Smart-UltraSound: Detection/characterization/control of non-linear ultrasonic sources – Smart US

Non-Linear (NL) Harmonic Imaging procedures (such as Pulse Inversion, Amplitude and Phase Modulations…) implemented in modern echographs have lead to improved sensitivity and specificity. In order to enlarge the detection range (nanobubbles) and to permit biphasic characterization (bubble histogram, void fraction, flow rate…) the “Smart US” project aims at developing two new technologies: a Magneto-Acoustic Sensor (MAS) and a Smart Parametric Sensor (SPS). The latter relies on the NL interaction of the ultrasonic wave and the bubbly medium. These NL transducers possess exceptional acoustical properties such as: Phase Conjugation induced automatic focusing, NL detection, very broadband activation, and dynamical controls of directivity and of spectral content. For the purpose of bubble generation, microfluidic techniques coupled with nano-electrolysis will be implemented. Biphasic microfluidics permits the production of bubbles with polydispersity less than 2%. Generating submicron bubbles requires that a change of scale (nanofluidics) be performed and that the associated difficulties be dealt with (manufacturing technology, flux and nanostructure instabilities …). Besides, microfluidics enables the manufacturing of auto-structured microbubble crystals whose NL behavior will be studied. Alternatively, nanoelectrolysis permits the spatial and temporal controls of the nucleation event thanks to the use of electrodes of nano-size (~10 nm) that generate high electrical gradients. The shape, size, surface processing and fluid nature considerably modify the generation and detachment of the nanobubbles.

Calibrated microbubbles whose size ranges from 20 to 150 microns have been produced with a good reproducibility by using microfluidics or microelectrolysis means.
Besides, numerical models have been designed that depict from the one hand, the dynamical behavior of a single bubble, and on the other hand, the ultrasonic wave propagation in biphasic media. Such models will help in optimizing sizing bubble technics as well as parametric acoustic radiation respectively.
First bubble crystals have been manufactured, however the reticulated material that constitutes the matrix still needs to be softened for an efficient acoustic radiation.
Furthermore, this nano-electrolysis permits the nucleation of a unique bubble which proves useful for physical studies on wave/single bubble interaction.

In order to enlarge the detection range (nanobubbles) and to make possible biphasic characterization (bubble histogram, void fraction, flow rate…), “Smart US” project aims at developing:
1/ bubble-generation tools: Biphasic microfluidics enables both the production of bubbles with a good reproducibility and the manufacturing of auto-structured microbubble crystals. Now, one objective is to reach submicron sizes. Alternatively, nanoelectrolysis (electrodes ~10 nm) enables the spatial and temporal controls of the nucleation of a single bubble.
2/ detection and characterization sensors: magneto-acoustic interaction induces a wave conjugation similar to the LASER (pumping) effect which produces a giant amplification (~80dB) and permits automatic focusing on echoic objects (i.e. a bubble) or assessment of speed profiles and gas concentration. Besides, the bubbly medium behavior is expected to offer new perspectives in adaptive parametric transduction. For instance, these NL transducers will transmit waves very similar (“wave matching”) to those scattered by bubbles: hence the name “Smart US. The strong coupling that will result will improve the biphasic characterization performances.
3/ design of wave/bubble interaction model and of Signal Processing technics that extract weak NL information in noisy environment.

Revues
MC. Pauzin, S. Mensah, B. Cochelin, JP. Lefebvre, « High order harmonic balance formulation of free and encapsulated microbubbles », J. of Sound and Vibration, 330 (2011) 987 – 1004.

Fabien Chauvet, Sandrine Geoffroy, Abdelkrim Hamoumi, Marc Prat and Pierre Joseph, “ Roles of gas in capillary filling of nanoslits”, Accepted for publication in Soft Matter (2012)
DOI: 10.1039/c2sm25982f

Congrès internationaux
T. Goursole, B. Potier, D. Fouan, S. Mensah, « Free Single Excitation applied to nonlinear mixing method », Undersea & Hyperbaric Medical Society, Fort Worth, Texas, June 15-18, 2011

Fabien Chauvet, Sandrine Geoffroy, Abdelkrim Hamoumi, Marc Prat, Anne-Marie Gué and Pierre Joseph, « Nanobubbles and Gas Dynamics During Capillary Filling of Nanoslits », Proceedings of µTAS 2010 Conference, Okinawa, Japan, 26-30 Oct 2012

Z. Hammadi, R. Grossier, R. Morin, S. Veesler “Predictive Nucleation of Crystals” 10th International Conference of the Crystal Growth of Organic CGCOM 10 11-14 Juin 2012 Limerick, Irlande

M. Cavaro , C. Payan, S. Mensah , J. Moysan, JP. Jeannot, « Linear and nonlinear resonant acoustic spectroscopy of microbubble clouds », XVII International Conference on Nonlinear Elasticity in Materials, Cefalu, Sicily, Italy, 1 - 7 July 2012

The generation, the detection and the characterization of [0.1-150]-micron bubbles may be crucial in various situations. In the medical field, one can mention the development and characterization of Ultrasound Contrast Agents, the prevention of cardiac or pulmonary embolisms and of decompression sickness. Present in blood or in tissues (under the form of gas nuclei), these bubbles may result from super-saturation (decompression) or may originate from prosthetic heart valves or in dialysis and cardiopulmonary bypass machines. In the industrial context, specific concerns deals with the presence of microbubbles in the liquid sodium which biases the UltraSonic (US) control channels with possibly heavy consequences for the core security.

Non-Linear (NL) Harmonic Imaging procedures (such as Pulse Inversion, Amplitude and Phase Modulations…) implemented in modern echographs have lead to improved sensitivity and specificity.
In order to enlarge the detection range (nanobubbles) and to permit biphasic characterization (bubble histogram, void fraction, flow rate…) the “Smart US” project aims at developing two new technologies : a Magneto-Acoustic Sensor (MAS) and a Smart Parametric Sensor (SPS). The latter is built on the basis of a crystal of calibrated microbubbles embedded in a polymeric microstructure. These NL transducers possess exceptional acoustical properties such as : Phase Conjugaison induced automatic focussing, automatic NL detection, very broad band activation, dynamical controls of directivity and of spectral content.

For the purpose of bubble generation, microfluidic techniques coupled with nano-electrolysis will be implemented. Biphasic microfluidics permits the production of bubbles with polydispersity less than 2%. Generating submicron bubbles requires that a change of scale (nanofluidics) be performed and that the associated difficulties be dealt with (manufacturing technology, flux and nanostructure instabilities …). Besides, microfluidics enables the manufacturing of auto-structured microbubble crystals. Hence, the original idea which consists of integrating these crystals within the active lens of the US transducers in order to obtain SPS.

Alternatively, nanoelectrolysis permits the spatial and temporal controls of the nucleation event thanks to the use of electrodes of nano-size (~10 nm) that generate high electrical gradients. The shape, size, surface processing and fluid nature considerably modify the generation and detachment of the nanobubbles. Furthermore, this nano-electrolysis permits the nucleation of a unique bubble in gels (i.e. which can mimic tissues) which proves useful for physical studies on wave/single bubble interaction.

MAS is based on magnetic interaction with piezoelectrical material which induces a wave conjugation similar to the LASER (pumping) effect. This interaction produces a giant amplification (~80dB) of the conjugated wave. This analogical time reversal equivalent process can compensate for phase distortions induced by wave propagation in heterogeneous media; this means can produce an automatic focusing on echoic objects (i.e. a bubble). Besides, field reversibility breakage induced by medium movement (flows) offers a good means to assess speed profiles and gas concentration.

Finally, these NL transducers will transmit waves very similar (“wave matching”) to those scattered by bubbles: hence the name “Smart US”. The strong coupling that will result will improve the biphasic characterization performances.