Virginie Blondeau-Patissier

Doping properties of PEDOT films electrosynthesized under high frequency ultrasound irradiation.

The present study presents the use of high frequency ultrasound (500 kHz, 25 W) for 3,4-ethylenedioxythiophene (EDOT) electropolymerization in aqueous medium in order to investigate its effects on conducting polymer properties. It was shown that mass transfer increases under ultrasound irradiation which improved electropolymerization and the comparison with experiments carried out at the same mass transfer level (4.6 × 10(-5) ms(-1)) puts in evidence that stirring effect is not the only phenomenon induced by ultrasound during electrodeposition. PEDOT films elaborated under ultrasonication present increased doping levels revealed by X-ray Photoelectron Spectroscopy (XPS) analysis, especially in the case of thick films (measured by mechanical probe), thanks to better incorporation of counter ions within polymer matrix as another consequence of mass transport improvement under ultrasound and probably film heating by wave absorption for the highest thicknesses. A dilation of the film under sonication leading to an increase in film thickness was also highlighted. Finally, a refining of the surface structure was also observed via SEM imaging.

Electrosynthesis and characterization of conducting polypyrrole elaborated under high frequency ultrasound irradiation

The effects of high frequency ultrasound (500kHz) on pyrrole electropolymerization in sodium perchlorate aqueous medium have been investigated. Cyclic voltametry studies showed that there is no influence on pyrrole oxidation potential. Scanning Electron Microscopy (SEM) imaging, and mechanical and optical profiling, revealed thinner, denser and more homogeneous surface structure for polypyrrole films elaborated under ultrasound irradiation. This is attributed to cavitation bubble asymmetric collapse close to the interface, which should induce changes in the nucleation-growth mechanism during the first polymerization stage. An increase of approximately 27% in doping level for sonicated films was revealed by X-ray Photoelectron Spectroscopy (XPS) analyses.

High-sensitivity open-loop electronics for gravimetric acoustic-wave-based sensors

Detecting chemical species in gas phase has recently received an increasing interest mainly for security control, trying to implement new systems allowing for extended dynamics and reactivity. In this work, an open-loop interrogation strategy is proposed to use radio-frequency acoustic transducers as micro-balances for that purpose. The resulting system is dedicated to the monitoring of chemical compounds in gaseous or liquid-phase state. A 16 Hz standard deviation is demonstrated at 125 MHz, with a working frequency band in the 60 to 133 MHz range, answering the requirements for using Rayleigh- and Love-wave-based delay lines operating with 40-μm acoustic wavelength transducers. Moreover, this electronic setup was used to interrogate a high-overtone bulk acoustic wave resonator (HBAR) microbalance, a new sensor class allowing for multi-mode interrogation for gravimetric measurement improvement. The noise source still limiting the system performance is due to the analog-to-digital converter of the microcontroller, thus leaving open degrees-of-freedom for improving the obtained results by optimizing the voltage reference and board layout. The operation of the system is illustrated using a calibrated galvanic deposition at the surface of Love-wave delay lines to assess theoretical predictions of their gravimetric sensitivity and to compare them with HBAR-based sensor sensitivity.

Integrated Love Wave Device Dedicated to Biomolecular Interactions Measurements in Aqueous Media

Mass-sensitive electro-acoustic devices such as surface acoustic wave (SAW) micro-balances, capable to operate with aqueous media are particularly favorable for the development of biosensors. Their dimensions and physical properties offer a large potential in biological fluid investigations, especially for measuring physical phenomenon (mass deposition, adsorption, pressure…). In this work, we propose a specific grating configuration to lower the influence of viscosity of fluids which reduces the signal dynamics of the surface wave transducers. A dedicated liquid cell also has been developed to isolate the electro-active part of the device. The fabrication of the cell is achieved using theSU-8™ photo-resist, allowing for manufacturing thick structures preventing any contact between the tested liquids and the transducers. Furthermore, the sensing area has been optimized to optimize the sensor gravimetric sensitivity. The operation of the sensor is illustrated by detecting bovine serum albumin (BSA) adsorption in the sensing area.

SAW sensor exploiting palladium layer properties for selective detection of hydrogen

For an increasing number of application (energy production, car industry, space, etc.), hydrogen appears as a solution of the future as it is the most common body in the Universe (and therefore on Earth). However, due to its unstable properties, a particular care must be dedicated to control possible gaseous leaks close to facilities using this resource. Here we propose surface acoustic wave sensors for detecting gaseous hydrogen in standard environmental conditions (atmospheric pressure and room temperature). The proposed SAW sensors consists in two Rayleigh-wave delay lines built on Quartz. One equipped with a Palladium overlay and the other exhibiting a free path between the two interdigitated transducers. A dedicated hermetical gas test cell has been developed to test the efficiency of the sensor when exposed to hydrogen-composed atmospheres. A particular care was paid to avoid hydrogen leakage in the working environment and to perform the regeneration of the gas absorbing layer. The developed SAW devices exploiting hydrogen absorption capabilities of palladium layers exhibiting different thicknesses have been here used to make the detection and the identification of hydrogen concentrations (in the 0.25-2% range) diluted in nitrogen and is also able to make detection in current atmosphere. The effect of the palladium thickness variations along with the influence of an Yttrium doping of the palladium layer on the sensor behavior will be studied here.

Development of a high sensitivity anhydride hexafluorhydric acid sensor

This paper presents theoretical and experimental developments for the implementation of SAW sensors able to detect small concentration of anhydride HF acid in air. Solutions based on the used of surface transverse waves (STW) on quartz (YXlt)/36/spl deg//90/spl deg/ have been analysed to evaluate their potential sensitivity to HF. Devices have been first tested in a BHF solution to identify the kinetics of the reaction. Measurements have been then performed under various gaseous conditions to characterise their actual behaviour when submitted to controlled concentrations of HF. STW as well as love wave resonators have been successfully tested, with capabilities to detect HF concentration much smaller than 1 ppm.

Real Time Cascade Impactor Based On Surface Acoustic Wave Delay Lines for PM10 and PM2.5 Mass Concentration Measurement

In this research, Surface Acoustic Wave (SAW) sensors are combined with a cascade impactor to perform real time PM10 and PM2.5 mass concentration measurements. The SAW sensors consist of 125 MHz delay lines based on Love waves propagating on an AT-cut quartz substrate. The Love waves are guided on the substrate’s surface using a silica layer. SAW sensors themselves are not capable to discriminate particles by their size, therefore, particle separation based on aerodynamic diameter is achieved using a 3 Lpm dedicated cascade impactor. The latter was designed to integrate the SAW sensors which are monitored using a phase shift measurement. The collected particles impact on the acoustic sensor’s surface inducing a gravimetric effect that modifies the acoustic wave propagation conditions. The resulted phase shift allows the measurement of the mass deposited on the sensitive zone. The novel cascade impactor with SAW sensors as particle collecting stages is exposed to different aerosols in the 0–150 μg/m3 concentration range and proved to be able to detect and differentiate particles based on their size in real time. The system’s response was compared to a commercial optical counter based on light scattering technology and was found to be in good agreement with it.

Development of accurate system of gas detection based on Love wave sensors functionalized with cobalt corroles applied to the detection of carbon monoxide

We demonstrate here that surface acoustic wave devices give the means to exploit the molecular recognition events occurring in a non-conductive sensing layer. Using a specific test bench, we have monitored phase variations at constant frequency of Love waves generated by SAW devices, when loaded with carbon monoxide molecules. The devices used here are functionalized with cobalt corroles, which is a sensitive compound showing an attractive capability for carbon monoxide trapping. The test bench permits the regeneration of the trapping sites of carbon monoxide allowing the reusability of the devices. These good results pave the way to the detection of other gas and even particles.

Accurate measurement of anhydride fluorhydric acid concentration in controlled gaseous flow with STW sensors

This paper presents theoretical and experimental developments for the implementation of surface acoustic waves (SAW) sensors able to detect small concentrations of anhydride fluorhydric (HF) acid in air. Solutions based on the use of surface transverse waves (STW) on quartz (YXlt)/36° 90° have been analyzed to evaluate their sensitivity to HF. Devices have been tested first in a NH4F solution to evaluate the kinetics of the reaction. Measurements then were performed under various gaseous conditions to characterize the sensors when they are submitted to different controlled dilutions of HF in air. STW resonators have been successfully tested in different conditions, with capabilities to detect HF concentration much smaller than 1 ppm.