February 2014 Romain Legrand joins the team as a postdoctoral researcher.
January 2014 Starting of the ANR grant "Picosecond ultrasonics for quantitative imaging of single cells adhesion on biomaterials".
October 2013 Thomas Dehoux received a CNRS Bronze medal

February 2013 Listening to Cells: Scientists Probe Human Cells With High-Frequency Sound

The production of audible sound with the focusing and modulation of sun light has been demonstrated since the 19th century. The modern application of this idea relies on the development of controllable coherent light sources such as lasers. Higher frequency acoustic waves propagating in solids or liquids, namely ultrasounds, could then be generated and detected at a distance without any contact to the specimen.

Laser opto-acoustics is thus a field where acoustic waves, potentially of extremely high frequencies (up to THz), are both generated and detected with short lasers pulses (fs). The team has been developing researches on the opto-acoustic transduction and on the acousto-optic detection relevant with acoustic propagation in viscoelastic materials or materials with anisotropy. The opto-acoustics of thin layers or fibres has been under the scope of their interest. Recent researches are focused on the dynamic response of single nanoparticles, and on the laser opto-acoustic elastography of single biological cells.

The group has notably demonstrated that the picosecond opto-acoustic technique in a reflectometry configuration is suitable to optically generate and detect hypersonic waves in the volume of a single sub-micronic gold particle and in the surrounding matrix. The very high frequencies involved in the acoustic spectra of nano-particles are extremely promising for imaging micrometric to nanometric structures.

In parallel, the team has demonstrated the suitability of the picosecond opto-acoustic technique for hypersound generation and detection in single biological cells. Exciting abilities for the non-invasive study of a cell and of organelles have been reported. These abilities developed in nano-phononics, based on the diffraction of optically generated acoustic pulses with nm wavelength, contribute to the development of innovative multi-physics imaging processes.

Picosecond biophononics


Understanding the mechanical properties of cells and their relation to different physiological conditions is essential to the study of fundamental processes such as proliferation, migration, or differentiation. Early techniques (micropipette aspiration AFM...) proposed quasistatic measurements averaged over the whole cell structure. Yet cells have a complex composition that yields an intricate dynamical behavior, appealing for measurements over a wide frequency range at a sub-cell scale. To this end, much effort is being made to develop new investigation means. However, the existing techniques cannot exceed the kHz range, and only a small part of the relaxation spectrum of cells is known. Moreover, these techniques rely for most on contacting or injected functionalized microprobes, which renders the probing of the cell mechanical properties difficult during biological processes.

We have recently demonstrated that the coherent generation of GHz acoustic waves using ultrashort laser pulses, namely picosecond ultrasonics, can efficiently probe the sound velocity in vegetal cells and in cell-mimicking soft micro-objects with micrometer resolution, suggesting tremendous potentialities for single-cell biology. Traditionally devoted to the investigation of solids, this pump-probe technique has only recently been applied to simple fluids, and its application to soft matter remains elusive and extremely challenging. The aim of this work is to investigate the nanomechanical properties of cells and of soft matter using laser-generated GHz ultrasound, in relation with biological processes.

Probing the contact between cells and a biomaterial

The measurement of picosecond ultrasonic pulses reflected from contacting interfaces has recently been demonstrated to be a promising new line of investigation for the characterization of nanoscale mechanical contacts between solids. [1] Using coherent phonon-pulse reflection from—and heat flow across—a mechanical contact of nanoscale thickness between a thin metal film and a spherical dielectric indenter, the film deformation in situ was revealed.

However, manipulating biological media in physiological conditions is often a technical challenge when using a laser-based setup. We have therefore designed a new opto-acoustic bio-transducer composed of a thin metal film sputtered on a transparent heat sink that allows reducing importantly the laser-induced cellular stresses, and offers a wide variety of optical configurations (see figure 1). In particular, by exploiting the acoustic reflection coefficient at the sample-transducer interface and the photoacoustic interaction inside the transparent sample, we have probed simultaneously the density and compressibility of a single vegetal cell. [2].

Figure 1: The new opto-acoustic bio-transducer allows reducing importantly the laser-induced cellular stresses and offers a wide variety of optical configurations.

We have also demonstrated the ability of this technique to image non-specific contacts of single animal cells with metallic substrates. We have developed new signal analysis tools to perform such studies at various frequencies. We cultured monocytes on top of the opto-acoustic bio-transducer. Low-energy femtosecond pump laser pulses are focused at the bottom of the Ti film to a micron spot. The subsequent ultrafast thermal expansion launches a longitudinal acoustic pulse in Ti, with a broad spectrum extending up to 200 GHz. We measured the acoustic echoes reflected from the film/cell interface through the transient optical reflectance changes. The time-frequency analysis of the reflected acoustic pulses with a wavelet transform gives access to a map of the acoustic impedance of the cell and of the stiffness of the film-cell interface (figure 2). [3]

Figure 2: (a) Set-up. (b) Scanning electron microscope image of monocytes. (c) White-light image of the probed area. The scanned line is indicated with a red dotted line. (d) Acoustic reflection coefficient across the cell contact area at frequencies 30 GHz (black) and 60 GHz (grey). (e) Measured (black plain line) and theoretical (red dashed line) reflection coefficient vs frequency at three positions in the first cell (8, 14 and 20 µm). These positions are indicated in Fig. 2(d) with red dots.

Related publications :
[1] T. Dehoux et al., Phys. Rev. B 80, 235409 (2009)
[2] T. Dehoux et al., J. Appl. Phys. 112, 124702 (2012)
[3] M. Abi Ghanem et al., J. Biophoton. (2013)

Relaxation dynamics in single polymer microcapsules

Soft polymer micro-objects are of great interest for their biological cell-mimicking properties their encapsulation capacities, their use as contrast agents for ultrasonic imaging, as well as their use in self-healing materials. All the same, their compressibility, viscosity and shell thickness play an important role in the adhesion involved in specific tissues targeting, in the drug release rate, or in their echogenicity. However, at submicrometer scales, controlling these properties is challenging and requires elaborate characterization methods.

In particular, a large body of work has been devoted to microcapsules due to their potential in the food and pharmaceutical industries. Microcapsules are mostly used at MHz frequencies, and their individual rheological behavior is usually inferred from their collective response by modelling. Correlating the input of these models with the mechanics of single capsules at higher frequencies is therefore of the utmost importance to complete the description of their intricate dynamics in view of improving their design and modelling.

Using an ultrafast optical technique (Fig. x, left) we probe coherent-phonon propagation inside a single microcapsule composed of a nanometric polymer shell made of poly(lactide-co-glycolide) (PLGA) encapsulating a liquid perfluorooctyl bromide (PFOB) core. Longitudinal storage and loss moduli are measured simultaneously in the transparent shell and core at frequencies ~18 and ~4 GHz, respectively, using time-resolved Brillouin spectroscopy (Fig. x, right). A time-frequency analysis allows determination of the thickness of several capsule shells ranging from 620 down to 80 nm. Comparison with lower frequency data shows a weak power-law frequency dependence of phonon attenuation in the PLGA shell, signature of thermally activated processes in glasses.

Related publications :
T. Dehoux, N. Tsapis and B. Audoin, "Relaxation dynamics in single polymer microcapsules probed with laser-generated GHz acoustic waves", Soft Matter 8, 2586 (2012)

Back to top



A promising way to locally probe the elasticity of micrometric to nanometric structures (e.g. solid state devices, biological media) is to exploit the high frequency acoustic field radiated by a single nanoparticle (NP). For instance, the femtosecond optical excitation of a 100 nm diameter gold nanoparticle generate in water an acoustic field with a 50 nm acoustic wavelength, i.e. far below the best optical resolution. The aim of this project is to design local GHz opto-acoustic transducers.

Nanoparticle mediated generation of GHz longitudinal acoustic waves

The optoacoustic response of a single submicron (430 nm) gold particle embedded in a silica thin film has been experimentally revealed by transient reflectivity measurements with a femtosecond pump-probe setup. The detection mechanism relies on an intrinsic common-path interferometer where the reference beam comes from a fixed interface of the sample. A semianalytical model is developed to calculate the transient reflectivity accounting for optical index changes in both media and for particle and film surface displacements. The displacement of the particle-film interface turns out to be the major contribution to the measured signal.

Related publications :
Y. Guillet et al. Appl. Phys. Lett. 95, 061909 (2009)
Y. Guillet et al. J. Phys.: Conf. Ser. 214, 012046 (2010)

All-optical probing of a single nanoparticle-substrate contact

We investigate the GHz dynamics of the elastic contact between a single metallic nanoparticle and a substrate. We detect the known breathing mode of the nanoparticle but we also unravel the axial oscillation of the nanoparticle through an intrinsic common-path interferometer. We measured the eigenfrequency and the lifetime of this vertical motion, which are related to the contact stiffness and hysteresis, and to the acoustic leakage at the nanoparticle-substrate interface. Measurements have been performed for single particles with radii ranging from 60 to 700 nm.

Related publication :
Y. Guillet et al. Phys. Rev. B. 86, 035456 (2012)

Back to top

Group members

Abi Ghanem
PhD Studentmaroun.abighanem_AT_etu.u-bordeaux1.fr33 (0)5 40 00 87 87
Group coordinator
bertrand.audoin_AT_u-bordeaux1.fr33 (0)5 40 00 69 69
PhD Studentjulien.chandezon_AT_etu.u-bordeaux1.fr33 (0)5 40 00 89 30
thomas.dehoux_AT_u-bordeaux1.fr33 (0)5 40 00 62 21
yannick.guillet_AT_u-bordeaux1.fr33 (0)5 40 00 66 12
Postdocromain.legrand_AT_u-bordeaux.fr33 (0)5 40 00 89 30
clement.rossignol_AT_u-bordeaux1.fr33 (0)5 40 00 62 21
PhD Studentalexis.viel_AT_etu.u-bordeaux1.fr33 (0)5 40 00 87 87
Postdocfeng.xu_AT_u-bordeaux1.fr33 (0)5 40 00 89 30

Former group members

Allaoua AbbasPhD 2010 - 2013
Nikolay ChigarevPostdoc 2004 - 2007
Mathieu DucoussoPhD Student 2007 - 2010
Atef GadallaPostdoc 2011 - 2012
Julien HiguetPostdoc 2010 - 2011
Claude InserraPostdoc 2008 - 2009
Hinde MeriPhD Student 2001 - 2004
Salvatore MinissalePostdoc 2012 - 2013
Yongdong PanAssociate assistant professor 2001-2008
Mathieu PertonPhD Student 2003 - 2006
Damien SégurPhD Student 2006 - 2009
Samuel RaetzPhD Student 2009 - 2012
Tony Valier-BrasierPostdoc 2010 - 2011

Back to top


2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 | 1999 | 1998 | 1997 | 1996


  • Picosecond time resolved opto-acoustic imaging with 48 MHz frequency resolution
    A. Abbas, Y. Guillet, J.-M. Rampnoux, P. Rigail, E. Mottay, B. Audoin and S. Dilhaire
    Opt. Express 22, 7821 (2014)

  • Transverse mechanical properties of cell walls of single living plant cells probed by laser-generated acoustic waves
    A. Gadalla, T. Dehoux and B. Audoin
    Planta (2014)

Back to top


  • Acoustic beam steering by light refraction: Illustration with directivity patterns of a tilted volume photoacoustic source
    S. Raetz, T. Dehoux, M. Perton and B. Audoin
    J. Acoust. Soc. Am. 134, 4381 (2013)

  • Remote opto-acoustic probing of single-cell adhesion on metallic surfaces
    M. Abi Ghanem, T. Dehoux, O. F. Zouani, A. Gadalla, M.-C. Durrieu and B. Audoin
    J. Biophoton. (2013)

Back to top


  • Non-invasive optoacoustic probing of the density and stiffness of single biological cells
    T. Dehoux and B. Audoin
    J. Appl. Phys 112, 124702 (2012)

  • All-optical ultrafast spectroscopy of a single nanoparticle-substrate contact
    Y. Guillet, B. Audoin, M. Ferrié and S. Ravaine
    Phys. Rev. B 86, 035456 (2012)

  • Scaled behavior of interface waves at an imperfect solid-solid interface
    T. Valier-Brasier, T. Dehoux and B. Audoin
    J. Appl. Phys. 112, 024904 (2012)

  • Relaxation dynamics in single polymer microcapsules probed with laser-generated GHz acoustic waves
    T. Dehoux, N. Tsapis and B. Audoin
    Soft Matter 8, 2586 (2012)

Back to top


Back to top


  • Picosecond time scale imaging of mechanical contacts
    T. Dehoux, O. B. Wright and R. Li Voti
    Physics Procedia 3, 351 (2010)

  • Bulk waves excited by a laser line pulse in a two-layered cylinder
    Y. D. Pan, N. Chigarev and B. Audoin
    J. Appl. Phys. 107, 023527 (2010)

  • Intrinsic geometric scattering probed by picosecond optoacoustics in a cylindrical cavity: Application to acoustic and optical characterizations of a single micron carbon fiber
    D. Ségur, Y. Guillet and B. Audoin
    Appl. Phys. Lett. 97, 031901 (2010)

  • Experimental and theoretical study of acoustic waves generated by a laser line pulse in an optically absorptive isotropic cylinder
    D. Ségur, A. L. Shuvalov, B. Audoin and Y. D. Pan
    J. Acoust. Soc. Am. 127, 181-185 (2010)

  • Picosecond acoustics in vegetal cells: Non-invasive in vitro measurements at a sub-cell scale
    B. Audoin, C. Rossignol, N. Chigarev, M. Ducousso, G. Forget, F. Guillemot and M.C. Durrieu
    Ultrasonics 50, 202-207 (2010)

  • One-Pot Radiolytic Synthesis of Gold Nanorods and Their Optical Properties
    W. Abidi, P. R. Selvakannan, Y. Guillet, I. Lampre, P. Beaunier, B. Pansu, B. Palpant and H. Remita
    J. Phys. Chem. C 114, 14794-14803 (2010)

  • Bulk waves excited by a laser line pulse in a bi-layer cylinder
    Y. D. Pan, N. Chigarev and B. Audoin
    J. Phys. Conf. Ser. 214, 012044 (2010)

  • Photo-acoustic response of a single 430 nm gold particle: Semi-analytical model and picosecond ultrasonics measurements
    Y. Guillet, C. Rossignol, B. Audoin, G. Calbris and S. Ravaine
    J. Phys.: Conf. Ser. 214, 012046 (2010)

  • Picosecond acoustics in vegetal cells: non invasive in vitro measurements at a sub-cell scale
    B. Audoin, C. Rossignol, N. Chigarev, M. Ducousso, G. Forget, F. Guillemot and M.-C. Durrieu
    Physics Procedia 3, 323-321 (2010)

Back to top


Back to top


Back to top


  • Three-dimensional elasto-optical interaction for reflectometric detection of diffracted acoustic fields in picosecond ultrasonics
    T. Dehoux, N. Chigarev, C. Rossignol and B. Audoin
    Phys. Rev. B 76, 024311 (2007)

  • Coherent phonons in Si/SiGe superlattices
    Y. Ezzahri, S. Grauby, J. M. Rampnoux, H. Michel, G. Pernot, W. Claeys, S. Dilhaire, C. Rossignol, G. Zeng and A. Shakouri
    Phys. Rev. B 75, 195309 (2007)

  • Theory and illustration of the three-dimensional elasto-optic interaction in picosecond ultrasonics
    T. Dehoux, N. Chigarev, C. Rossignol and B. Audoin
    J. Phys. Conf. Ser. 92, 012020 (2007)

  • Picosecond acoustic diffraction in anisotropic thin film (µm); application to the measurement of stiffness coefficients
    B. Audoin, M. Perton, N. Chigarev and C. Rossignol
    J. Phys. Conf. Ser. 92, 012028 (2007)

  • Surface waves in highly ordered poly-graphite and gold micro-layers studied by picosecond ultrasonic technique
    N. Chigarecv, T. Dehoux, C. Rossignol, B. Audoin, and V. Levin
    J. Phys. Conf. Ser. 92, 012029 (2007)

  • Thermal diffusivity of a metallic thin layer using the time-domain thermo reflectance technique
    J. L. Battaglia, A. Kusiak, C. Rossignol and N. Chigarev
    J. Phys. Conf. Ser. 92, 012083 (2007)

  • Calculation of the dispersion curves of a functionally graded hollow cylinder
    Y. Zhao, Y. D. Pan, C. Rossignol and B. Audoin
    J. Phys. Conf. Ser. 92, 012106 (2007)

  • Beam distortion detection technique for picosecond ultrasonics
    N. Chigarev, C. Rossignol and B. Audoin
    J. Phys. Conf. Ser. 92, 012178 (2007)

  • Picosecond acoustic measurement of anisotropic properties of thin films
    M. Perton, C. Rossignol, N. Chigarev and B. Audoin
    AIP Conf. Proc. 894, 1148-1158 (2007)

Back to top


  • Two-dimensional diffraction of plasma, thermal, and elastic waves generated by an infrared laser pulse in semiconductors
    B. Audoin, H. Meri and C. Rossignol
    Phys. Rev. B. 74, 214304 (2006)

  • Surface displacement measured by beam distortion detection technique: Application to picosecond ultrasonics
    N. Chigarev, C. Rossignol and B. Audoin
    Rev. Sci. Instrum. 77, 114901 (2006)

  • Effect of laser pulse duration in picosecond ultrasonics
    T. Dehoux, M. Perton, N. Chigarev, C. Rossignol, J.-M. Rampnoux, and B. Audoin
    J. Appl. Phys. 100, 064318 (2006)

  • Bulk conical and surface helical acoustic waves in transversely isotropic cylinders; application to the stiffness tensor measurement
    M. Perton, B. Audoin, Y. D. Pan and C. Rossignol
    J. Acoust. Soc. Am. 119, 3752-3759 (2006)

  • Picosecond ultrasonics time resolved spectroscopy using a photonic crystal fiber
    C. Rossignol, J. M. Rampnoux, T. Dehoux, S. Dilhaire, and B. Audoin
    Rev. Sci. Instrum. 77, 033101 (2006)

  • Acoustic waves generated by a laser point pulse in a transversely isotropic cylinder
    Y. D. Pan, M. Perton, B. Audoin, and C. Rossignol
    J. Acoust. Soc. Am. 119, 243-250 (2006)

  • The transient response of a transversely isotropic cylinder under a laser point source impact
    Y. D. Pan, M. Perton, C. Rossignol, and B. Audoin
    Ultrasonics 44, E823-E827 (2006)

  • Acoustic waves generated by a laser line pulse in a hollow cylinder
    Y. D. Pan, L. Li, C. Rossignol, B. Audoin and N. Chigarev
    Ultrasonics 44, E843-E847 (2006)

  • Numerical analysis of bulk conical waves in anisotropic cylinders; application to stiffness tensor measurement
    M. Perton, B. Audoin, Y. D. Pan and C. Rossignol
    Ultrasonics 44, E859-E862 (2006)

  • On the use of laser-ultrasonics technique to excite selectively cylinder acoustic resonances
    B. Audoin, Y. D. Pan, C. Rossignol and N. Chigarev
    Ultrasonics 44, E1195-E1198 (2006)

  • Identification of laser-generated ultrasounds in the response of the cylinder over time and space
    Y. D. Pan, C. Rossignol, B. Audoin an dN. Chigarev
    Ultrasonics 44, E1249-E1253 (2006)

  • Picosecond ultrasonics time resolved spectroscopy using a photonic crystal fiber
    C. Rossignol, J. M. Rampnoux, T. Dehoux, S. Dilhaire, and B. Audoin
    Ultrasonics 44, E1283-E1287 (2006)

Back to top


Back to top


Back to top


  • Acoustic waves generated by a laser line pulse in a transversely isotropic cylinder
    Y. D. Pan, C. Rossignol and B. Audoin
    Appl. Phys. Lett. 82, 4379-4381 (2003)

  • Laser generation of acoustic waves in an anisotropic medium; parametric analysis for application to material characterization
    C. Rossignol, H. Meri and B. Audoin
    Rev. Sci. Instrum. 74, 470 (2003)

  • Application of picosecond ultrasonics to non-destructive analysis in VLSI circuits
    G. Andriamonje, V. Pouget, Y. Ousten, D. Lewis, Y. Danto, J. M. Rampnoux, Y. Ezzahri, S. Dilhaire, S. Grauby, W. Claeys, C. Rossignol and B. Audoin
    Microelectron. Reliab. 43, 1803-1807 (2003)

  • Generation and detection of ultrasonic waves in micrometric and sub-micrometric films using picosecond laser pulses
    C. Rossignol, R. Libgot, B. Audoin, J.-M. Rampnoux and S. Dilhaire
    2003 IEEE Ultrasonics Symposium, 286-293 (2003)

Back to top


Back to top


  • Ultrasonic measurement of elastic constants of anisotropic materials with laser source and laser receiver focused on the same interface
    F. Reverdy and B. Audoin
    J. Appl. Phys. 90, 4829-4835 (2001)

  • Elastic constants determination of anisotropic materials from phase velocities of acoustic waves generated and detected by lasers
    F. Reverdy and B. Audoin
    J. Acoust. Soc. Am. 109, 1965-1972 (2001)

  • Extension to cuspidal edges of wave surfaces of anisotropic solids: Treatment of near cusp behavior
    O. Poncelet, M. Deschamps, A. G. Every and B. Audoin
    AIP Conf. Proc. 557, 51-58 (2001)

  • Characterization of temperature-induced stiffness changes in a C-PMR15 composite material by means of laser generated and detected ultrasound
    S. Guilbaud and B. Audoin
    Compos. Sci. Technol. 61, 433-438 (2001)

Back to top


Back to top


Back to top


Back to top


  • Measurement by LASER-Generated Ultrasound of Four Stiffness Coefficients of an Anisotropic Material at Elevated Temperatures
    B. Audoin and C. Bescond
    J. Nondestr. Eval. 16, 91-100 (1997)

Back to top


  • Measurement of stiffness coefficients of anisotropic materials from pointlike generation and detection of acoustic waves
    B. Audoin, C. Bescond and M. Deschamps
    J. Appl. Phys. 80, 3760-3771 (1996)

  • Bulk and surface waves in anisotropic solids generated with pulsed laser beam: Comparison between theory and experiment
    C. Bescond, M. Deschamps and B. Audoin
    Prog. Nat. Sci. 6, S374-S377 (1996)

  • Ultrasonic displacement field generated by a laser pulse line source in a homogeneous semi-infinitive medium
    M. Qian, Y. Pan, C. Bescond, M. Deschamps, and B. Audoin
    Prog. Nat. Sci. 6, S378-S381 (1996)

Back to top