Alberto Varela Feijoo

Philippe Djemia

Tetsuharu Narita

Frédéric Pignon

Alain Ponton

Multiscale

Multiscale investigation of viscoelastic properties of biopolymer matrices

Macrorheology

Brillouin spectroscopy  Low cytotoxicity for alginate concentration of 10 g/L at 48 h.

 Good agreement between the results of macro and micro rheology.

 Continuous study of the viscoelastic properties between 10 -2 -10 5 Hz.

Determination of viscoelastic properties

 Determination of the mean square displacement of microparticles undergoing a Brownian motion in viscoelastic media.

 Brillouin scattering: exchange of energy with thermally driven acoustic waves, leading to a frequency shift between incident and scattered light.

Frequency••

  Photon counterCorrelator

•

  Entangled Polystyrene spherical microparticles Alkyl-OH surface (ϕ = 500 nm, conc. = 1%) l*: sample transport mean free path L: sample thickness k I k S I n c i d e n t l i g h t S c a t t e r e d l i g h t Scattered light Incident light Scattered light: Stokes (W 0 -W,K 0 -K) Anti-Stokes (W 0 +W,K 0 +K) Results obtained by macro-rheology and Diffusing-Wave Spectroscopy (DWS) in a reasonably good agreement to investigate viscoelastic properties of aqueous solutions of sodium alginate over 7 frequency decades (10 -2 -10 5 Hz) with a transition from viscous to elastic behavior as the frequency is increased.  The complementary results of Brillouin spectroscopy confirms a viscoelastic behaviour at 10 9 Hz range dominated by an elastic behavior.  Estimation of a fractal dimension from SAXS measurements  Aqueous solutions of sodium alginate present a good biocompatibility as confirmed by cell viability Obtention of Brillouin spectra of scattered light (Stokes and anti-Stokes peaks)  Fitting of the peaks with a Voigt function to f L (and C 11 ) and Γ (and η)  Substraction of device linewidth: Gaussian σ = 0Bending mode (high 𝜔𝜔) (𝜔𝜔 = 2 π f) 𝐺𝐺 * ~𝜔𝜔5/9 Zimm-Rouse mode (lower 𝜔𝜔) 𝑥𝑥 𝑤𝑤 . 𝑀𝑀 𝑤𝑤 + (1 -𝑥𝑥 𝑤𝑤 )𝑀𝑀 𝑎𝑎𝑎𝑎𝑎𝑎 • x w : mass fraction of water • C 11 : elastic constant determined for alginate solution at different concentrations • M w : elastic constant determined for water • M alg : "intrinsic" elastic constant of alginate Polymer network European Synchrotron Radiation Facility (ESRF, Grenoble, France) λ RX = 0.1 nm, sample-to-detector distances between 2 m and 31 m.2.10 -3 nm -1 ≤ q ≤ 3.5 nm -1 , 1.8 nm ≤ λ ≤ 3141 nm