Evaluation of the surface properties of hair with acoustic emission analysis.

OBJECTIVE: The tactile sensation of hair is an important consumer-perceivable attribute. There are limited instrumental options to measure the haptic properties of hair. In this study, we introduce a novel technique using the acoustic emissions produced when skin comes in contact with dry hair in a stroking motion. METHODS: Using a free-field microphone with a frequency response of 8-12,500 Hz, we recorded acoustic emission data of the interaction of skin with hair. Data were captured with Electroacoustics Toolbox software and analysed with Matlab. Acoustic emission profiles were generated allowing us to monitor the acoustic response at distinct frequencies. RESULTS: Various experiments were conducted to develop this novel technique as a suitable measure to monitor the surface properties of hair. Increasing the normal force and velocity of the interaction led to an increase in acoustic emissions. We also examined the acoustic profile of hair that underwent chemical treatment. For example, bleached hair produced a much higher magnitude acoustic response than the corresponding virgin hair. On the other hand, hair conditioner systems mitigated the acoustic response. Finally, investigations of textured hair revealed that the three-dimensional structure of the hair fibre assembly and its ability to return to its original state when perturbed produce the most dominant acoustic response for this type of hair. CONCLUSION: We introduce a cutting-edge method to reproducibly evaluate the surface properties of hair. Different types of hair geometry produce unique acoustic profiles as do hair types that experience harsh damaging treatments. This is also a very practical and efficient way to evaluate the degree of protection or conditioning of the fibre.

OBJECTIF: La sensation tactile des cheveux est un attribut important perceptible par le consommateur. Il existe des options instrumentales limitées pour mesurer les propriétés haptiques des cheveux. Dans cette étude, nous introduisons une nouvelle technique utilisant les émissions acoustiques produites lorsque la peau entre en contact avec les cheveux secs dans un mouvement de caresses. MÉTHODES: En utilisant un microphone champ libre avec une réponse en fréquence de 8 à 12 500 Hz, nous avons enregistré des données d'émission acoustique de l'interaction de la peau avec les cheveux. Les données ont été capturées avec le logiciel Electroacoustics Toolbox et analysées avec Matlab. Nous avons généré des profils d'émission acoustique. De cette manière nous pourrions surveiller la réponse acoustique à des fréquences distinctes. RÉSULTATS: Nous avons fait diverses expériences pour développer cette nouvelle technique comme mesure appropriée pour surveiller les propriétés de surface des cheveux. L'augmentation de la force normale et de la vitesse de l'interaction entre la peau et les cheveux ont causé une augmentation des émissions acoustiques. Nous avons également examiné le profil acoustique des cheveux ayant subi un traitement chimique. Par exemple, les cheveux décolorés ont produit une réponse acoustique de beaucoup plus grande amplitude que les cheveux vierges correspondants. D'autre part, les systèmes d'après shampooing ont atténué la réponse acoustique. Enfin, des investigations sur des cheveux texturés ont révélé que la structure tridimensionnelle de l'ensemble de fibres capillaires et sa capacité à revenir à son état d'origine lorsqu'il est perturbé produisent la réponse acoustique la plus dominante pour ce type de cheveux. CONCLUSION: Nous introduisons une méthode de pointe pour évaluer de manière reproductible les propriétés de surface des cheveux. Différents types de géométrie de cheveux produisent des profils acoustiques uniques, tout comme les types de cheveux qui subissent des traitements agressifs. C'est également une manière très pratique et efficace d'évaluer le degré de protection ou de conditionnement des cheveux.

Rheological fingerprinting as an effective tool to guide development of personal care formulations.

OBJECTIVE: Conventional rheological techniques in the linear viscoelastic region provide insights about the spatial configuration of the microstructural components of personal care formulations in their 'at-rest' state. However, they fail to describe the textural experience associated with large and fast deformations during daily consumer application. In this study we present a non-conventional rheological technique-large amplitude oscillatory shear (LAOS)-for probing the transformation of a material during its application. This technique is proposed a practical tool for formulators in their efforts to design products with desired textural attributes. METHODS: A non-linear rheological technique termed LAOS was utilized to capture the textural expression perceived by consumers. Lissajous plots (stress vs. strain or strain rate) provide a fingerprint of the formula and are utilized to both analyse the thickening mechanism and monitor the influence of various parameters, such as the chemistry, molecular properties, colloidal parameters and processing conditions. RESULTS: In this study, we showcased several approaches for modifying the texture of personal care formulations and show the influence of various parameters on the characteristics of the Lissajous curves and their relation to sensorial perception. This fingerprinting technique shows that increasing the molecular weight or hydrophobic modification boosts the elasticity and thickening efficiency of a given polymer. Differences in the chemistry of rheological ingredients also influence the characteristic Lissajous fingerprint. In high concentration surfactant systems, which tend to form worm-like micelles, their unique Lissajous fingerprints indicate structure rebuild because of fast kinetics at large but slow deformations. Analysis of lamellar gel-based hair conditioner formulations demonstrates the unique high yield stress of these types of materials, accompanied by the fast breakdown transition from a solid to viscous structure because of their crystalline lamellar gel structure. CONCLUSION: The LAOS technique presented in this article is intended to better capture the textural expression perceived by consumers. Lissajous plots-generated from the LAOS experimental data-provide a fingerprint of the tested formula and are utilized to both analyse the thickening mechanism and monitor the influence of various parameters, such as the chemistry and molecular weight of the thickener, pH of the formula medium and influence of other ingredients in the formula (surfactants, emulsifiers, etc.).

OBJECTIF: Les techniques rhéologiques conventionnelles dans la région viscoélastique linéaire fournissent des informations sur la configuration spatiale des composants microstructurels des formulations de produits cosmétiques dans leur état « au repos ¼. Mais elles ne décrivent pas l'expérience de texture associée à des déformations importantes et rapides lors de l'application quotidienne par les consommateurs. Dans cette étude, nous présentons une technique rhéologique non conventionnelle, le cisaillement oscillatoire à grande amplitude (Large Amplitude Oscillatory Shear, LAOS), pour examiner la transformation d'un matériau pendant son application. Cette technique est proposée comme outil pratique pour aider les formulateurs dans leurs efforts pour concevoir des produits qui ont les attributs texturaux désirés. MÉTHODES: Une technique rhéologique non linéaire appelée LAOS a été utilisée pour capturer le style textural perçu par les consommateurs. Les courbes de Lissajous (stress vs contrainte ou taux de déformation) fournissent une empreinte de la formule et sont utilisées pour analyser le comportement épaississant et surveiller l'influence de divers paramètres, tels que les propriétés moléculaires et chimiques, les paramètres colloïdaux et les conditions de traitement. RÉSULTATS: Dans cette étude, nous avons présenté plusieurs approches pour modifier la texture des formulations cosmétiques et montrer l'influence de divers paramètres sur les caractéristiques des courbes de Lissajous et leur relation avec la perception sensorielle. Cette technique d'empreintes montre que l'augmentation du poids moléculaire ou la modification hydrophobe stimule l'élasticité et l'épaississement d'un polymère donné. Les différences dans la chimie des ingrédients rhéologiques influencent également l'empreinte caractéristique de Lissajous. Dans les systèmes de tensioactifs à haute concentration, qui ont tendance à former des micelles semblables à des vers, leurs empreintes Lissajous uniques indiquent une reconstruction de la structure à cause de cinétiques rapides dans leur ensemble mais des déformations lentes. L'analyse des des formulations lamellaires d'après-shampooing à base de gel démontre le stress unique à haut rendement de ces types de matériaux, accompagnés par la transition de répartition rapide d'une structure solide à visqueuse à cause de leur structure lamellaire cristalline. CONCLUSION: La technique LAOS présentée dans cet article vise à mieux appréhender le style de texture perçu par les consommateurs. Les graphiques de Lissajous, générées à partir de données LAOS expérimentales, fournissent une empreinte de la formule testée et sont utilisés pour analyser le mécanisme épaississant et surveiller l'influence de divers paramètres, tels que la chimie et le poids moléculaire de l'épaississant, le Ph moyen et l'influence des autres ingrédients (tensioactifs, émulsifiants, etc.) dans la formule.

Spectrofluorescence of skin and hair.

There are numerous chromophores present throughout the strata of human skin, which present many challenges and opportunities to probe molecular events. Fluorescence spectroscopy is principally employed to identify important biochemical components of the skin including endogenous tryptophan, tyrosine, pepsin-digestible collagen cross-links, collagenase-digestible collagen cross-links, NADH, etc. Over the last 15 years, many advances in instrument technology have been introduced allowing for much faster data acquisition with spectrofluorometers. As a result, a series of spectrofluorescence emission scans can be generated for a range of excitation wavelengths, or vice versa (excitation scans for a range of emission wavelengths), quickly to generate excitation-emission matrices. In this work, we constructed an endogenous fingerprint of fluorescent compounds present in skin, hair and nail tissues by employing a range of excitation wavelengths from 270 to 450 nm with a resolution of 2 nm. As a result, we generated surface plots of fluorescence emission as a function of excitation and emission wavelengths. From these data, we identified the predominant fluorescent chromophores in each tissue. We examined several sources of skin including in vivo human and ex vivo pig, sheep, goat and cow skin. We also analysed various types of mature hair characterized by the degree of melanin content. These analyses provided us with a fundamental understanding of the effects of melanin distribution in hair fibres and aided with the identification of fluorophores present in hair.

Image analysis to quantify histological and immunofluorescent staining of ex vivo skin and skin cell cultures.

Image processing steps and analysis techniques were developed for the quantification of photomicrographs obtained from light and fluorescence microscopy. The substrates examined were either skin cell cultures, such as normal human keratinocytes (NHK) or fibroblasts, or ex vivo skin sections. Examples of the analyses are provided for the comparison of skincare active ingredient treated samples vs. placebo to demonstrate the utility of the methods to quantify and provide numerical data for a procedure that is typically qualitative in nature and based on observations by a histologist. Quantifiable experiments that are discussed include: Fontana Masson staining for melanin expression; Nile red staining to detect cellular lipid droplets; nuclei staining with diamidino-phenylindole (DAPI); and immunofluorescent staining of protein expression with a primary antibody directed against the protein (antigen) and a secondary antibody tagged with a fluorescent dye (Alexa Fluor 488) against the primary antibody.

Investigation of human hair fibers using lateral force microscopy.

Atomic force microscopy (AFM) and lateral force microscopy (LFM) were used to investigate the morphologic and surface changes associated with various surface modifications to human hair. These included extraction with a series of solvents, bleaching, and treatment with a cationic copolymer. The study assessed the ability of these techniques to distinguish the changes in surface properties, including morphology and friction coefficient, as manifested in changes brought about by the indicated surface modifications. While topographic morphology can easily be investigated with contact AFM. LFM offers an additional tool for probing the surface distribution of oils and waxes. The removal of surface lipids from the fiber surface was accomplished using soxhlet extraction with t-butanol and n-hexane, while the free internal lipids (within the fiber structure) were removed by extraction with a mixture of chloroform and methanol (70:30, v/v). In addition, the surface of hair was modified with the cationic polymer, co(vinyl pyrrolidone-methacrylamidopropyl trimethylammonium chloride [PVP/MAPTAC]), and its distribution on the surface was monitored. Ambient AFM and LFM studies of surface modified and native fibers clearly indicate that when investigated as a function of tip loading force, the different modifications result in changes of the friction coefficient, which increase in this order: native, bleached, solvent extracted, and polymer-treated hair. Friction images show surface variations that are interpreted as areas of varying lipid film coverage. In addition, topographic images of the fibers show the presence of small pores, which become increasingly prevalent upon solvent extraction.