Mechanical Rubbing Research Articles

Anodic dissolution dictates the negative difference effect (NDE) of magnesium corrosion more in chemical pathway

The driving force of hydrogen evolution (HE) on Mg anode was investigated by continuously enlarging the exposed area of fresh Mg via mechanical rubbing and chemical attack during anodic polarization. The data show that release of hydrogen on Mg anode was mainly associated with exposed Mg. Meanwhile, the differences in anodic HE behaviors obtained with two exposure methods indicate that hydrogen was predominantly generated via chemical reaction between Mg and electrolyte on Mg anode surface.

The Influence of Mechanical Rubbing on the Dissolution of Blood Clots.

Mechanical rubbing of blood clots is a potential minimally-invasive method for clearing clogged blood vessels. In this work, we investigate the influence of the interaction of the tip of a helical robot with blood clots. This interaction enables the dissolution of the blood clot and the release of the entrapped red blood cells and platelets from its three-dimensional fibrin fiber network. We analyze the pre- and post-conditions of the blood clots following 40 minutes of mechanical rubbing, under the influence of a rotating magnetic field in the frequency range of 20 Hz to 45 Hz. Our measurements show that the weight of the blood clots is decreased by 22.5 ± 11.1% at frequency of 25 Hz. We also validate the influence of mechanical rubbing using cell count and spectrophotometric analysis on phosphate buffered saline samples past the robot and the clot. The maximum cell count is measured as 654 ± 108 × 104 cells/m1 and 54 ± 12 × 104 cells/m1, whereas the absorbance is measured as 4. 35 × 10-6 mol and 1. 05 × 10-6 mol under the influence of mechanical rubbing and without mechanical rubbing, respectively.

Molecular Orientation: Simultaneous Edge‐on to Face‐on Reorientation and 1D Alignment of Small π‐Conjugated Molecules Using Room‐Temperature Mechanical Rubbing (Adv. Funct. Mater. 19/2018)

Molecular Orientation: Simultaneous Edge‐on to Face‐on Reorientation and 1D Alignment of Small π‐Conjugated Molecules Using Room‐Temperature Mechanical Rubbing (Adv. Funct. Mater. 19/2018)

Mechanical Rubbing of Blood Clots Using Helical Robots Under Ultrasound Guidance

A simple way to mitigate the potential negative side-effects associated with chemical lysis of a blood clot is to tear its fibrin network via mechanical rubbing using a helical robot. Here, we achieve mechanical rubbing of blood clots under ultrasound guidance and using external magnetic actuation. Position of the helical robot is determined using ultrasound feedback and used to control its motion toward the clot, whereas the volume of the clots is estimated simultaneously using visual feedback. We characterize the shear modulus and ultimate shear strength of the blood clots to predict their removal rate during rubbing. Our in vitro experiments show the ability to move the helical robot controllably toward clots using ultrasound feedback with average and maximum errors of ${\text{0.84}\pm \text{0.41}}$ and 2.15 mm, respectively, and achieve removal rate of $-\text{0.614} \pm \text{0.303}$ mm $^{3}$ /min at room temperature ( ${\text{25}}^{\circ }$ C) and $-\text{0.482} \pm \text{0.23}$ mm $^{3}$ /min at body temperature (37 $^{\circ}$ C), under the influence of two rotating dipole fields at frequency of 35 Hz. We also validate the effectiveness of mechanical rubbing by measuring the number of red blood cells and platelets past the clot. Our measurements show that rubbing achieves cell count of $(\text{46} \pm \text{10.9}) \times \text{10}^{4}$ cell/ml, whereas the count in the absence of rubbing is $(\text{2} \pm \text{1.41}) \times \text{10}^{4}$ cell/ml, after 40 min.

Time-dependent electrical properties of liquid crystal cells: unravelling the origin of ion generation

ABSTRACTAn understanding of possible sources of ion generation in liquid crystal materials is of utmost importance to ensure uncompromised performance of modern liquid crystal devices. In this paper, time-dependent electrical properties of filled liquid crystal cells are used to reveal important information about often overlooked source of ion generation in liquid crystals. This source of ions originates from the ionic contamination of substrates of the liquid crystal cell. Ionic contaminants can be inherently present in the alignment layers or can be induced by external factors such as mechanical rubbing or irradiation with light. The model of this ion generation process is presented and tested using existing experimental data.

Simultaneous Edge‐on to Face‐on Reorientation and 1D Alignment of Small π‐Conjugated Molecules Using Room‐Temperature Mechanical Rubbing

AbstractIn this study, room‐temperature mechanical rubbing is used to control the 3D orientation of small π‐conjugated molecular systems in solution‐processed polycrystalline thin films without using any alignment substrate. High absorption dichroic ratio and significant anisotropy in charge carrier mobilities (up to 130) measured in transistor configuration are obtained in rubbed organic films based on the ambipolar quinoidal quaterthiophene (QQT(CN)4). Moreover, a solvent vapor annealing treatment of the rubbed film is found to improve the optical and charge transport anisotropy due to an increased crystallinity. X‐ray diffraction and atomic force microscopy measurements demonstrate that rubbing does not only lead to an excellent 1D orientation of the QQT(CN)4 molecules over large areas but also modifies the orientation of the crystals, moving molecules from an edge‐on to a face‐on configuration. The reasons why a mechanical alignment technique can be used at room temperature for such a polycrystalline film are rationalized, by the plastic characteristics of the QQT(CN)4 layer and the role of the flexible alkyl side chains in the molecular packing. This nearly complete conversion from edge‐on to face‐on orientation by mechanical treatment in polycrystalline small‐molecule‐based thin films opens perspectives in terms of fundamental research and practical applications in organic optoelectronics.

Improved apple latent spherical virus-induced gene silencing in multiple soybean genotypes through direct inoculation of agro-infiltrated Nicotiana benthamiana extract

BackgroundVirus induced gene silencing (VIGS) is a powerful genomics tool for interrogating the function of plant genes. Unfortunately, VIGS vectors often produce disease symptoms that interfere with the silencing phenotypes of target genes, or are frequently ineffective in certain plant genotypes or tissue types. This is especially true in crop plants like soybean [Glycine max (L.) Merr]. To address these shortcomings, we modified the inoculation procedure of a VIGS vector based on Apple latent spherical virus (ALSV). The efficacy of this new procedure was assessed in 19 soybean genotypes using a soybean Phytoene desaturase (GmPDS1) gene as the VIGS target. Silencing of GmPDS1 was easily scored as photo-bleached leaves and/or stems.ResultsIn this report, the ALSV VIGS vector was modified by mobilizing ALSV cDNAs into a binary vector compatible with Agrobacterium tumefaciens-mediated delivery, so that VIGS-triggering ALSV variants could be propagated in agro-infiltrated Nicotiana benthamiana leaves. Homogenate of these N. benthamiana leaves was then applied directly onto the unifoliate of young soybean seedlings to initiate systemic gene silencing. This rapid inoculation method bypassed the need for a particle bombardment apparatus. Among the 19 soybean genotypes evaluated with this new method, photo-bleaching indicative of GmPDS1 silencing was observed in nine, with two exhibiting photo-bleaching in 100% of the inoculated individuals. ALSV RNA was detected in pods, embryos, stems, leaves, and roots in symptomatic plants of four genotypes.ConclusionsThis modified protocol allowed for inoculation of soybean plants via simple mechanical rubbing with the homogenate of N. benthamiana leaves agro-infiltrated with ALSV VIGS constructs. More importantly, inoculated plants showed no apparent virus disease symptoms which could otherwise interfere with VIGS phenotypes. This streamlined procedure expanded this functional genomics tool to nine soybean genotypes.

Anomalous molecular infiltration in graphene laminates.

Graphene laminated (GL) coatings formed by stacked few layer graphene (FLG) nanocrystals were deposited on low-density polyethylene (PE) films by the mechanical rubbing technique. Molecular transport through the bilayer membrane was studied by the gas phase permeation technique by monitoring the CO2, N2 and 2H2 transport fluxes in transient conditions. The results evidenced that the transport exhibited anomalous character. The experimental data could be reproduced assuming that the penetrant concentration in the GL coating, cint(t), reached a saturation value cs following compressed exponential kinetics cint(t) = cs[1 - e-(λrelt)β]. The relaxation time τrel = 1/λrel showed thermally activated behavior, and its value increased with the kinetic diameter of the penetrant molecules. The critical exponent β = 1.5 ± 0.1 for CO2 and N2 and β = 2.0 ± 0.1 for 2H2 did not change with temperature. Positron annihilation lifetime spectroscopy (PALS) analysis indicated that the average cross-section (hg) of the cavities in the GL coating exhibited comparable size to the kinetic diameter (σk) of the penetrant molecules. The results could be explained by assuming that the molecular infiltration in the GL structure occurred in nano-channels having distributed path lengths where the penetrant transport obeyed a configurational diffusion mechanism.

Assembling of carbon nanotubes film responding to significant reduction wear and friction on steel surface

Friction properties of carbon nanotubes have been widely studied and reported, however, the friction properties of carbon nanotubes related on state of itself. It is showing superlubricity under nanoscale, but indicates high shear adhesion as aligned carbon nanotube film. However, friction properties under high load (which is commonly in industry) of carbon nanotube films are seldom reported. In this paper, carbon nanotube films, via mechanical rubbing method, were obtained and its tribology properties were investigated at high load of 5 to 15 N. Though different couple pairs were employed, the friction coefficients of carbon nanotube films are nearly the same. Compared with bare stainless steel, friction coefficients and wear rates under carbon nanotube films lubrication reduced to, at least, 1/5 and 1/(4.3–14.5), respectively. Friction test as well as structure study were carried out to reveal the mechanism of the significant reduction wear and friction on steel surface. One can conclude that sliding and densifying of carbon nanotubes at sliding interface contribute to the sufficient decrease of friction coefficients and wear rates.

An environmentally friendly method to improve the quality of recycled concrete aggregates

Recycled concrete aggregates (RCAs) have inferior qualities compared with natural aggregates, mainly attributed to the porous nature of the attached cement mortar. To improve the quality of the RCAs, an environmentally friendly and cost-effective method is proposed to treat RCAs in this study. In this method, RCAs are first soaked in acetic acid solution, in which the acetic acid reacts with cement hydration products attached to the surface of the RCAs. This reaction weakens the attached mortar, making it possible to remove it from the RCAs by mechanical rubbing later. The treated RCAs have lower water absorption and less cement mortar attached. Once used as aggregates in new concrete, these RCAs can enhance the compressive strength of the concrete at 28days up to 25%. It is safe and clean to apply this new method since no dangerous chemical is used and no detrimental chemicals are introduced into the treated RCAs. More importantly, zero hazardous waste solution is generated since the waste solution of the treatment can be used to produce high value-added products, permanently store CO2, and regenerate acetic acid. As an example, the waste solution of the treatment was used as admixture for new concrete, which improved the strength of the concrete by 14%.

Rubbing Against Blood Clots Using Helical Robots: Modeling and In Vitro Experimental Validation

The risk of side effects from thrombolytic agents can be minimized by using smaller doses, assisted by mechanical rubbing against blood clots using helical robots. Quantifying this observation, we study the influence of rubbing against clots on their removal rate in vitro. First, we present a hydrodynamic model of the helical robot based on the resistive-force theory to investigate the rubbing behavior of the clots using robot driven by two rotating dipole fields. Second, we experimentally evaluate the influence of the rubbing on the removal rate of the blood clots. Not only do we find that the removal rate of mechanical rubbing (-0.56 ± 0.27 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /min) is approximately three times greater than the dissolution rate of chemical lysis using streptokinase (-0.17 ± 0.032 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /min), but we also show that this removal rate can be controlled via the rubbing speed of the robot.

Large Scale Liquid Crystal Device with Graphene-based Electrodes

AbstractThe new generation Liquid-Crystal Displays (LCDs) will play a key role in modern display industry thus the requirements concerning the response time, power consumption, viewing angles, contrast ratio and easy production stay beyond challenging. In this paper we demonstrate fabrication of large scale liquid crystal device with graphene-based electrodes using a photo-alignment technique. The quality of graphene layer, grown by low pressure CVD method and transferred on the glass substrates was characterized by several techniques: Raman spectroscopy, optical transmittance and electrical measurements. A photo-alignment method instead of commonly used mechanical rubbing technique was used to protect the graphene surface and prevent its partial deattachment from the glass substrates by coating a polyimide layer on the top of graphene. Measured modulation characteristics reveal that the photo-alignment technique possesses great potential for next generation graphene - based LC device fabrication.

Suppressing pretilt angle for enhancing black quality in diagonal viewing angle of homogenously aligned liquid crystal display

ABSTRACTThe diagonal viewing angle light leakage in a black state of in-plane switching (IPS) liquid crystal display (LCD) associated with pretilt angle has been investigated. The mechanical rubbing process with a cloth causes relatively high pretilt angle in the homogenously aligned liquid crystals (LCs) so that the tilted LC director results in increase of a light leakage in a black state at diagonal viewing angles. In this study, we theoretically estimated using classical optic theory how the light leakage in a black state at diagonal viewing angle is associated with the pretilt angle and also proposed an effective method to reduce the pretilt angle from 1.5° to 0° in rubbed IPS LCD by utilising polymer stabilisation. With this approach, we could successfully acquire a better black quality in all viewing angles as compared with normal IPS LCD.

MoS&lt;sub&gt;2&lt;/sub&gt;薄膜摩擦磨损性能及摩擦微观机制研究

MoS2作为一种润滑剂已被广泛应用和研究，但是其在摩擦过程中界面微观结构的变化和摩擦机理相关性很少报道。本文采用机械擦涂方式在不锈钢表面制备了MoS2固体润滑薄膜并考察了与GCr15球、Al2O3球和Si3N4球的摩擦磨损性能。利用场发射扫描电镜(FE-SEM)和拉曼光谱仪(LABRAM HR 800)分别对薄膜结构及其在摩擦过程中结构变化进行表征；利用往复式摩擦磨损试验机(MFT-R4000)、三维表面轮廓仪(MicroXAM-3D)分别研究了薄膜摩擦磨损性能和磨损情况。结果表明：在三种不同对偶条件下所制备的MoS2薄膜均表现出良好的润滑性能，降低接触表面的摩擦系数约80%左右(涂覆前µ~0.5，涂覆后µ~0.1)，同时有效减少不锈钢表面的磨损(5 N时降低18%左右，10 N时降低35%左右)。拉曼光谱证实MoS2薄膜在摩擦力的作用下层状剥离形成磨屑和层间低剪切力是降低摩擦磨损的主要原因。 MoS2 has been widely used and thoroughly studied as a solid lubricant for a long time, but the re-search on relationship of the structure evolution and frictional mechanism are seldomly reported. In this paper, MoS2 solid lubricating films were prepared on the surface of stainless steel by me-chanical rubbing. Then we used GCr15, Al2O3 and Si3N4 ball as couple pairs to investigate the friction and wear properties on a reciprocation tribo-tester (FMT-R4000), the loads for tests were 5 N and 10 N. Field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy revealed the structure evolution of MoS2 during the course of friction. Three-dimensional surface profiler (MicroXAM-3D) was used to characterize the surface topography of wear tracks. The results indi-cated that the friction coefficient of stainless steel was reduced by 80% (before coating ~0.5 and af-ter coating ~0.1), and the wear volume was reduced by 18%, 35% when the load was 5 N and 10 N, respectively. These excellent properties suggest that mechanical rubbing is an effective method for solid lubricating film preparation. In addition, Raman spectroscopy also confirmed that the layered peeling and interlayer low shear is the main reason to reduce friction and wear.

Polarized Emission from Conjugated Polymer Chains Aligned by Epitaxial Growth during Off-Center Spin-Coating

Due to their macromolecular nature, conjugated polymers can be relatively easily aligned by applying a variety of processes resulting in either elongation or ordering of their conjugated backbones. Processes that induce chain alignment include electrospinning, mechanical rubbing, epitaxial growth, and nanoconfinement and unidirectional deposition techniques such as off-center spin-coating. In this study, we compare these deposition techniques by applying them to a green-emitting conjugated polymer material that exhibits liquid crystalline phase behavior. Our study reveals that while methods such as electrospinning and mechanical rubbing can be useful to locally generate polymer chain alignment, the combination of epitaxial growth using 1,3,5-trichlorobenzene as crystallizing agent with off-center spin-coating results in the formation of anisotropic nanofiber-like structures with enhanced crystallinity degree and polarized light-emission properties. The unidirectional epitaxial growth was also applied to a red-emitting polymer that exhibits polarization ratios up to 4.1. Our results emphasize that this simple solution formulation and process can be used for the fabrication of polarized thin films of a variety of conjugated polymers with potential applications in the advanced display technologies or analytical equipment fields.

Release of Moxifloxacin from Contact Lenses Using an In Vitro Eye Model: Impact of Artificial Tear Fluid Composition and Mechanical Rubbing.

PurposeThe aim of this study was to evaluate and compare the release of moxifloxacin from a variety of daily disposable (DD) contact lenses (CLs) under various conditions using a novel in vitro eye model.MethodsFour commercially available DD conventional hydrogel (CH) CLs (nelfilcon A, omafilcon A, etafilcon A, and ocufilcon B) and three silicone hydrogel (SH) CLs (somofilcon A, narafilcon A, and delefilcon A) were evaluated. These lenses were incubated in moxifloxacin for 24 hours. The release of the drug was measured using a novel in vitro model in three experimental conditions: (1) phosphate buffered saline (PBS); (2) artificial tear solution (ATS) containing a variety of proteins and lipids; and (3) ATS with mechanical rubbing produced by the device.ResultsOverall, CH CLs had a higher drug release than SH CLs (P < 0.05) under all conditions. Typically, a higher drug release was observed in PBS than ATS (P < 0.05). For CH, drug release was found to be higher in ATS with rubbing than PBS or ATS (P < 0.05). For most lens types, ATS with rubbing produced higher drug release than ATS alone (P < 0.05). Generally, the release kinetics for all conditions were sustained over the 24-hour testing period, and no burst release was observed (P < 0.05).ConclusionsMoxifloxacin release from a CL into ATS is lower when compared to release into PBS. When mechanical rubbing is introduced, the amount of drugs released is increased.Translational RelevanceResults suggest that sophisticated in vitro models are necessary to adequately model on-eye drug release from CL materials.

Optimisation of alignment materials for minimising residual retardation in in-plane switching liquid crystal display

ABSTRACTThe light leakage in a black state of in-plane switching (IPS) liquid crystal display (LCD) associated with rubbing process has been investigated. The mechanical rubbing process with a cloth caused orientation disorders in the liquid crystal directors and these partial orientation disorders result in residual retardations of the IPS LCD, causing the light leakages at the black state. In this study, we theoretically estimated how the light leakage is associated with the rubbing uniformity using 2 × 2 Jones matrix equation and also experimentally confirmed how it is associated with structural properties of the alignment layer. The light leakage was clearly reduced in the alignment layer with reduced crystallinity and flexibility.

Ferroelectric BaTiO3 and LiNbO3 nanoparticles dispersed in ferroelectric liquid crystal mixtures: Electrooptic and dielectric parameters influenced by properties of the host, the dopant and the measuring cell

ABSTRACTHarvested ferroelectric nanoparticles of BaTiO3 and LiNbO3 were dispersed in Ferroelectric Liquid Crystals (FLCs) with very high spontaneous polarization (Ps). The electrooptic and dielectric parameters were documented. The dipoles of ferroelectric nanoparticles and those of FLCs are partially cancelled in an antiparallel manner. The role of cell parameters like thickness of the Nylon 6 polymer layer and the change in preparation of the polymer layer due to different mechanical rubbing cycles has been described for one high-Ps FLC and for high-Ps FLC/BaTiO3 nanocolloids. Cell properties depend strongly on anchoring forces which might interact with dipoles both from ferroelectric nanoparticles and high-Ps FLCs.

Rationally Designed Dynamic Superstructures Enabled by Photoaligning Cholesteric Liquid Crystals

a proper electric fi eld, simple grating with parallel stripes are produced in uniformly aligned cells. [ 14 ] Unfortunately, the defects induced by conventional mechanical rubbing technique signifi cantly interrupt the continuity of helical axis, thus it is diffi cult to get orderly arranged stripes with a uniform periodicity (Figure S1, Supporting Information). That is why the so-called “fi ngerprint” nonuniform textures are usually reported. [ 15 ] Moreover, the capability to manipulate the in-plane helical axes to realize more complex stripe pattern remains highly restricted. Based on the CLC in-plane aligned helical axis structure, diffraction gratings [ 16 ] and lithography mask [ 17 ] have been demonstrated. Moreover, the variation of the period of CLC grating [ 14,18 ] and its rotation [ 19 ] make it an excellent candidate for nonmechanical beam steering devices. Thus, the capability of generating high-quality CLC superstructures with ordered orientation and reliable periodicity is crucial for above applications. However, as mentioned above, the low quality and poor controllability of the self-assembled CLCs make the task very formidable. Furthermore, the present mechanical aligning technique is only suitable to produce 1D [ 14,20 ] or 2D gratings. [ 21 ]

Nanotube-based source of charges for experiments with solid helium at low temperatures

Methods of preparation of the field-emission sources of charges from carbon nanotubes suitable for study of injected charges in solid helium at low temperatures T < 1 K are presented. The sources have been prepared by arc discharge deposition of nanotubes onto a flat copper substrate or by mechanical rubbing of nanotubes into porous metal surface. The test study of the voltage-current characteristics of a diode cell with the nanotube source in superfluid He II have shown that at voltages above 120 V one can observe a relatively large current I ≥ 10–13 A of negative charges in liquid helium. The field and temperature dependences of positive and negative currents in solid 4He were studied in samples grown by the blocked capillary technique. Usage of the nanotube based source of injected charges had permitted us for the first time to observe motion of the positive charges in solid helium at temperatures below 0.1 K. The current-voltage dependence could be described by a power law I∼Uα, with the value of the ...