Rough Glass Surfaces Research Articles

Vesicle formation of single-tailed amphiphilic alkyltrimethylammonium bromides in water induced by dehydration-rehydration.

We recently found that rough glass surfaces (RGSs) can in situ mediate the micelle-to-vesicle transition in single-component solutions of simple single-tailed amphiphiles (STAs), but only result in a relatively small number of vesicles coexisting with a large number of micelles. In the current work, a dehydration-rehydration (DHRH) method was used to induce the formation of vesicles in the single-component aqueous solutions of alkyltrimethylammonium bromides (CnTABs, n = 12, 14, and 16), a kind of typical cationic STAs. That is, a CnTAB micelle solution dropped on smooth glass surfaces (SGSs) was first dried, and the dried CnTAB aggregates were then rehydrated in a monomer solution of CnTAB. A large population of vesicles and even pure vesicle (or vesicle-dominated) systems were obtained, indicating that the DHRH process could more effectively induce the formation of STA vesicles than RGS in situ mediation. The so-obtained vesicles were characterized using DLS, FF-/cryo-TEM, AFM, SAXS, and fluorescence techniques, and their stability was determined. In addition, the effects of the conditions of DHRH and the chain length of CnTABs on the vesicle formation were examined. It was demonstrated that the vesicles can be formed as long as the concentrations of CnTABs in the rehydrated systems are higher than their critical micelle concentrations. The size and wall thickness of vesicles increase with an increase in chain length. A possible mechanism for the DHRH-induced vesicle formation is proposed: bilayer sheets are formed on SGSs during dehydration, and then detached from the SGSs to form vesicles during rehydration. A highly interdigitated structure of alkyl chains between two leaflets was identified in the bilayers, which probably is the origin of the formation and stability of STA vesicles.

The Direct Cause of Amplified Wettability: Roughness or Surface Chemistry?

Higher contact angles or amplified wettability observed on surfaces of rough solid materials are typically expressed as a function of a physical dimension (roughness factor). Herein, we present a simple experimental approach that demonstrates that roughness may only magnify the inherent surface chemistry that seems to have direct influence on surface wettability. We investigate gradual change in surface chemistry (hydrophobisation) of rough and smooth glass surfaces, from a very low concentration (10−7 M) of dichlorodimethylsilane, DCDMS through various intermediate hydrophilic/hydrophobic states to when the surfaces are maximally hydrophobised with DCDMS at 0.1 M. The wettability of the modified glasses was studied by water contact angle measurements using drop shape analysis system (DSA). The data obtained indicate a deviation from Wenzel model, with the functionalized rough glass surfaces showing higher reactivity towards DCDMS when compared to the smooth glass surfaces, indicating that the two surfaces are not chemically identical. Our study reveals that just like transforming a solid material to powder, a well-divided glass (rough) surface may not only exhibit a greater surface area than the smooth counterpart as rightly predicted by the Wenzel model, but seems to be bloated with functional groups (–OH or –CH3) that can amplify surface interaction when such functional species dominate the solid surface.

The Effect of Roughness on the Wet Skid Resistance of Tire Tread Compounds

The wet skid resistance is the main performance of automobile tires, and the excellent wet skid resistance can ensure the safety of the car. In this paper, 60 mesh sandpaper, 400 mesh sandpaper, 1000 mesh sandpaper and 2000 mesh sandpaper were used to pre-grind the sample, which changed the surface roughness of the sample; measured the dry and wet friction coefficient of the sample, and the measured friction pair was smooth Glass surface, rough glass surface and 180 grit sandpaper surface. The experimental results show that the rougher the surface of the sample and the surface of the friction pair, the greater the wet friction coefficient and the better the wet skid resistance.

Large-aperture ground glass surface profile measurement using coherence scanning interferometry.

We present a coherence scanning interferometer configured to deal with rough glass surfaces exhibiting very low reflectance due to severe sub-surface light scattering. A compound light source is prepared by combining a superluminescent light-emitting diode with an ytterbium-doped fiber amplifier. The light source is attuned to offer a short temporal coherence length of 15 μm but with high spatial coherence to secure an adequate correlogram contrast by delivering strongly unbalanced optical power to the low reflectance target. In addition, the infrared spectral range of the light source is shifted close to the visible side at a 1,038 nm center wavelength, so a digital camera of multi-mega pixels available for industrial machine vision can be used to improve the correlogram contrast further with better lateral image resolutions. Experimental results obtained from a ground Zerodur mirror of 200 mm aperture size and 0.9 μm rms roughness are discussed to validate the proposed interferometer system.

Pore-scale study of thermal fields during evaporation from drying porous surfaces

The drying of a porous surface and subsequent pore emptying resemble a sequence of drainage whereby pores are invaded according to their respective capillary size (large pores are invaded first). The emptying of pores modifies both the local evaporative fluxes and surface thermal fields adjacent to invaded pores. These local adjustments could result in a gradual decrease in evaporation rate and a potential increase in surface temperature thereby altering energy partitioning over the drying surface as described by the Pore-scale Coupled Energy Balance (PCEB) model of Aminzadeh and Or (2014). This study aims to observe and quantify these dynamic pore-scale mass and energy interactions to test key assumptions in the basis of the PCEB model and gain new insights into these important processes. We used a novel experimental system consisting of individual and clustered evaporating pores drilled into rough glass surfaces. Thermal fields around individual evaporating pores and their interactions were observed using highly resolved infrared imager under different radiative fluxes. Thermal observations and direct measurements of evaporative fluxes were in good agreement with predictions by the PCEB model. Drying of a glass beads surface was captured by optical and thermal imaging to provide links between pore emptying sequence and surface thermal adjustments. The results highlight the upscalability of pore-based representation of surface drying and the predictability of energy partitioning over drying porous surfaces.

The formation and stability of sodium dodecylsulfate vesicles mediated by rough glass surface

Under the mediation of a rough glass surface (RGS), formation of vesicles was realized from a micellar solution of only a simple anionic single-tailed surfactant (STS), sodium dodecylsulfate (SDS), to form a mixed solution of micelles and vesicles. Interestingly, the SDS vesicles formed in the solution displayed good stability upon long-term storage, exposure to high temperature, freeze–thawing, and high salinity after the RGS removal. Adsorption and water contact angle measurements demonstrated that SDS could adsorb on the RGS to form bilayers in which the molecular packing parameter of SDS was in the range of 1/2–1. The bilayer adsorption and the roughness of the solid surface played an important role in vesicle formation. AFM observations suggested that the alkyl tails of SDS in the vesicular bilayer membranes were partially interdigitated, and molecular dynamics simulations revealed that the partially interdigitated bilayer structure is crucial for the formation and stability of the SDS vesicles. This work contributes to the understanding of the nature of vesicle systems.

Viscous surface flow induced on Ti-based bulk metallic glass by heavy ion irradiation

Ti-based bulk metallic glass was irradiated by a 20MeV Cl4+ ion beam under liquid-nitrogen cooling, which produced remarkable surface smoothing and roughening that respectively correspond to normal and off-normal incidence angles of irradiation. Atomic force microscopy confirms two types of periodic ripples distributed evenly over the rough glass surface. In terms of mechanism, irradiation-induced viscosity agrees with the theoretical prediction for metallic glasses near glass transition temperature. Here, a model is introduced, based on relaxation of confined viscous flow with a thin liquid-like layer, that explains both surface smoothing and ripple formation. This study demonstrates that bulk metallic glass has high morphological instability and low viscosity under ion irradiation, which assets can pave new paths for metallic glass applications.

Stick-slip friction of gecko-mimetic flaps on smooth and rough surfaces.

The discovery and understanding of gecko 'frictional-adhesion' adhering and climbing mechanism has allowed researchers to mimic and create gecko-inspired adhesives. A few experimental and theoretical approaches have been taken to understand the effect of surface roughness on synthetic adhesive performance, and the implications of stick-slip friction during shearing. This work extends previous studies by using a modified surface forces apparatus to quantitatively measure and model frictional forces between arrays of polydimethylsiloxane gecko footpad-mimetic tilted microflaps against smooth and rough glass surfaces. Constant attachments and detachments occur between the surfaces during shearing, as described by an avalanche model. These detachments ultimately result in failure of the adhesion interface and have been characterized in this study. Stick-slip friction disappears with increasing velocity when the flaps are sheared against a smooth silica surface; however, stick-slip was always present at all velocities and loads tested when shearing the flaps against rough glass surfaces. These results demonstrate the significance of pre-load, shearing velocity, shearing distances, commensurability and shearing direction of gecko-mimetic adhesives and provide us a simple model for analysing and/or designing such systems.

Rough glass surface-mediated transition of micelle-to-vesicle in sodium dodecylbenzenesulfonate solutions.

In this paper, we report a micelle-to-vesicle transition in aqueous solution of the anionic single-tailed surfactant (STS) sodium dodecylbenzenesulfonate (SDBS), with the mediation of a rough glass surface (RGS) in the absence of cosurfactants or additives. This transition produced a mixed solution of vesicles and micelles. Interestingly, the obtained SDBS vesicles in the solution displayed good stability during a long-term storage (at least 6 months at room temperature), exposure to high temperature (80 °C for 2 h), and freeze-thawing (-20 or -196 °C for 2 h to approximately 25 °C) after the RGS was removed. Our results confirmed that SDBS could adsorb on the RGS to form bilayers, in which the molecular packing parameter of SDBS was in the range of 1/2-1. The bilayer adsorption and the roughness of the solid surface played an important role in the vesicle formation. In addition, we propose a possible mechanism for the RGS-mediated transition of micelle-to-vesicle in SDBS solutions: SDBS micelles and molecules adsorb on the RGS to form curved bilayers; the curved bilayers detach from the RGS, and then close to form vesicles.

Rough glass surface-mediated formation of vesicles from lauryl sulfobetaine micellar solutions.

We report novel vesicles composed of the zwitterionic surfactant lauryl sulfobetaine (LSB), which is a simple single-tailed surfactant (STS). The novel vesicles spontaneously formed from LSB micellar solutions with the mediation of a rough glass surface (RGS) in the absence of any cosurfactants or additives. Importantly, the obtained STS vesicles displayed good stability upon long-term storage, exposure to high temperature, and freeze-thawing after the RGS was removed. The pH of the LSB solution (4.0-9.0) and the presence of NaCl (1.0 × 10(-5) and 1.0 × 10(-4) mol/L) in the LSB solution had no obvious influence on the formation and stability of the vesicles. The adsorption configuration of LSB on the RGS was investigated via water contact angle measurements and atomic force microscope observations. The results showed that LSB adsorption bilayers could form on the RGS, and the bilayer adsorption of LSB on the RGS and the roughness of the solid surface played a key role in the vesicle formation. A possible mechanism for the RGS-mediated formation of LSB vesicles is proposed: LSB micelles and molecules adsorb on the RGS to form curved bilayers, and the curved bilayers are then detached from the RGS and close to form vesicles. To the best of our knowledge, this is the first report of LSB alone forming vesicles. This finding extends our understanding of the nature of vesicle systems.

Shaping the scattering pattern by means of asperities at a glass boundary

This paper presents a study and comparison of the optical properties of rough glass surfaces obtained by various methods. It is shown that, when a rough surface is created by means of grinding powders with a grain size of from 10 to 40 μm, the width of the scattering pattern increases to 35°, but the amount of transmitted radiation is reduced in this case because of internal reflections. It is pointed out that the creation of a rough surface by means of etching provides a narrower scattering pattern but reduces the losses of transmitted radiation.

Fabrication of nano-structures on glass substrate by modified nano-imprint patterning with a plasma-induced surface-oxidized Cr mask

In this study, we introduce a process for fabrication of nano-sized structural arrays on glass using modified nano-imprint patterning. A PVC (polyvinyl chloride) stamp was prepared by hot embossing, and a Cr-oxide-pattern etch-mask was used. The etch-mask was formed by oxidizing the surface of exposed Cr region by oxygen plasma treatment at room temperature. The fabrication of the etch-mask was conducted by immersing the locally oxidized Cr pattern in resin remover and Cr-etchant. The residual UV resin and un-oxidized Cr pattern were selectively removed, resulting in the obvious array of Cr-oxide etch-mask-pattern. The array of glass nano-structures was formed by reactive ion etching (RIE) using CF4 and Ar gas discharge. After removing the Cr-oxide mask, the final nano-structure had a height of 40 nm and a diameter of 170 nm, which was slightly less than the diameter of the original master-mold. The plasma treatment gave rise to a rough glass surface with root-mean-square (RMS) roughness of 29.25 nm, while that of bare glass was 0.66 nm. A high optical transmittance due to reduction in reflectance was observed at the plasma-treated rough surface, as well as for the array of nano-structures. The highest measured optical transmittance was 97.2% at a wavelength of 550 nm; an increase of about 7.2% compared to bare glass.

Vesicles composed of one simple single-tailed surfactant.

Novel vesicles formed spontaneously from the micelle solution of DTAB, a single-tailed surfactant (STS), mediated by a rough glass surface (RGS) without any additives. The obtained STS vesicles displayed good stability upon long-term storage, exposure to high temperatures, and freeze-thawing after the removal of RGS.

Flat Dry Elastomer Adhesives as Attachment Materials for Climbing Robots

In this paper, flat elastomers are proposed as an attachment material for climbing robots on less than a few micrometer-scale rough surfaces due to their energy-efficient, quiet, and residue-free characteristics. The proper elastomer is chosen by the use of the current adhesion, friction, and peeling elastomer-contact-mechanics models. Then, adhesion and friction properties of the chosen dry flat-elastomer thick films (Vytaflex-10) are characterized on acrylic and smooth and rough glass surfaces for variations in preloads, speeds, contact times, and elastomer thicknesses. A climbing robot with four-bar-based legged-body kinematics is designed and fabricated as simple and lightweight as possible to demonstrate the feasibility of the elastomers as attachment materials on relatively smooth surfaces. The robot utilizes a passive alignment system to make the footpads parallel to the surface on light contact, a peeling mechanism to minimize the detachment vibration, and a passive tail to minimize the pitch-back moment. Experimental results showed that the robot can climb stably on vertical, smooth surfaces in any direction and can walk inverted for a limited amount of time.

Friction of human skin against smooth and rough glass as a function of the contact pressure

The friction behaviour of human skin was studied by combining friction measurements using a tri-axial force plate with skin contact area measurements using a pressure sensitive film. Four subjects carried out friction measurement series, in which they rubbed the index finger pad and the edge of the hand against a smooth and a rough glass surface under dry and wet conditions. The normal loads were varied up to values of 50 N, leading to skin contact pressures of up to 120 kPa. The analysis of the pressure dependence of friction coefficients of skin for contrasting sliding conditions allowed to determine the involved friction mechanisms on the basis of theoretical concepts for the friction of elastomers. Adhesion was found to be involved in all investigated cases of friction between skin and glass. If adhesion mechanisms predominated (skin against smooth glass in the dry condition and skin against rough glass in the wet condition), the friction coefficients were generally high (typically >1) and decreased with increasing contact pressure according to power laws with typical exponents between −0.5 and −0.2. Contributions to the friction coefficient due to viscoelastic skin deformations were estimated to be relatively small (<0.2). In those cases where the deformation component of friction played an important role in connection with adhesion (skin against rough glass in the dry condition), the friction coefficients of skin were typically around 0.5 and their pressure dependence showed weak trends characterised by exponents ranging from −0.1 to +0.2. If hydrodynamic lubrication came into play (skin sliding on smooth glass in the wet condition), the friction coefficients were strongly reduced compared to dry friction (<1), and their decrease with increasing contact pressures was characterised by exponents of <−0.7.

Product decomposition of measured Mueller matrices from the FLC based NIR Mueller Matrix Ellipsometer

AbstractThis paper reports on the application of the first near‐infrared spectroscopic Mueller Matrix Ellipsometer (MME) based on Ferro‐electric Liquid Crystal retarders (FLC) and fixed waveplates. Operation of the instrument is demonstrated by transmission Mueller matrix measurements, and product decomposition of an imperfect dichroic polarizer and a depolarizing rough glass surface. The decomposition of the measured matrices is qualtitatively discussed in terms of retardance, diattenuation, depolarization, and azimuthal orientation. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Observation of light transmission through randomly rough glass surfaces beyond the critical angle

In this series of experiments we study the transmission of laser light through a randomly rough interface between air and ground-glass diffusers. We verify the refractive index suppression predicted by Dogariu and Boreman [Opt. Lett.21, 701 (1996)]. We also observe and quantify transmission beyond the critical angle for total internal reflection defined by Snell's law. In particular, these results may be applied to the ANITA experiment, which detects astrophysical neutrino interactions via radio waves produced under the ice. These radio waves must pass through the rough surfaces of the Antarctic ice sheets and shelves.

Surface finish and touch—a case study in a new human factors tribology

This paper is concerned with the sliding contact of a finger tip over rough glass surfaces. It reports measurements of how the roughness affects a person’s feelings caused by the sliding when the person believes the glass to be intended to be used for cosmetics’ packaging. The main purpose has been to gain experience in design of surface touch experiments, self-report data collection and multi-variate statistical analysis of that data, to link subjective outcomes with their physical cause. The paper contains details of these activities. Tests have been carried out with glass surfaces both acid etched and grit blasted, to attain a range of surface roughnesses ( R a) from approximately 1–10 μm. The main conclusion about the feelings caused by sliding is that while a surface is less rough than a finger tip, it generates desirable feelings but when it is rougher than a finger tip it generates undesirable ones (all in the context of what is deemed to be desirable for cosmetics’ packaging).

Kinetics of the thermal polishing of the rough glass surface

A simple mathematical model of thermal polishing of rough glass surface as observed by light beam thermal analysis (LBTA) is presented. The rough surface is represented by a triangular profile used for calculation of the light beam intensity attenuation and an equivalent rectangular profile is used for the modeling of the time course of the thermal polishing. Computational results obtained for the NBS 711 viscosity standard glass showed that the characteristic temperature, obtained from the series of LBTA experiments after extrapolation to zero starting surface roughness, does not represent the glass transition temperature, but it corresponds to the viscosity value of about 109 dPa.s. The validity of the proposed model was confirmed by the comparison of simultaneous LBTA and viscosity measurements of CaO-Y2O3-Al2O3-SiO2 glasses.

The mobility of mercury drops on rough glass surfaces

The horizontal displacement of mercury drops along flat glass surfaces, and how it is affected by roughness, is studied experimentally. The measurements include: static and dynamic drop shapes, advancing and receding contact angles, surface structure characterizations, and the time evolution of the drop's position as a function of mass and surface roughness. The motion is found to be described by a phenomenological model assuming the action of a linear velocity-dependent retarding force with a strength proportional to the liquid-solid contact area. Roughening is found to have the effect of increasing the drops mobility. The contact angle systematics suggest that the latter is due to the formation of a composite liquid-solid interface which reduces the effective contact area. The length of a drop's trajectory is found to be inversely proportional to its effective contact area. A model is proposed which gives a reasonable quantitative understanding of the relationship between contact angles and mobility.