Phase Inversion Temperature Monitoring with Contactless RF Impedancemetry for O/W Emulsion Optimization

International audienceThe phase inversion temperature (PIT) designates the temperature for which a heated emulsion changes from an Oil-in-Water (O/W) state to a Water-in-Oil (W/O) state during a rise in temperature[1]. This important parameter is used to optimize the emulsion stability by finding an optimal storage condition or on the contrary to determine the optimal formulation for oil recovery[2]. The PIT can be affected by three main variables: formulation, composition and protocol[3], and several technics can be used to identify this singular temperature. It is mostly determined by conductometry at a macroscopic scale and it can also be followed by viscosity measurements or endothermic transition determination[4]. In order to optimize the formulation, it is interesting to evaluate the PIT accurately at a mesoscopic scale. Our work aims to identify the PIT and the inner changes taking place in O/W emulsions by monitoring the complex dielectric properties at radiofrequency (RF) range (140 MHz). A contactless RF impedance measuring device developed by the SATIE Laboratory is used[5]. This non-destructive and non-invasive technique allows to measure simultaneously conductivity (σ) and permittivity (ε) evolutions of complex fluids. The first one is directly related to the charge mobility while the second one is related to the polarizability. The ratio between the dissipated and stored energies provides information on the internal structure of the studied environment.The measurement results obtained with our RF impedancemeter are compared with those obtained by low frequency conductivity. The measurements are carried out in parallel between 10 to 90°C for eleven different chosen compositions. This comparison shows phenomena measured respectively at two scales of investigation: mesoscopic and macroscopic. This comparison helps to link the electrical evolutions inside the emulsions. These measurements also enable to monitor the stability of these emulsions over time and to correlate them with the overall structuration of the emulsions. These results were supplemented by additional observations by optical microscopy and ultrasonic rheology.[1]K. Shinoda and H. Arai, “The Effect of Phase Volume on the Phase Inversion Temperature of Emulsions Stabilized with Nonionic Surfactants,” J. Colloid Interface Sci., vol. 25, no. 3, pp. 429–431, 1967, doi: https://doi.org/10.1016/0021-9797(67)90051-3.[2]G. Lemahieu, J. F. Ontiveros, V. Molinier, and J.-M. Aubry, “Using the dynamic Phase Inversion Temperature (PIT) as a fast and effective method to track optimum formulation for Enhanced Oil Recovery,” J. Colloid Interface Sci., vol. 557, pp. 746–756, 2019, doi: https://doi.org/10.1016/j.jcis.2019.09.050.[3]J. L. Salager, “Emulsion Phase Inversion Phenomena,” in Emulsions and Emulsion Stability, 2006, pp. 185–226.[4]V. B. Souza, L. S. Spinelli, G. Gonzalez, and C. R. E. Mansur, “Determination of the phase inversion temperature of orange oil/water emulsions by rheology and microcalorimetry,” Anal. Lett., vol. 42, no. 17, pp. 2864–2878, 2009, doi: 10.1080/00032710903137392.[5]X. Zhou, “Nouveau systeme de controle radiofréquence de micro-algues pour la santé et le bien-être,” Université de Cergy Pontoise, 2016

Bio-Impedance Non-Contact Radiofrequency Sensor for the Characterization of Burn Depth in Organic Tissues

flat circular transmission-line based 300 MHz resonator is implemented for the noncontactassessment of burn depths in biological tissue. Used as a transmit-and-receive sensor, it isplaced here at a 2 mm distance from organic material test samples (pork fillet samples) which havebeen previously heated on one face in various heating conditions involving various temperatures,durations and procedures. Data extracted from the sensor by means of a distant monitoring coilwere found to clearly correlate with the depth of burn observed on the tissue samples (up to 40%sensor output changes for a 7 mm burn depth) and with the heating conditions (around 5% sensoroutput changes for 5.5 mm burn depth obtained at 75 °C or 150 °C). These results open the way tothe development of easy to implement burn assessment and monitoring techniques, which could beintegrated in wearable medical dressing-like monitoring devices

Mesoscopic Monitoring of Human Skin Explants Viscoelastic Properties

The investigation of the mechanical properties of skin is of great interest for monitoring physiological and pathological changes in the cutaneous barrier function for dermatological and cosmetic issues. Skin constitutes a complex tissue because of its multi-layered organisation. From a rheological point of view, it can be considered to be a soft tissue with viscoelastic properties. In order to characterise ex vivo mechanical properties of skin on the mesoscopic scale, a biosensor including a thickness shear mode transducer (TSM) in contact with a skin explant was used. A specific experimental set-up was developed to monitor continuously and in real-time human skin explants, including the dermis and the epidermis. These were kept alive for up to 8 days. Skin viscoelastic evolutions can be quantified with a multi-frequency impedance measurement (from 5 MHz to 45 MHz) combined with a dedicated fractional calculus model. Two relevant parameters for the non-destructive mesoscopic characterisation of skin explants were extracted: the structural parameter αapp and the apparent viscosity ηapp. In this study, the validity of the biosensor, including repeatability and viability, was controlled. A typical signature of the viscoelastic evolutions of the different cutaneous layers was identified. Finally, monitoring was carried out on stripped explants mimicking a weakened barrier function

Lamb wave sensor for viscous fluids characterization

International audienceThis paper is a study of a new sensor for fluid characterization. This sensor is composed of a stainless steel plate in contact with a viscous material. The aim is to characterize the material viscosity by using reflected Lamb waves at the boundary interface. In order to identify the effects on the Lamb reflected modes by the viscous material, a complete study of the propagation wave in the alone plate is first presented. The propagation modes of the loaded plate are then investigated. By monitoring the mechanical impedance, the viscosity of the material in contact is extracted. In order to validate the experimental set-up, the mechanical impedance variation is measured for different water-glycerol mixtures. Results are in good agreement with those obtained by other techniques in the literature

Monitoring of Engineered Stones Used in Artwork Reproductions: Mechanical Characterization by Laser Vibrometry

Many museums have been producing reproductions for several years to replace artworks weakened by outdoor exhibition. Among these, in order to imitate the original aesthetic, the French consortium Réunion des Musées Nationaux–Grand Palais has chosen to work from large-format marble sculpture molds to complex composite materials based on resins comprising mineral fillers. However, similar to the original works of art, these reproductions age and deteriorate due to constant outdoor exposure. For this reason, current research focuses on the preventive conservation and monitoring of the structural health of these reconstructed objects. The goal of this paper was to study the resin/mineral powder composite materials used to produce cultural heritage reproductions of sculptures. This work is oriented toward a comparison of the mechanical properties of composite materials used in the replacement of cultural heritage sculptures (for instance, in the Garden of the Palace of Versailles or the Rodin Museum). The objectives were to first characterize the physical and mechanical properties of these materials in order to identify the most suitable material for cultural heritage reproduction, and secondly, to propose a method with minimal contact that obtained equivalent information as analyses performed with conventional ultrasonic techniques. These nondestructive evaluation techniques could be used for laboratory and in situ analyses. Samples of different polymer/mineral powder filler compositions were analyzed by compressional, shear and surface waves, generated by a 1 MHz center frequency ultrasonic transducer. Firstly, the measurements made it possible to evaluate the velocities of the bulk acoustic waves and extract the Young’s modulus of each tested material. Secondly, in order to have minimal contact with the analyzed structure, a laser interferometry system was used to detect waves at the surface and follow their propagation. The results clearly showed the possibility of using this technique to extract mechanical characteristics of composite materials, allowing for selection of material for the reproduction of large-format statues. For different types of polymer resins, the ability of ultrasonic analysis to track the impact of rock powder (marble or slate) on the mechanical properties of these synthetic materials was clearly observed, proving that this technique holds promise for monitoring the structural health of large-format artwork

Kinetic study of silicon alkoxides gelation by acoustic and rheology investigations

International audienceThe study of the sol to gel transition of silicon based materials obtained from alkoxide precursor Si(OCH3)4, catalyzed by a nucleophilic activator (DiMethylAminoPyridin, DMAP) in methanol has been performed by rheological measurements and sound propagation in an audible range. Different samples obtained by varying the initial monomer concentration, the hydrolysis molar ratio or the temperature have been investigated. An increase of any of these parameters leads to a decrease of the gelation time. Furthermore, the variation of the gelation time versus one of these parameters can be described by power or Arrhenius laws. Therefore the gelation time can be deduced for at least any sol–gel material for which the three parameters lie within the investigated range

Capteurs inductifs radiofréquences pour la caractérisation diélectrique de tissus biologiques

International audienceRadiofrequencies inductive sensors allow non contact characterization of biological tissues to be carried out, by the estimate of the intrinsic dielectric properties of tissues such as the conductivity (σ) and the permittivity (ε). As these properties are related to the physiological or pathological state of the tissue, they can be used as relevant indicators. The paper focuses on a measurement method dedicated to the estimation of these parameters. The proposed method is based on the use of radiating RF surface resonators, used as transmitter and receiver when coupled with a distant probe. Placed at the surface of the media to be evaluated, this type of resonator is sensitive to the modifications of the induced magnetic field, which are sensed through the impedance changes of the resonator. The sensitivity to the dielectric parameters of such sensors are evaluated on tissue phantoms made of saline agarose gels

Conserver l’instrument de musique en état de jeu : contraintes d’origine et origines des contraintes mécaniques au sein de l’instrument de musique à cordes

Quel est l’état mécanique d’un objet conservé dans les collections patrimoniales ? Cet état mécanique est-il compatible avec la valeur d’usage que les musées d’instruments de musique ont pour mission de conserver ? Afin de garantir des modalités déontologiques de conservation des instruments de musique à cordes, une plateforme numérique d’aide à la décision du maintien en état de jeu pour les instruments à cordes est en cours de conception. Prenant en compte l’état matériel de la structure et les différents efforts qui s’appliquent sur l’instrument de musique, l’approche mécanique développée, qui exploite les outils les plus récents de cette discipline, permet d’évaluer les paramètres qui influencent le plus le comportement dynamique de l’instrument, et avec quel niveau de méconnaissance des paramètres d’entrée le pronostic de remise en état de jeu demeure valable. Les modèles mécaniques présentés apportent des réponses quantifiées en termes de risque d’endommagement de l’œuvre maintenue en état de jeu et mettent en évidence que les états de contrainte induits par les gestes de fabrication initiaux doivent être pris en compte et peuvent conditionner la potentialité musicale des instruments.What is the mechanical condition of an object kept in heritage collections? Is this mechanical condition compatible with the use value which museums of musical instruments have a mission to maintain? So as to guarantee a deontological approach to the conservation of string musical instruments, a digital helpline for maintaining string instruments in playing condition is being designed. Taking into account the physical condition of the structure and related operational stress, the adopted mechanical approach, which uses this discipline’s most recent tools, enables us to assess the parameters affecting the instrument’s dynamic behaviour the most, and with what level of ignorance of input parameters the prognostic for restoring the instrument to functioning condition remains valid. The mechanical models presented here provide quantified answers in terms of risk of damaging the instrument maintained in playing condition and highlight the fact that original fabrication constraints must be taken into account and may determine the musical potential of the instruments

Ultrasonic microrheology for ex vivo skin explants monitoring: A proof of concept

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