Soft contact lenses are medical devices made from aqueous polymeric gels that are worn on the eye to correct refractive errors. These devices interrupt the natural contact pairing between the cornea and the eyelid and create two interfaces comprised of a synthetic material and the epithelia—contact lens surfaces versus (1) the cornea and (2) the eyelid conjunctiva. The cellular responses to friction

MoS2:glycol hybrid nanoparticles were synthetized through a polyol route. Their tribological properties when used as lubricant additives in a PAO 6 base oil were investigated using a pin-on-disk tribometer. An important friction reduction and good anti-wear performances were observed compared to the base oil and to the no modified particles. The MoS2:glycol nanoparticles were characterized by thermogravimetric

Oleylamine (hereinafter referred to as OM)-modified CeO2 nanoparticles were synthesized by a one-pot pyrolysis method. The tribological properties of the as-prepared CeO2 nanoparticles as the lubricant additive in poly-alpha olefin (PAO) were investigated with a four-ball machine, and their lubricating mechanism was discussed in relation to worn surface analyses by SEM, EDS, and XPS. Findings indicate

Friction of textiles on the human forearm is an important factor in comfort sensations of garments. We built an experiment to measure friction for textiles sliding on the forearm under loading conditions which are characteristic for wearing shirts or jackets. The hair coverage of the participants’ forearm was quantified by image analysis of photographs of the arm in the region of contact. Friction

This work investigates in situ friction-generated copper nanoparticles at the sliding in the precursor solution of copper formate tetrahydrate and octylamine, which induced by frictional heat, it can effectively mitigate wear while slightly reducing friction coefficient. The frictional heat between tribo-pairs accelerated the decomposition of the precursor into in situ generated copper nanoparticles

The original publication contained an incorrect mention of the time duration for Fig. 12 in Appendix. The expanded friction curve is for the initial 30 s of sliding.

Titanium alloys are used for their good mechanical and corrosion properties, but generally experience poor wear behavior. This can effectively be counteracted by a thermal oxidation treatment, reducing wear significantly. Employing a special sample preparation, we study the transition of tribological properties between thermally oxidized and bulk Ti6Al4V on a single sample. While oxygen signal intensity

Water-based cutting fluid (WCF) is more and more widely used in metal processing to meet the requirements for advanced manufacturing nowadays. However, the utilization of WCF is disputed for low wettability, which causes unstable lubrication. A new type of graphene oxide (GO)-based Pickering emulsion was developed as WCF due to the superior performance of GO in lubrication. Functionalized GOs (fGOs)

In the present study, nanoscale friction and wear behavior of the AZ91 alloy with respect to crystallographic orientations (basal, pyramidal and prismatic) were examined. The hardness of different crystallographic orientation was measured using nanoindentation. Load-dependent friction and wear behavior was investigated using atomic force microscopy (AFM). Electron back scattered diffraction (EBSD)

From the industrial view point, an automated classification system of worn surfaces is highly desirable for the monitoring and prediction of the operational health status of machines and their components. Optical microscopy images of abrasive and adhesive wear surfaces were obtained and analyzed using recently developed directional blanket covering (DBC) and DBC curvature (DBCC) methods. As these methods

We recently reported the use of cyclopropanecarboxylic acid (CPCa) as a model additive that can readily react under the combined effect of flash heating and stress in steel tribocontacts to form tribopolymers, along with marked improvement in tribological performance. In this paper, we present results of how chemical structural modification of CPCa may impact on the formation of tribopolymers and hence

Human beings use certain styles when perceiving physical characteristics of objects with fingers. Sliding direction of finger contact is among the aforementioned styles. Thus, understanding the effect of sliding direction on tactile perception is essential. This study investigated the perception and identification of the roughness of sandpapers in two different sliding directions: proximal and distal

Taking 1,4-naphthalene dicarboxylic acid (1,4-ND), 2,3-naphthalene dicarboxylic acid (2,3-ND) and tetrabutyl ammonium hydroxide (N4444OH), tetrabutyl phosphonium hydroxide (P4444OH) as raw materials, water-based lubricant additives tetrabutyl ammonium 1,4-naphthalene dicarboxylate (1,4-NDN4444), tetrabutyl phosphonium 1,4-naphthalene dicarboxylate (1,4-NDP4444), tetrabutyl ammonium 2,3-naphthalene

A novel molecular model of vulcanized styrene-butadiene rubber (SBR) was developed and experimentally verified to elucidate the enhanced tribological performance of vulcanized SBR over raw SBR. Vulcanization was modeled by cross- or self-linkages of sulfur (S) atoms with carbon (C) atoms in molecular chains. Frictional models were developed for vulcanized and raw styrene-butadiene rubber-ferrum (SBR-Fe)

The mucous layer on the surface of human digestive tract is a dynamically balanced protective system, mainly containing mucin, enzymes, bicarbonate, epidermal growth factor and other protective factors. It has been found that mucins can protect epithelial cells from infection, dehydration, and physical, mechanical or chemical damage. There are a variety of disturbances that affect or destroy the function

A number of authors have experimentally assessed the influence of friction on adhesive contacts, and generally the contact area has been found to decrease due to tangential shear stresses at the interface. The decrease is however generally much smaller than that predicted already by the Savkoor and Briggs 1977 classical theory using “brittle” fracture mechanics mixed mode model extending the JKR (Griffith

We conducted atomic force microscopy (AFM) experiments by sliding hard tetrahedral amorphous carbon (ta-C)-coated and diamond AFM probes against silicon oxide-doped hydrogenated amorphous carbon (a-C:H:Si:O) films. We reproducibly observe a substantial reduction in friction with repeated sliding. This behavior qualitatively resembles the run-in effects generally seen in macroscale frictional sliding

The MoS2 quantum dots less than 10 nm were in situ prepared in green ILs for the first time. The MoS2 quantum dots can be easily obtained by simple one-step synthesis within the preparation of ILs themselves. The physico-chemical and tribological properties of the acquired the MoS2 QDs in ILs were systematically studied. Compared with pure ILs, the MoS2 QDs in ILs exhibiting long-term dispersion stabilities

Squeeze film force exists but is undesirable in some engineering applications such as immersion lithography and micro-electro mechanical systems. The dynamic characteristics of such systems can be improved by adopting hydrophobic surfaces. In addition to squeeze film damping effects, slip effects are prominent and the inertial effects can be neglected with small film thickness, while inertial effects

The detailed deformation mechanism and its microstructural modifications of white cast iron grinding balls used in comminution have been investigated using transmission electron microscopy (TEM) and XRD. De-shaping is the primary mode of ball consumption, and fracture of balls is a relatively uncommon failure mode. Deshaping is the manifestation of abrasive wear caused during the operation, and abrasive

This study aims at exploring the wear performance of AISI 316L stainless steel fabricated via selective laser melting along different directions with respect to the building direction and via post annealing. Here, the wear resistance of the material was investigated via ball-on-disk tribology tests under a quasi-stationary condition, i.e., with linear sliding speeds in the range of 25–100 mm/s. The

The film-forming, friction and wear properties of a range of model and commercial ashless P and P/S antiwear additives have been studied. A method has been developed for removing the tribofilms formed by such additives in order to effectively quantify mild wear. In general the P/S additives studied formed thinner tribofilms but gave lower wear than the S-free P ones. In extended wear tests, three P/S

In an elastohydrodynamic lubricated (EHL) contact under Zero Entrainment Velocity (ZEV) condition, surfaces cannot be separated by hydrodynamic lift. In this work, two other phenomena responsible for a film thickness build-up in ZEV contacts are studied using a numerical model. First, the thermal effect called “viscosity wedge” is investigated in steady-state conditions. Second, the “squeeze” effect

We present a new technique designed for in situ measurement of pressure and temperature in lubricating films. An innovative methodology has been developed, based on the photoluminescence properties of non-intrusive CdSe-based nanosize sensors (quantum dots). The sensitivity to pressure and temperature of these sensors dispersed in a carrier fluid was established through calibrations performed in diamond

AbstractThe active control of friction in oil-based lubricants was realized in the present study with the use of MoS2 particle additives and the application of an electric field. By modifying the surface charging state of the MoS2 particles, the dependence of potential-controlled boundary lubrication behavior on the electrical properties of the particles was demonstrated. For a diethyl succinate lubricant

The application of polymers in power-transmitting machine elements, e.g., gears, is limited by moderate thermo-mechanical properties and the detrimental accumulation of contact heat, even with external lubrication. Hence, polymer rolling–sliding elements are often prone to thermo-mechanical overload or abrasive wear. Diamond-like carbon (DLC) coatings are well known from steel applications for enhancing

The performance of micro/nanoelectromechanical systems (MEMS/NEMS) relies on efficient lubrication. In the present work, new sulfur-based organic salts were tested as additives in a polyethylene glycol to lubricate silicon surfaces used in the manufacture of MEMS/NEMS. Seven salts were tested: 1-butylsulfonic-3-methylimidazolium triflate [(C4SO3H)MIM][TfO], thiamine triflate [Thiamine][TfO]2, 1-et

Although the efficiency of a gear pair is currently high, a better understanding of surface/lubricant contribution on efficiency is critical. Electrified drivelines will, for example, impose higher speed and alternate loading, and it is expected that these new conditions will, to a greater extent, rely on the surface/lubricant characteristics. Phenomena taking place in the gear contact is often measured

The original version of this article unfortunately contained a mistake. The affiliation information was incorrect for the co-authors Shigeru Tazawa, Tsuyoshi Urano, Shinji Kobayashi.

AbstractPTFE composite wear rates are known to vary by 1000 × depending on the size and strength of their nanofiller aggregates. While these effects have been attributed to variations in subsurface reinforcement, debris regulation, transfer films, and filler abrasivity, the chain of causation has proven difficult to test. This study aimed to clarify these causal relationships by eliminating confounding

The solid particle erosion of polymers occurs in a wide variety of industries and has been extensively studied experimentally. However, numerical models capable of accurately simulating the associated material removal mechanisms and predicting erosion rate do not yet exist. In this paper, a coupled smoothed particle hydrodynamics (SPH)/finite element (FE) model was developed to simulate the erosion

Mechanical seal is installed in EVAHEART®, one of left ventricular assist device, which supports the role of original human heart. Low friction and low leakage are both required for mechanical seal for ventricular assist device to realize longer battery lifetime and less maintenance. In this study, several types of surface texture by combination of laser-induced periodic surface structure (LIPSS) and

To understand the dissipative mechanisms in soft hydrogel lubrication, polyacrylamide (PAAm) hydrogels with two distinct surface structures were examined under various contact conditions. The characteristic speed-dependent friction of the self-mated, crosslinked hydrogel surfaces could be explained by hydrodynamic shearing of a thin water layer between two rather impermeable bodies. On the other hand

Self-assembled monolayers (SAMs) can reduce friction in boundary lubricated contacts by providing a low shear strength interface for sliding. However, the nanoscale mechanisms underlying low friction on SAMs are still not fully understood, especially in liquid environments in which hydrophobility or hydrophilicity affects friction. To understand this effect, friction of SAMs in water was measured using

Soy-based fatty acid methyl ester disulfide (FAME-S2) was synthesized in good yield by oxidation of polymercaptanized soybean oil fatty acid methyl ester (PM-FAME). The chemical structure of FAME-S2 is of interest because of its potential as a biobased multi-functional additive in lubricant formulations. Neat FAME-S2 and their blends (1–10% w/w) in polyalphaolefin (PAO-6) and high oleic sunflower oil

There are a number of widely used machine components, such as rolling element bearings, gears and cams, which operate in the lubrication regime known as Elastohydrodynamics (EHD), where lubricant film thickness is governed by hydrodynamic action of convergent geometry, elastic deformation between non-conformal contacting surfaces, and the increase of lubricant viscosity with pressure. Variable loading

To investigate dry wear behavior in an aluminum-based automotive alloy, transient horizontal solidification experiments using a water-cooled directional solidification device have been performed with the Al7Si0.3Mg alloy (wt%). Samples of the as-cast ingot at positions (P) 2, 4, 6, 40, and 80 mm from the cooled interface were subjected to precipitation hardening heat treatment (T6-type). The heat treatment

AbstractThermocapillary migration describes an interfacial phenomenon that liquids can spontaneously move from the warm to the cold regions on nonuniformly heated solids. However, it is unknown how liquids react at various interfaces subjected to a thermal gradient. In this study, migration of liquid lubricants at the free surface, the plate/plate interface, and the sphere/plate interface is investigated

The aim of this study was to evaluate the effect of dissolution of the small carbides residual from annealing and earlier processing, on the mechanical and wear properties of hot-work tool steel. Recommended as well as extreme austenitization temperatures (950 °C, 1030 °C and 1150 °C) with subsequent tempering were used aiming at same hardness level of specimens of same material. This allows correlation

Several two-dimensional (2D) materials such as graphene, molybdenum disulfide, or boron nitride are emerging as alternatives for lubrication additives to control friction and wear at the interface. On the other hand, the initiative to accelerate materials discovery through data-driven computational methods has identified numerous novel topologies and families of 2D materials that can potentially be

Indentation tips are never atomically sharp, but rounded at their end. We use atomistic simulation to study the effect of tip roundness for the particular case of a cube-corner pyramidal indenter by comparing the results of a spherical, a sharp cube-corner, and a rounded cube-corner tip during indention into bcc Fe. We find that as soon as the tip has indented so deeply that the spherical geometry

Friction is an important limitation of energy efficiency performances of MEMS/NEMS but is, in the same time, a great opportunity for harvesting energy by designing optimized tribo-electric nano-Generators (TENG). Thus, frictional behaviour can be accurately controlled in real time by using thermally sensitive periodic patterned self-assembled monolayers of n-octadecyltrichlorosilane (OTS) grafted on

Highly loaded lubricated contacts may present a friction plateau on which the friction force becomes independent from the sliding velocity. Although this phenomenon has been known for a long time, its physical origin remains poorly known. The present paper aims at giving further insight on the physical mechanisms triggering the friction plateau. The study specifically focuses on the influence of pressure

This paper investigates the tribological and related properties of naturally modified beech wood (Fagus sylvatica). The modifications were performed on steamed beech wood using a variety of treatments consisting of drying, heating in an aqueous solution, impregnation with liquefied animal glue as well as beeswax followed by compression and various combinations thereof. Results indicate that an impregnation

Oleamide and Synovene lubricant additives when mixed together show a clear co-operative effect leading to friction and wear reduction. Sum Frequency Generation vibrational spectroscopy has been used to record in situ spectra of these additives with the aim of understanding the behaviour of these molecules when adsorbed on steel immersed in a model base oil at pre-selected temperatures. The spectra

Materials providing high resistance to wear and macro-deformations or impacts are needed for many applications (material handling hoses or flexible ducting systems, snow plow cutting edges, human joint prostheses, Mars rover wheels, etc.). Production of wear-resistant materials using the promising approach of additive manufacturing (AM) is currently of great interest. Specific nature-inspired or -mimicking