and flexible substrates. Carbon nanotube (CNT) sponges are used as a porous template to make polymer-reinforced composite columns, to achieve both high conductivity and elastic behavior. These vertical columns are fixed on a substrate by reduced GO sheets as an electrode and exhibit reversible resistance change under large-strain compression for many cycles. Similar to the CNT gecko feet, we disclose high adhesion forces at the CNT-GO and GO-SiO2 interfaces by mechanical tests and theoretical calculation. Three-dimensional CNT, graphene, and nanowire networks with our GO glue-electrodes have potential applications as energy storage electrodes, flexible sensors, functional composites, and vertical interconnects.

Adhesion of ligand-conjugated biosynthesized magnetite nanoparticles to triple negative breast cancer cells

This paper presents the results of an experimental study of the adhesion forces between components of model conjugated magnetite nanoparticle systems for improved selectivity in the specific targeting of triple negative breast cancer. Adhesion forces between chemically synthesized magnetite nanoparticles (CMNPs), biosynthesized magnetite nanoparticles (BMNPs), as well as their conjugated systems and triple negative breast cancer cells (MDA-MB-231) or normal breast cells (MCF 10A) are elucidated at a nanoscale. In all cases, the BMNPs had higher adhesion forces (to breast cancer cells and normal breast cells) than CMNPs. The adhesion of LHRH-conjugated BMNPs or BSA-conjugated BMNPs to cancer cells is shown to be about 6 times to that of normal breast cells. The increase in adhesion forces between luteinizing hormone-releasing hormone, LHRH- or EphA2, a breast specific antibody(BSA)-conjugated BMNPs to breast cancer cells is attributed to van der Waals interactions between the peptides/antibodies from the conjugated nanoparticles and the over-expressed receptors (revealed using immunofluorescence staining) on the surfaces of the breast cancer. The implications of the results are discussed for the selectivity and specificity of breast cancer targeting by ligand-conjugated BMNPs.

Effect of kaolinite and montmorillonite on fine coal flotation

The effect of kaolinite and montmorillonite on fine coal flotation in deionized water and calcium solution were studied through flotation experiments on a mixed coal–kaolinite/montmorillonite system in the present study, respectively. Fuerstenau upgrading curve was used to evaluate the whole flotation selectivity and the interaction force between kaolinite/montmorillonite and coal was measured using atomic force microscopy (AFM) colloidal probe technique. It was found that kaolinite and montmorillonite caused different issues in coal flotation process. In deionized water, the results show that a lower flotation recovery and worse selectivity were obtained for coal-montmorillonite system compared with that of coal-kaolinite. AFM results show that slightly jump-into-contact phenomenon was observed in coal–montmorillonite interaction while a repulsive force was always detected in coal–kaolinite interaction. The heterocoagulation between coal and montmorillonite was responsible for the low flotation recovery and bad selectivity in deionized water for coal-montmorillonite system. In presence of 0.1mol/L calcium ion, the flotation recovery increased considerably while the selectivity of both systems was deteriorated. The jump-into-contact and high adhesion force were always found in coal-kaolinite/montmorillonite AFM force curves, indicating attractive force dominated the interaction between kaolinite/montmorillonite and coal. The electrostatic repulsive force between coal and clay particle or air bubble is fully suppressed by Ca2+, aggravating the kaolinite/montmorillonite coating and also leading to an increase of flotation recovery.

Investigation of the adhesion properties of direct 3D printing of polymers and nanocomposites on textiles: Effect of FDM printing process parameters

In this paper, 3D printing as a novel printing process was considered for deposition of polymers on synthetic fabrics to introduce more flexible, resource-efficient and cost effective textile functionalization processes than conventional printing process like screen and inkjet printing. The aim is to develop an integrated or tailored production process for smart and functional textiles which avoid unnecessary use of water, energy, chemicals and minimize the waste to improve ecological footprint and productivity. Adhesion of polymer and nanocomposite layers which were 3D printed directly onto the textile fabrics using fused deposition modeling (FDM) technique was investigated. Different variables which may affect the adhesion properties including 3D printing process parameters, fabric type and filler type incorporated in polymer were considered. A rectangular shape according to the peeling standard was designed as 3D computer-aided design (CAD) to find out the effect of the different variables. The polymers were printed in different series of experimental design: nylon on polyamide 66 (PA66) fabrics, polylactic acid (PLA) on PA66 fabric, PLA on PLA fabric, and finally nanosize carbon black/PLA (CB/PLA) and multi-wall carbon nanotubes/PLA (CNT/PLA) nanocomposites on PLA fabrics. The adhesion forces were quantified using the innovative sample preparing method combining with the peeling standard method. Results showed that different variables of 3D printing process like extruder temperature, platform temperature and printing speed can have significant effect on adhesion force of polymers to fabrics while direct 3D printing. A model was proposed specifically for deposition of a commercial 3D printer Nylon filament on PA66 fabrics. In the following, among the printed polymers, PLA and its composites had high adhesion force to PLA fabrics.

Robust superhydrophobic diamond microspheres for no-loss transport of corrosive liquid microdroplets.

Superhydrophobic surfaces usually lose their characteristics when exposed to a corrosive environment. To solve this issue, we synthesized superhydrophobic diamond microspheres by microwave-plasma-assisted chemical vapor deposition. Commercial epoxy glue was used to bond the microspheres to various substrates. The thus-synthesized composite films exhibited robust superhydrophobicity and an ultrahigh adhesive force.

タコの吸盤の漏斗形状と表面の微細な溝を模倣した真空吸着グリッパの開発

An octopus suction cup has the characteristic structures, for example a narrow part on sidewall and cone-shaped bottom with radial and cylindrical trenches. These structures will have the function of enhancing flexibility of suction cup. In this paper, we evaluated the effect of three structures imitating octopus suction cup on gripping performance by Finite Element Method (FEM) simulation and the fabricated 8 types of gripper. The narrow part on sidewall and cone-shaped bottom enhanced the followability to a shape. On the other hand, the radial trenches on bottom reduced the ability. The gripper with these structure generated same or higher adhesive force than one without structures.

Design and engineering of sculptured nano-structures for application in hydrophobicity

Abstract The design and engineering of suitable structures for enhancement of the hydrophobic property of a surface is one of the most challenging problems. In order to achieve a superhydrophobic structure we have designed and fabricated Mn nano-sculptured thin films with different shapes and dimensions, namely helical squares and helical pentagons on glass substrates. The contact angle (CA) of three liquids; α–bromonaphtalene (apolar), water and formamide (polar) to these surfaces was measured and the surface free energy was calculated. Changes to the geometry of the structure produced results ranging from hydrophilic (CA = 51°) to superhydrophobic (CA = 152°). The superhydrophobic structure is a helical square shaped structure with high porosity (deposited at 83°) which also shows the rose petal effect with the additional property of high adhesion. The resemblance of this structure to that of gecko feet, which shows both high adhesion forces and superhydrophobic property is discussed. All structures investigated in this work showed negative spreading coefficients with highest values for the largest contact angle for each type/shape of structure. The superhydrophobic sample also acts as a sticky surface which is confirmed by hysteresis of the contact angle obtained from advancing and receding contact angles measurements. The influence of the volume of liquid drop and different surface morphologies on the wetting transition from Cassie–Baxter to Wenzel states is also reported.

New denture adhesive containing miconazole nitrate polymeric microparticles: Antifungal, adhesive force and toxicity properties

ObjectiveThe purpose of this study was to develop a new oral drug delivery system by incorporating polymeric miconazole nitrate (MN) microparticles on an experimental antifungal denture adhesive (DA). MethodsSpray drying Eudragit L-100 (E) and Gantrez MS-955 (G) MN-microparticles were incorporated in DA. DAE1, DAG1, DAEG1, DAE2, DAG2, DAEG2 groups were obtained from the combination of polymers used in MN-microparticles (E, G and EG) and concentration of MN into DA (1, for 1% and 2, for 2%). DA with 2% pure MN (DAM) and DA without microparticles or drug (DACT) were both control groups. All groups were evaluated to determine microbiological assay, adhesive force and toxicity. Minimum inhibitory concentration (MIC) against Candida albicans was performed by broth micro-dilution and agar dilution methods in extract of DAs and conventional gel form (Daktarin®). Adhesive load testing was made between acrylic resin samples on a universal testing machine after immersion in water. The toxicity of several dilutions of DAs was performed with Artemia salina bioassay after 24 and 48h. Data of adhesive force were evaluated with two-way ANOVA and Bonferroni tests (α=0.05). ResultsThe concentration required to kill 50% (LC50) was determined using the Provit analysis. DA with polymeric microparticles and pure drug presented MIC between 1.25–5μg/mL similar to MIC values of DAM. DAEG2, DAEG1, DAG20 showed the most actives against C. albicans. The best adhesive properties were exhibited by DAEG2, consisting of high initial adhesive force which was maintained for up to 6h. The extracts of all DA presented low or not toxicity at 24 and 48h. SignificanceDA containing 2% of MN loaded in microparticles made by Gantrez MS-955 alone or combined with Eudragit L-100 produce effective antifungal activity, good adhesive force, and no toxicity effect being a promising therapeutics for removable denture wearers affected by denture stomatitis.

Developments for Physical Cleaning Sample with High Adhesion Force Particles and Direct Measurement of its Removal Force

We quantitatively evaluate the wet cleaning performance of particle cotamination. We made particle sample which endure the wet cleaning and measured particle adhesion force by self-sensitive cantilever. The advantage of this method is that performed in both air and water. As a result, there were no significant differences between the air and water condition and the influence of particle size were dominant. Using this sample, we demonstrated particle removal rate of droplets impacts and PVA brush.

A facile and cost-effective approach to engineer surface roughness for preparation of large-scale superhydrophobic substrate with high adhesive force

This study presents a convenient avenue to fabricate polydimethylsiloxane (PDMS) with controllable surface morphologies and wetting characteristics via standard molding technique. The templates with engineered surface roughness were simply prepared by combinations of microfluidics and photo-polymerization of N-Isopropylacrylamide (NIPAM). The surface morphology of mold could be adjusted via ultraviolet-curing duration or the grafting density, which means that the surface of PDMS sample replicated from the mold could also be easily controlled based on the proposed method. Furthermore, via multiple grafting and replication processes, we have successfully demonstrated that hydrophobicity properties of prepared PDMS samples could be swiftly enhanced to ∼154° with highly adhesive force with resident water droplets. The obtained PDMS samples exhibited well resistance to external mechanical deformation even up to 100 cycles. The proposed scheme is timesaving, cost-effective and suitable for large-scale production of superhydrophobic PDMS substrates. We believe that the presented approach can provide a promising method for preparing superhydrophobic surface with highly adhesive force for on-chip liquid transport, localized reaction, etc.

Elasto-capillarity in insect fibrillar adhesion.

The manipulation of microscopic objects is challenging because of high adhesion forces, which render macroscopic gripping strategies unsuitable. Adhesive footpads of climbing insects could reveal principles relevant for micro-grippers, as they are able to attach and detach rapidly during locomotion. However, the underlying mechanisms are still not fully understood. In this work, we characterize the geometry and contact formation of the adhesive setae of dock beetles (Gastrophysa viridula) by interference reflection microscopy. We compare our experimental results to the model of an elastic beam loaded with capillary forces. Fitting the model to experimental data yielded not only estimates for seta adhesion and compliance in agreement with previous direct measurements, but also previously unknown parameters such as the volume of the fluid meniscus and the bending stiffness of the tip. In addition to confirming the primary role of surface tension for insect adhesion, our investigation reveals marked differences in geometry and compliance between the three main kinds of seta tips in leaf beetles.

Breast cancer cells compete with hematopoietic stem and progenitor cells for intercellular adhesion molecule 1-mediated binding to the bone marrow microenvironment.

Adhesion-based cellular interactions involved in breast cancer metastasis to the bone marrow remain elusive. We identified that breast cancer cells directly compete with hematopoietic stem and progenitor cells (HSPCs) for retention in the bone marrow microenvironment. To this end, we established two models of competitive cell adhesion-simultaneous and sequential-to study a potential competition for homing to the niche and displacement of the endogenous HSPCs upon invasion by tumor cells. In both models, breast cancer cells but not non-tumorigenic cells competitively reduced adhesion of HSPCs to bone marrow-derived mesenchymal stromal cells (MSCs) in a tumor cell number-dependent manner. Higher adhesive force between breast cancer cells and MSCs, as compared with HSPCs, assessed by quantitative atomic force microscopy-based single-cell force spectroscopy could partially account for tumor cell mediated reduction in HSPC adhesion to MSCs. Genetic inactivation and blockade studies revealed that homophilic interactions between intercellular adhesion molecule 1 (ICAM-1) expressed on tumor cells and MSCs, respectively, regulate the competition between tumor cells and HSPCs for binding to MSCs. Moreover, tumor cell-secreted soluble ICAM-1(sICAM-1) also impaired HSPC adhesion via blocking CD18-ICAM-1 binding between HSPCs and MSCs. Xenotransplantation studies in NOD.Cg-Prkdc(scid) Il2rg(tm1Wjl)/SzJ mice revealed reduction of human HSPCs in the bone marrow via metastatic breast cancer cells. These findings point to a direct competitive interaction between disseminated breast cancer cells and HSPCs within the bone marrow micro environment. This interaction might also have implications on niche-based tumor support. Therefore, targeting this cross talk may represent a novel therapeutic strategy.

Physical Characteristics of the Leaves and Latex of Papaya Plants Infected with the Papaya meleira Virus.

Sticky disease, which is caused by Papaya meleira virus (PMeV), is a significant papaya disease in Brazil and Mexico, where it has caused severe economic losses, and it seems to have spread to Central and South America. Studies assessing the pathogen-host interaction at the nano-histological level are needed to better understand the mechanisms that underlie natural resistance. In this study, the topography and mechanical properties of the leaf midribs and latex of healthy and PMeV-infected papaya plants were observed by atomic force microscopy and scanning electron microscopy. Healthy plants displayed a smooth surface with practically no roughness of the leaf midribs and the latex and a higher adhesion force than infected plants. PMeV promotes changes in the leaf midribs and latex, making them more fragile and susceptible to breakage. These changes, which are associated with increased water uptake and internal pressure in laticifers, causes cell disruption that leads to spontaneous exudation of the latex and facilitates the spread of PMeV to other laticifers. These results provide new insights into the papaya-PMeV interaction that could be helpful for controlling papaya sticky disease.