Papers by Mathieu Ducousso
Journal of The Acoustical Society of America, 2008
Picosecond ultrasonics is a non-destructive method for measuring mechanical properties such as ve... more Picosecond ultrasonics is a non-destructive method for measuring mechanical properties such as velocity or stiffness coefficients for nanometric materials. This technique uses femtosecond laser pulses for generating and detecting acoustics waves from GHz to THz. Its resolution is about nanometers in depth and a few micrometers laterally. For transparent materials it allows generating the so-called Brillouin oscillations, which frequencies are determined by the material sound velocity, the optical index and the light beam wavelength. In this paper this technique is applied to biological cells. Investigations deal on a single in-vitro living vegetal cell and are non destructive for the cell. 1D mapping, composed of 6 measurement points, in an Allium Cepa cell with a lateral resolutions of 1 µm and an in depth resolution of 0.1 µm is presented. Velocities and attenuations of sound are deduced from the Brillouin oscillation frequencies which are 5.7±0.3 and 6.8±0.3 GHz in the vacuole and the nucleus of the cell respectively.
Physics Procedia, 2010
A 100 fs laser pulse passes through a single transparent cell and is absorbed at the surface of a... more A 100 fs laser pulse passes through a single transparent cell and is absorbed at the surface of a metallic substrate. Picosecond acoustic waves are generated and propagate through the cell in contact with the metal. Interaction of the high frequency acoustic pulse with a probe laser light gives rise to stimulated Brillouin oscillations. The measurements are thus made with lasers for both the opto-acoustic generation and the acousto-optic detection. The technique offers perspectives for single cell imaging. The in plane resolution is limited by the pump and probe spot sizes, i.e 1 µm, and the in depth resolution is provided by the acoustic frequencies, typically in the GHz range. The effect of the technique on cell safety is discussed. Experiments achieved in vegetal cells illustrate reproducibility and sensitivity of the measurements. The acoustic responses of cell organelles are significantly different. The results support the potentialities of the hypersonic non invasive technique in the fields of bio-engineering and medicine.
The picosecond ultrasonic technique is applied for the non-invasive evaluation of sound velocity ... more The picosecond ultrasonic technique is applied for the non-invasive evaluation of sound velocity at a submicron scale in living onion cells. Velocity and attenuation of hypersound in cells are measured by a femtosecond laser pump-probe technique. A nanometric co-polymer layer deposited between the cell and the substrate has been used to improve the photoacoustic signal. Comparison of the measured signals with the photoacoustic responses calculated according to thermoelastic generation mechanism and reflectometric detection shows high sensitivity to the cell adhesion on substrate. Measurements achieved in different vegetal cells illustrate the sensitivity of the technique. In addition to single cell imaging with the high lateral resolution provided by optics (ie ≈1µm), the sensitivity of the measurements to cell compressibility suggests promising perspectives in the field of biology
The picosecond ultrasonic technique is applied for the non-invasive evaluation of sound velocity ... more The picosecond ultrasonic technique is applied for the non-invasive evaluation of sound velocity at a sub-micron scale in living onion cells. Velocity and attenuation of hypersound at 5.7 GHz in cells are measured by a femtosecond laser pump-probe technique. A nanometric co-polymer layer deposited between the cell and the substrate has been used to improve the photoacoustic signal. Comparison of the measured signals with the photoacoustic responses calculated according to thermoelastic generation mechanism and reflectometric detection shows high sensitivity to the cell adhesion on substrate. In addition to single cell imaging with the high lateral resolution provided by optics (ie !1µm), the sensitivity of the measurements to cell compressibility suggests promising perspectives in the field of biology.
ABSTRACT We use femtosecond laser pulses absorbed in a metallic transducer, namely the picosecond... more ABSTRACT We use femtosecond laser pulses absorbed in a metallic transducer, namely the picosecond ultrasonics technique, for the remote optical generation and detection of GHz acoustic frequencies in single cells by pump-probe sampling. Samples are MC3T3 cells adhering on a TiAl4V alloy substrate. Both pump and probe beams are focused at the cell/transducer interface. The pump absorption yields a temperature rise in the absorbing substrate and a picosecond acoustic pulse is generated through the thermoelastic effect. The probe beam is partially reflected from the metallic interface and partially scattered by the acoustic wavefront propagating in the transparent cell. The change of reflectivity of the cell is measured as a function of the pump-probe time delay. Interferences arise from the two probe contributions causing the so-called Brillouin oscillations. Optical phase variations due to acoustic-induced changes in cell thickness are simultaneously measured. The result of a semi-analytical calculation is fitted to the experimental data. Acoustic frequencies are detected at 30 GHz in the nucleus of single osteoblast cells.
The measurement of the mechanical properties of single biological cells with a nanometer depth re... more The measurement of the mechanical properties of single biological cells with a nanometer depth resolution using only coherent light is proposed. A pump-probe set-up based on an ultrafast laser (100 fs pulses) is used to excite and detect acoustic frequencies in the GHz range. Experiments are performed on single fixed mouse MC3T3 cells adhering on titanium alloy substrate. Using two
The measurement of the mechanical properties of single biological cells using a picosecond laser-... more The measurement of the mechanical properties of single biological cells using a picosecond laser-ultrasonic method is proposed. A pump-probe set-up based on ultrafast laser (100 fs pulses) is used to generate and detect acoustic frequencies in the GHz range in a cell on a metallic substrate. The time resolution is about 1 ps and the laser focusing allows a 1
ABSTRACT We present recent developments of our table-top femtosecond high flux harmonic beamline ... more ABSTRACT We present recent developments of our table-top femtosecond high flux harmonic beamline towards single-shot probing of magnetic nanostructures. High harmonic generation (HHG) optimization in a single and two-color infrared laser pulse mode was investigated at high laser energy. Up to 10^9 photons per harmonic are generated between 40 and 80 eV in a single femtosecond laser shot. These soft X-ray harmonic photons are employed to characterize at the nanoscale the magnetic network of Co/Pd multilayer samples using resonant small-angle X-ray scattering. Selecting harmonics in the vicinity of magnetically dichroic absorption resonances of cobalt and palladium (Co M2,3 at 60 eV and Pd N2,3 at 51 eV) gives access to the magnetic nanodomain spatial structure. The magnetic scattering efficiency at the Pd edge is found to be comparable to that at the Co edge. This indicates that the Pd layers exhibit a significant induced magnetic moment. Magnetic sample optimization is then performed by characterizing its scattering efficiency as a function of layer composition and number of repetitions. We finally measure the spatial organization of magnetic nanodomains with a sub-100 nm spatial resolution from a single femtosecond X-ray pulse.
ABSTRACT Understanding ultrafast dynamics of nanoscale objects is an important challenge in nanos... more ABSTRACT Understanding ultrafast dynamics of nanoscale objects is an important challenge in nanoscience and technology. Their investigation relies on the availability of ultrafast probe techniques capable of combining femtosecond time resolution with nanometer spatial resolution. Such experiments benefit greatly from the recent advent of x-ray free electron laser facilities. The extreme intensity of their short femtosecond x-ray pulses enables ultrafast snapshot characterization with nanoscale spatial resolution. Here, we demonstrate that such experiments are not uniquely limited to large-scale facilities, but that they can also be realized using high harmonics from a table-top femtosecond laser system. To do so, we have employed resonant magnetic x-ray scattering of a single 20 fs short XUV laser-harmonic pulse to characterize the nanometer sized magnetic domain structure of Co/Pd thin film. Moreover, the technique being element specific, we have looked at the domain structure within each of the two layer types by selecting harmonics resonant with the Co M-3 (60 eV) and the Pd N-3 (51 eV) edge, respectively.
We present single shot nanoscale imaging using a table-top femtosecond soft X-ray laser harmonic ... more We present single shot nanoscale imaging using a table-top femtosecond soft X-ray laser harmonic source at a wavelength of 32 nm. We show that the phase retrieval process in coherent diffractive imaging critically depends on beam quality. Coherence and image fidelity are measured from single-shot coherent diffraction patterns of isolated nano-patterned slits. Impact of flux, wave front and coherence of the soft X-ray beam on the phase retrieval process and the image quality are discussed. After beam improvements, a final image reconstruction is presented with a spatial resolution of 78 nm (half period) in a single 20 fs laser harmonic shot.
Ultrasonics, 2015
Available online xxxx 21 Keywords: 22 Picosecond ultrasonics 23 Cell mechanics 24 Cell adhesion 2... more Available online xxxx 21 Keywords: 22 Picosecond ultrasonics 23 Cell mechanics 24 Cell adhesion 25 2 6 a b s t r a c t 27 The mechanical properties of cells play a key role in several fundamental biological processes, such as 28 migration, proliferation, differentiation and tissue morphogenesis. The complexity of the inner cell com-29 position and the intricate meshwork formed by transmembrane cell-substrate interactions demands a 30 non-invasive technique to probe cell mechanics and cell adhesion at a subcell scale. In this paper we 31 review the use of laser-generated GHz acoustic waves-a technique called picosecond ultrasonics 32 (PU)-to probe the mechanical properties of single cells. We first describe applications to vegetal cells 33 and biomimetic systems. We show how these systems can be used as simple models to understand more 34 complex animal cells. We then present an opto-acoustic bio-transducer designed for in vivo measurement 35 in physiological conditions. We illustrate the use of this transducer through the simultaneous probing of 36 the density and compressibility of Allium cepa cells. Finally, we demonstrate that this technique can 37 quantify animal-cell adhesion on metallic surfaces by analyzing the acoustic pulses reflected off the 38 cell-metal interface. This innovative approach allows investigating quantitatively cell mechanics without 39 fluorescent labels or mechanical contact to the cell.
The Journal of the Acoustical Society of America, 2008
Picosecond ultrasonics is a non-destructive method for measuring mechanical properties such as ve... more Picosecond ultrasonics is a non-destructive method for measuring mechanical properties such as velocity or stiffness coefficients for nanometric materials. This technique uses femtosecond laser pulses for generating and detecting acoustics waves from GHz to THz. Its resolution is about nanometers in depth and a few micrometers laterally. For transparent materials it allows generating the so-called Brillouin oscillations, which frequencies are determined by the material sound velocity, the optical index and the light beam wavelength. In this paper this technique is applied to biological cells. Investigations deal on a single in-vitro living vegetal cell and are non destructive for the cell. 1D mapping, composed of 6 measurement points, in an Allium Cepa cell with a lateral resolutions of 1 µm and an in depth resolution of 0.1 µm is presented. Velocities and attenuations of sound are deduced from the Brillouin oscillation frequencies which are 5.7±0.3 and 6.8±0.3 GHz in the vacuole and the nucleus of the cell respectively.
The European Physical Journal Applied Physics, 2013
ABSTRACT The picosecond ultrasonics technique is used to investigate the viscoelastic properties ... more ABSTRACT The picosecond ultrasonics technique is used to investigate the viscoelastic properties of nucleus of fixed single osteoblast progenitor cells adhering on a titanium alloy substrate. A two-color probing picosecond ultrasonics and a fluorescence visualization setups were developed and combined to allow to distinguish subcomponents inside the cell under investigation. It opens the way for quantitative measurements of the viscoelastic properties of single cells and of their sub-micrometer thickness. It is shown that a blue probe, λ = 400 nm, is preferable to a red probe, λ = 800 nm, to perform these measurements with fixed sub-micrometer bone cells. 26 GHz acoustic frequencies are detected in cells as thin as 135 nm. A 1D analytical model of the acoustic generation and of the optical detection is used to describe the experimental results. The nucleus longitudinal elastic moduli (13-16 GPa) and dynamic viscosities (13-30 cP) are measured at high frequencies (GHz) from a time-frequency analysis of the experimental data of fixed single cells.
Physics Procedia, 2010
A 100 fs laser pulse passes through a single transparent cell and is absorbed at the surface of a... more A 100 fs laser pulse passes through a single transparent cell and is absorbed at the surface of a metallic substrate. Picosecond acoustic waves are generated and propagate through the cell in contact with the metal. Interaction of the high frequency acoustic pulse with a probe laser light gives rise to stimulated Brillouin oscillations. The measurements are thus made with lasers for both the opto-acoustic generation and the acousto-optic detection. The technique offers perspectives for single cell imaging. The in plane resolution is limited by the pump and probe spot sizes, i.e 1 µm, and the in depth resolution is provided by the acoustic frequencies, typically in the GHz range. The effect of the technique on cell safety is discussed. Experiments achieved in vegetal cells illustrate reproducibility and sensitivity of the measurements. The acoustic responses of cell organelles are significantly different. The results support the potentialities of the hypersonic non invasive technique in the fields of bio-engineering and medicine.
The picosecond ultrasonic technique is applied for the non-invasive evaluation of sound velocity ... more The picosecond ultrasonic technique is applied for the non-invasive evaluation of sound velocity at a submicron scale in living onion cells. Velocity and attenuation of hypersound in cells are measured by a femtosecond laser pump-probe technique. A nanometric co-polymer layer deposited between the cell and the substrate has been used to improve the photoacoustic signal. Comparison of the measured signals with the photoacoustic responses calculated according to thermoelastic generation mechanism and reflectometric detection shows high sensitivity to the cell adhesion on substrate. Measurements achieved in different vegetal cells illustrate the sensitivity of the technique. In addition to single cell imaging with the high lateral resolution provided by optics (ie ≈1µm), the sensitivity of the measurements to cell compressibility suggests promising perspectives in the field of biology
Femtosecond magnetization phenomena have been challenging our understanding for over a decade. mo... more Femtosecond magnetization phenomena have been challenging our understanding for over a decade. most experiments have relied on infrared femtosecond lasers, limiting the spatial resolution to a few micrometres. With the advent of femtosecond X-ray sources, nanometric resolution can now be reached, which matches key length scales in femtomagnetism such as the travelling length of excited 'hot' electrons on a femtosecond timescale. Here we study laser-induced ultrafast demagnetization in [Co/Pd] 30 multilayer films, which, for the first time, achieves a spatial resolution better than 100 nm by using femtosecond soft X-ray pulses. This allows us to follow the femtosecond demagnetization process in a magnetic system consisting of alternating nanometric domains of opposite magnetization. no modification of the magnetic structure is observed, but, in comparison with uniformly magnetized systems of similar composition, we find a significantly faster demagnetization time. We argue that this may be caused by direct transfer of spin angular momentum between neighbouring domains.
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Papers by Mathieu Ducousso