Dry Coupling Ultrasonic High Frequency (10-100 MHz) Sensors for Detection of Surface and Tribological Properties at a Submicrometric Scale

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Wide-range viscoelastic measurement using resonating sensors

International audienceWe have developed a specially designed sensor with its associated instrumentation using a so called acoustical near-field technique based on small resonating horns. Contrary to the conventional measuring devices used in the rheology industry, this sensor enables wide-range and continuous viscosity measurements, including liquid to solid material transition. The sensor is composed of a small piezoelectric element which enables the horn to resonate. Shear waves are generated by means of the thinner part of the sensor (dipped into the material) confining the acoustic field to the tip to ensure local measurements. The frequency is scanned across the resonating frequencies in order to perform these measurements with the maximum of speed and efficiency. The shear moduli G′ and G′′ of the material is deduced from the electrical impedance measurement at the resonance frequencies. In case of rapidly changing materials, such as quick setting cements or polyesters, we have developed a specific fast instrumentation based on the impulse response of the sensor, which realizes very fast measurements, typically 30 measurements per second. Modelization and experiments are reported

Characterization of New Titanium Oxide Polymer Hybrid Membranes for Biofilm Formation

International audiencePresently, there is great need to create new matrices for diverse applications particularly in the fields of biotechnology and food industry. Here, we report on the synthesis of new matrices based on a mixture of polymer cellulose acetate butyrate/copolymer polyacrylonitrile acrylamide/TiO2. The characterization of the new matrices was performed using IR spectroscopy, QCM technology, and SEM. The tests revealed that when we use our polymers as carriers, there is a limit for the concentration of titanium of 5%. Further increasing of Ti concentration leads to precipitation processes. The QCM analyses show that a low concentration of Ti(OBu)4 does not influence the viscosity of the matrices obtained, but their elasticity changes significantly. The membranes obtained were successfully applied for biofilm formation of Yeast strain Saccharomyces cerevisiae

Gelation monitoring by quartz microbalance in pulse mode

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Kinetic reaction monitoring of acidified milk gels with a quartz resonator : effect of temperature and gdl quantities

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Lamb mode reflections at the end of a plate loaded by a viscoelastic material

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Synthesis Of New Polymer Matrices Including Amino Acids

International audienceCurrently the application of biomolecules such as amino acids, carbohydrates and nucleic acids in the diagnostic and treatment (drug delivery) of wide number of diseases turned on the effort of many scientific groups on their encapsulation[ ]. The matrices based on different organic or/and inorganic materials were used. Significant problems arise due to multifunctionality of these molecules. The choice of polymer matrix as well as suitable approach for first amino acid bonding plays a crucial role of biomolecule incorporation process. The sol-gel technology is a modern technique to obtain hybrid polymer matrices. It is based on the hydrolysis of starting materials and further polycondensation process. The strictly control of these processes plays key role for the properties of final materials as well as the protection against precipitates formation. Herein we report for several strategies for amino acid incorporation in organic and/or inorganic polymers. Different type of amino acids (either with different pKa or spatial obstructed group) is linked in order to study the structure of the final material. The rheological properties (elasticity and viscosity) of these matrices are studied by means of an ultrasonic technique developed in our laboratory. The experimental results of the G' and G" moduli for different condition of elaboration is used to access to the microstructure evolution [ ]. Some advantages and defaults due to type of amino acid protection as well as solvent systems used for polymerization process will be discussed. The obtained matrices will be further used for biosensors and bioreactors design

Rheological monitoring of tau protein polymerisation with acoustic waves sensor

International audienceAmong acoustic waves sensors, the thickness shear mode resonator presents high sensitivity for the measurement of liquid viscoelastic properties, enabling the monitoring of the shear moduli, G′ G″, by using a suitable physical model. The development of an instrumental system for detecting the tau protein involved in Alzheimer's disease is proposed which will aid in understanding the mechanisms of this disease. The tau protein is present in complex products such as blood and cerebrospinal fluid. The experimental results show that the acoustic wave system allows to differentiate between tau protein solutions with different states of polymerisation