Study on skin roughness caused by surfactants: II. Correlation between protein denaturation and skin roughness

An attempt to determine protein denaturing potency of typical surfactants has been made by measuring specific rotation of bovine serum albumin. The potencies obtained were examined in relation to the intensities of skin roughness in vivo caused by the surfactants, and a noticeable correlation was found between them. This fact also suggested that the cause of skin roughness may be attributed to a certain extent to adsorption of surfactants. In addition, this technique is very useful in predicting the skin roughening potency of a surfactant without using human skin.     

Effect of polyoxyethylated materials on the interaction of surfactants with skin

The effect of surfactants on skin has been investigated by means of two experimental techniques, viz., by permeability studies using isolated neonatal rat stratum corneum membranes, and by studies on the reduction of the electrophysiological potential across freshly excised frog skin membranes. Permeability studies indicate that typical cationic and nonionic surfactants are weak penetrants, unlike anionic surfactants, as exemplified by sodium lauryl sulfate (SLS), which readily penetrates and tends to destroy the integrity of stratum corneum membranes in a matter of hours. The addition of polyethylene glycols (PEG) or nonionic surfactants to solutions of SLS results in a considerable reduction in the last mentioned effects, the reduction tending to increase as the molecular weight and ethylene oxide content of the additive increase. By contrast with permeability, the electrophysiological measurements show that cationic surfactants can be extremely active: the typical surfactant, cetyltrimethyl ammonium bromide (CTAB), at a level of 0.5% in Ringer solution, destroys the potential across frog skin in minutes, and, indeed, is comparable in this respect to SLS. Nonionic surfactants are comparatively inactive, and factant reduces the effect of the latter significantly. Preapplication of a solution of PEG to the membrane, rather than incorporation in the solution of the surfactant, affords better protection against the latter as judged by both permeability and potential criteria.     

Lipid/surfactant compounds as a new tool to optimize skin-care properties of personal-cleansing products

Surfactants are commonly used in personal-care products to increase cleansing performance and to create pleasing foam. However, surfactants can also damage the skin by removing skin lipids and causing corneocytes to swell, resulting in increased skin roughness and transepidermal water loss. Newly established methods help to quantify these effects in controlled consumer studies. In addition, in vitro experiments with skin cell cultures show the potential inflammatory action of surfactants, which in the in vivo situation may provoke skin irritation. These detrimental effects are even enhanced by frequent treatment with surfactant-based personal-care products. Together with the use of mild surfactant combinations, the addition of surfactant-compatible lipid compounds has proved a convenient way of not only counteracting the negative side effects of surfactants but also exerting positive skin effects. In a controlled consumer study, analysis of skin lipids after skin cleansing revealed the lipid-layer strengthening efficacy of lipid/surfactant mixtures that can be solubilized in the personal-care formulation or disperses as waxy particles. As a result, skin roughness after cleansing treatment, as measured by fast optical in vivo topometry of the skin, is improved, and consumers perceive that their skin is smooth and cared for.     

Skin-customized wearable device adhesive without skin damage

Wearable medical devices are gaining popularity owing to their potential for seamless integration with the human body and long-term monitoring of physiological activity. However, conventional adhesives were developed based on the assumption of healthy adult skin and may not account for variations in skin characteristics across different species, environments, and body parts. Consequently, the adhesive strength of wearable devices may significantly differ depending on the skin surface to which they are attached, potentially causing skin damage. In this study, we developed a customized wearable-device adhesive without skin damage by analyzing the characteristics of the skin surface based on oil and water content and roughness according to different species and parts. Our findings demonstrated that increased root-mean-square roughness of the skin surface led to reduced contact area and decreased adhesion force between the polydimethylsiloxane (PDMS) pad and skin surface. Surprisingly, hairless skin exhibited 1.5 times higher adhesion strength than hairy skin due to stronger molecular forces resulting from the higher surface energy of the skin. Additionally, the hole-patterned PDMS pad on sweaty skin displayed improved adhesion properties compared to the cylinder-patterned PDMS pad. Therefore, customized wearable adhesives provide an effective strategy for developing skin-damage-free wearable devices.     

The effect of substrate roughness on tape peeling

This study explores the effect of substrate roughness on peel force for tape peeling. In order to assess the effect of substrate roughness on peel force for tape peeling, a new approach based on a peel zone model was established, including rough surfaces as substrate. This approach is applicable for rough surfaces and accomplished by using contact and adhesion theories. Experimental values were used to calculate peel forces for surfaces with a different level of roughness. The results indicated that the peel force for a rough substrate for the same peel angle is smaller than the one for a flat substrate and that increasing root mean square roughness decreases the peel force. This study is a different approach to prove conclusions that may be proved with experiments by using real animals such as Gecko, lizard, etc. Also, this theory is useful for explaining how some animals such as Gecko peels-off from rough surfaces more easily and quickly than from smooth ones.     

皮肤清洁剂综述(续前)

９乳液类皮肤清洁剂在一篇汉高公司的专利中报道了许多乳液状的水溶性皮肤清洁剂 ,一个明显的例子包含油和烷基或链烯基低聚葡糖苷甘油醚。据报道 ,该产品对皮肤温和无刺激性 ,一般用于眼部和敏感皮肤的清洁 ,其参考配方如下。温和皮肤清洁剂ｗ（组分）／ %甘油基十六烷基葡糖苷５ ００聚甘油酯 -３ -二异硬脂酸酯４ ００甘油油酸酯２ ００蜂蜡３ ００乙醚二辛酯５ ００辛基十二烷醇８ ００椰油三辛酸／癸酸酯５ ００甘油５ ００硫酸镁１ ００水加至１００１０喱类清洁剂Ｔｈ．Ｇｏｌｄｓｃｈｍｉｄｔ描述了用温和的酰胺丙基甜菜碱表面活…     

Toughness and roughness in hybrid nanocomposites of an epoxy matrix

The present paper investigates the relationship between roughness and toughening mechanisms in hybrid epoxy nanocomposites with carbon nanotubes (CNT) and graphene nanoplatelets (GNPs). The role of adding a block copolymer (BC) to the studied systems was also investigated. The nanocomposites were prepared by means of high‐energy sonication and in situ polymerization. All nanocomposites presented higher numerical values for K_Ic than untoughened systems. The system containing 0.5 wt% of CNTs presented an increase of 35% in K_Ic compared to neat epoxy, and the hybrid nanocomposite, at the proportion of 1:1 (CNT:GNP), with 0.5 wt% total of nanoparticles and also containing 0.5 wt% of BC, had an increase of 34% compared to the neat epoxy. Systems with higher amounts of graphene showed the highest roughness values, having crack deflection/exfoliation between the GNP layers as the main toughening mechanism. On the other hand, systems with more CNTs presented a lower fracture surface roughness, and the main toughening mechanism was bridging/break‐up of the nanotubes. Hybrid systems have more types of mechanisms than simple ones. With only one type of nanoparticle, however, some of those mechanisms are not effective in increasing the toughness, only increasing the fracture surface roughness. POLYM. ENG. SCI., 59:1258–1269 2019. © 2019 Society of Plastics Engineers     

Surface roughness criteria for cement paste nanoindentation

Analysis of nanoindentation experiments assumes that the indentation occurs on a flat surface. As a result, the accuracy of nanoindentation depends on reducing the surface roughness to a tolerable level. Within the context of statistical nanoindentation techniques suitable for heterogeneous materials, this study presents a criterion for roughness of cement paste surfaces for nanoindentation, and describes a method for obtaining the desired roughness. Through a systematic experimental study, we show the evolution of roughness and nanomechanical properties from indentation as a function of increased polishing. We conclude that the root-mean-squared (RMS) roughness of the sample, taken over a square area with edge dimensions of 200 times the average indentation depth of the dominating phase of the material, should be less than five times the average indentation depth of the dominating phase of the material.     

表面活性剂与皮肤的相互作用研究

综述了洗涤剂的起源及发展、表面活性剂对皮肤的损伤以及为了降低这些伤害在配方设计上所做的一些改变,并对洗涤剂向温和性发展做出了展望。     

Effect of polishing method on surface roughness and bacterial adhesion of zirconia-porcelain veneer

The purpose of this study was to evaluate the effect of various polishing methods on surface roughness of zirconia-porcelain veneer and to correlate the findings with early bacterial adhesion. The study specimens were glazed (control group), glazed after fine polishing (glazed group) and polished with Exa Cerapol (Cerapol group) or with Shofu porcelain adjustment kit (Shofu group) (n =20). Surface roughness was then measured using profilometer and scanning electron microscope (SEM). After artificial saliva coating, the specimens were incubated in Streptococcus mitis suspension for 4 h at 37 °C. Adherent bacteria were quantified from SEM images. Streptococcal viability was assessed by LIVE/DEAD staining kit and fluorescent microscope. There were significant differences in surface roughness according to polishing method and surface material. Relatively smoother surfaces were found in zirconia surfaces and glazed porcelain surfaces. There were also significant differences in bacterial adhesion according to polishing method and surface material. Cerapol group showed minimal bacterial adhesion with more dead cells when compared to other groups. A positive correlation between surface roughness and bacterial adhesion was found in glazed porcelain surface and a negative correlation in zirconia surface of Cerapol group, both with no statistical significance. Within the limitations of in vitro study, surface roughness and bacteria adhesion were significantly influenced by polishing method and surface material. Also, there was a positive correlation and negative correlation between surface roughness and bacterial adhesion in glazed porcelain surface and in zirconia surface of Cerapol group, respectively.     

Surface roughness of AlN films deposited on negatively biased silicon and diamond substrates

Our previous studies on AlN microstructures have shown that smooth amorphous films (a-AlN) can be grown on negatively biased Si substrates by the versatile physical vapour deposition technique under reactive magnetron sputtering. These a-AlN films are produced by energetic Ar ion bombardment under negative bias whereas those grown without bias were columnar crystallized ones (c-AlN). Here, we show first that depositing an a-AlN layer on c-AlN/Si structures by switching a suitable bias to the Si substrate can efficiently reduce their surface roughness. We then extend this smoothening method to a c-AlN/Poly-crystallized diamond (PCD) structure to reduce its high surface roughness that hampers using such structures in SAW device design. In fact, the piezoelectric c-AlN surfaces grown on rough diamond surfaces are equally rough. Effectively, the a-AlN layer deposited on the c-AlN/PCD structure brings down the latter's RMS surface roughness to one tenth of its initial RMS roughness, as confirmed here by TEM and AFM observations. The insulating property of the diamond as biased substrate doesn't impede the growth of this a-AlN layer. This smoothening method is without process interruption, where simply a negative bias is switched on to the diamond substrate once the desired piezoelectric c-AlN film thickness as monitored here by in-situ reflectometry, is attained. This as-grown smoothening method can be therefore easily and rapidly implemented and can thus replace time-consuming and costly PCD ionic and/or mechanical polishing. Hopefully, the method can be advantageously applied to c-AlN/nano-crystallized diamond structures (NCD) where the NCD films are not prepared under rigorous conditions meant to minimize their surface roughness.     

The performance of surfactant on the surface characteristics of electroless nickel coating on magnesium alloy

Magnesium and its alloys corrode rapidly in the electrolyte bath. Surfactants while used extensively as surface active agents in the electrolyte bath, have been little studied on magnesium surfaces. The influence of surfactants cetyltrimethyl ammonium bromide (CTAB) and sodium lauryl sulfate (SLS) on the surface properties such as roughness, morphology and topography of electroless Ni–P deposits on magnesium alloy was researched. The research reveals that the surfactant solutions has significant influence on the composition of coating, surface roughness and surface morphology. In addition, it has marginal effect on the microhardness. Electroless coatings with addition of surfactants produce a smooth surface and average roughness value of 1.412 μm for CTAB and 1.789 μm for SLS, which are less than the value (2.98 μm) without surfactant addition. There was a significant improvement in the rate of deposition. However, the surfactants influence reached maximum at critical micelle concentration and above this value it gets stabilized. The initial structure appears to be dependent upon the percent occluded surfactants. The surface microstructures are discussed in line with the experimental observations.     

Surface roughness effects onmicroparticle adhesion

A new self-consistent model is developed to treat the static contact of a microparticle with a flat barrier in the presence of molecular adhesion and surface roughness. Separation between their mean datum planes is modeled considering the elastic deformation of the microparticle and surface. The contact pressure is computed from the Lennard-Jones law following the Derjaguin approximation. The elastic deflection of the mean datum plane is calculated from the effective pressure by the half-space elastic theory. Roughness is modeled by introducing a Gaussian distribution to the gap between the surfaces. An effective pressure is defined as the statistical average of the contact pressure over the roughness heights. A solution satisfying all of the above conditions gives a self-consistent method of modeling adhesion between the microparticle and the flat barrier. Using collocation methods the equations are discretized as a large system of nonlinear algebraic equations. A continuation method is used to find the multiple numerical solutions for the mean separation and the effective contact pressure. Finally, adhesive contacts of both smooth and rough surfaces are simulated in a comparative manner to elucidate the features of surface roughness in the presence of molecular adhesion. The standard deviation of the Gaussian distribution is used as a parameter to assess the effects of roughness on the pull-off force. It is shown that increasing surface roughness significantly reduces the pull-off force and decreases the tendency for the microsphere to snap-on and snap-off.     

Synthesis and Characterization of Novel Surfactants based on 2-Hydroxy-4-(Methylthio)Butanoic Acid Part 3: Microemulsions from Nonionic Sulfoxide Ester Surfactants

In this work, ester sulfoxide (ESO) surfactants based on 2-hydroxy-4-(methylthio) butyric acid are shown to have temperature-sensitive microemulsion phase behaviors. Both C10 (C₁₀ESO) and C12 (C₁₂ESO) surfactants studied contained one sulfoxide unit in the structure. Phase inversion temperatures (PIT) and interfacial tensions (IFT) between water-rich and oil-rich phases have been measured for ternary systems of water, oil, and sulfoxide surfactants. Hydrophilic–lipophilic deviation (HLD) parameters of these surfactants were obtained by fitting the experimental data to a semiempirical HLD equation. The characteristic surfactant parameter and temperature sensitivity of C₁₀ESO and C₁₂ESO surfactants were obtained and compared with similar ethoxylated alcohol surfactants. By comparing the characteristic parameters of these surfactants with those of ethoxylated alcohol surfactants, it was shown that one sulfoxide ester moiety is equally hydrophilic as approximately 5 ethylene oxide groups. The temperature sensitivity of the ESO was roughly a factor of four less than ethoxylated surfactants based on the temperature coefficient of the HLD equation.     

A second-order moment particle-wall collision model accounting for the wall roughness

A particle-wall collision model accounting for the wall roughness in the framework of second-order moment two-phase turbulence models is proposed, combining the advantages of the collision approach in the particle trajectory model and the PDF approach in the two-fluid model. The proposed model is incorporated into the second-order moment two-phase turbulence model to simulate axi-symmetric swirling and mixing-layer gas-particle flows. The simulation of swirling gas-particle flows and its comparison with the measurements show that the proposed model gives much better results than the widely used zero-gradient condition does, and is suggested to be used as wall boundary condition for particle phase instead of the widely used one. The simulation of mixing-layer gas-particle flows shows that the model accounting for the wall roughness gives smaller longitudinal mean velocities and greater longitudinal fluctuation velocities for particles, which are in better agreement with the experiment results, than those obtained using the model not accounting for the wall roughness. The results are qualitatively consistent with the simulation results using the particle trajectory model.     

Surface roughness analysis of electrodeposited Cu

Cu films were electrodeposited with mass transport controlled using a rotating disc electrode (RDE), and imaged with an atomic force microscope (AFM). The length-dependent roughness w(l,t) of these films follows a power law of the form w∝lHtβloc for small length-scales l, with the local roughness exponent, β_loc, varying from 0 to 0.5 depending on the experimental conditions. It was found that contrary to previous work β_loc is not simply a function of the ratio of the current j to its diffusion-limited value j_L. Focused ion beam (FIB) imaging was used as a new method of characterizing the film roughness. FIB images confirmed the existence of small β_loc values for films for which the AFM data could have been unreliable. FIB is a particularly powerful method for characterizing high roughness films.     

Effects of roughness elements on laminar flow and heat transfer in microchannels

A model of laminar flow and heat transfer in rough microchannels is developed and analyzed numerically to compare the effect of roughness elements on the thermal and hydrodynamic characteristics. In this model, the rough surfaces are configured with triangular, rectangular and semicircular roughness elements, respectively. Here, the effects of the Reynolds number, roughness height, and roughness element spacing on pressure drop and heat transfer in rough microchannels are all investigated and discussed. The results indicate that the global heat transfer performance is improved by the roughness elements at the expense of pressure head when compared to the smooth channel. Differing from the smooth microchannels, both the Poiseuille number and average Nusselt number of rough microchannels are no longer constant with Reynolds numbers and are larger than the classical value. Especially, the difference from the effects of three types of roughness elements is identified. With the increasing roughness height, the flow over surfaces with semicircular and triangular roughness elements induces stronger recirculation and flow separation. This contributes to heat transfer enhancement but also increases the pressure drop. However, the influence of the rectangular roughness element height is weaker than that of semicircular and triangular elements. In addition, the effects of the spacing of roughness elements on the Poiseuille number and average Nusselt number are in decreasing order for semicircular, triangular and rectangular roughness elements, respectively.     

Surface activity and cutaneous effects of monoalkyl phosphate surfactants

Monoalkyl phosphates of high purity were synthesized and were investigated for their surface-active properties and cutaneous effects. It has been found that these surfactants possess adequate surface-active properties similar to those of common anionic surfactants and that they exhibit considerable safety on the skin in comparison with typical anionic surfactants used commercially.     

阴/阳离子表面活性剂复配微乳液体系的ε-β“鱼状”相图研究

用ε-β“鱼状”相图法研究了离子液体表面活性剂溴化1-十二烷基-3-甲基咪唑（C12mimBr）与十二烷基硫酸钠（SDS）复配形成的SDS-C12mimBr/正丁醇/正辛烷/5%NaCl水溶液微乳液体系的相行为和增溶性能。阴、阳离子表面活性剂以不等摩尔比复配,由于强烈的静电作用,产生显著的协同作用,使复配体系的增溶性能比单一表面活性剂得到了显著的提高。     

Methods for determining the distribution of bacteria in the skin

Five methods used to study bacteria in the skin are reviewed: swabbing, scrubbing, or scraping; biopsy; impression plate; adhesive stripping; and air-sampling for bacteria-shedders. Scraping and swabbing methods give only a rough idea of the numbers and kinds of bacteria on a given area of skin. More recent adaptations of these techniques have introduced the use of soaps or surfactants to disperse the bacteria, followed by quantitative plate counts on serial dilutions. Biopsy methods are little used because they give only qualitative results and are traumatic to the experimental subject. Impression plates give low counts in most cases and enumerate only those bacteria which are lying on the surface layer of thestratum corneum. Adhesive stripping methods are the only ones which give a precise determination of the distribution of colonies of bacteria with regard to both area and depth in thestratum corneum. Counts run much higher than impression plates.