ESPCI web site
ESPCI Paris
Lieu de travail
Paris - Ile-de-France - France
Intitulé du sujet
Gel fracture : processes involved at the vicinity of an advancing crack using shear wave elastography
Champs scientifiques
Chimie
Physique
Description
Gels are fascinating materials in the field of materials science and engineering. Gels behave like soft elastic solids despite being water-based, containing typically 90 wt% of water. Based on gel’s remarkable features of absorption, storage or release of water (or solvent), gels have become essential in engineering applications, such as the development of superabsorbent materials, soilless agriculture, and tissue engineering and regeneration. Also, gels are key players for the design of flexible actuators, valves, and sensors. However, their generally weak mechanical performances and inherent difficulties in manufacturing and assembling limit their applications. Many efforts are devoted to overcoming the intrinsic fragility of gels (altogether improving their rigidity) by exploring original macromolecular topologies.
By designing hybrid gels with solid nanoparticles (NPs), we demonstrated that polymer adsorption onto NPs can be a simple and remarkably effective means for gel toughening, either in bulk by designing nanocomposite gels1 (NC gels) or at the interface2 (gel adhesion with NP solutions). Based on this concept, the goal of this project is to investigate the underlying local mechanisms at the vicinity of an advancing crack using the supersonic shear imaging (SSI) technique.
In materials science, it is well-known that maximizing the dissipative processes during crack propagation is essential in slowing crack propagation and to achieve efficient fracture toughening. Hence, fracture energy not only depends on the interfacial toughness, but more importantly, it depends on the energy that can be expended in a volume. Although various attempts to relate fracture conditions to linear viscoelasticity provided qualitative understanding, the extent of the dissipative volume still remains unclear.
We have demonstrated that the response of NC gels is highly time-dependent (controlled by the polymer network rearrangement at the NP surface). However, the time-dependence of fracture energy and mechanism(s) leading to changes in the dissipated volume remain unexplored so far. Recently, we pioneered the use of SSI for the assessment of NC gel viscoelastic properties3. By coupling SSI with conventional large strain mechanical tests, we expect to map the dissipative region of an advancing crack. The main advantages of using SSI for gel fracture are : (1) the ability to probe non-linear viscoelastic properties at high frequencies, (2) the capability for non-invasive mapping of processes at the gel surface and beyond. Identifying the significance of dissipation and the relevant parameters that enable the effective enhancement of the fracture energy is invaluable to guiding the design of gels with advanced mechanical responses4. At the interfaces of physics, mechanics, and chemistry, this project seeks to develop an innovative experimental methodology to meet the next challenges in the field of gel design together with developing the description of biological tissues in terms of elastic and dissipative component. This could provide clinicians a real added value in the framework of diagnosis and more generally to sharpen the description of biological tissues under osmotic and/or mechanical stresses
1 Time Dependence of Dissipative and Recovery processes in Nanohybrid Hydrogels. Rose, S ; Dizeux, A ; Narita, T ; Hourdet, D ; Marcellan, A / Macromolecules (2013)
2 Nanoparticle solutions as adhesives for gels and biological tissues. Rose, S ; Prevoteau, A ; Elziere, P ; Hourdet, D ; Marcellan, A ; Leibler, L. / Nature (2014)
3 Rheology over five orders of magnitude in model hydrogels : agreement between strain-controlled rheometry, transient elastography, and supersonic shear wave imaging. Gennisson, JL ; Marcellan, A ; Dizeux, A ; Tanter M. / IEEE Transactions On Ultrasonics Ferroelectrics &Frequency Control (2014)
4 Thermoresponsive Toughening with Crack Bifurcation in Phase-Separated Hydrogels under Isochoric Conditions. Guo, H ; Sanson, N ; Hourdet, D ; Marcellan, A / Advanced Materials (2016)
3i Aspects
This project is built to reinforce interdisciplinarity between two ESPCI labs. The SIMM lab is a soft matter lab, focused on physics, mechanics and chemistry and the Wave Physics for Medicine team from LANGEVIN Institute specialized in physics, biology and medicine. The first research aim is directly related to the field of material science. Current industrial applications of gels as load-bearing systems are essentially prospective. Recently, great improvements have been done in the design of tough gels. Gels with 70wt% of water can attain moduli and fracture energies as high as classical unfilled rubbers with the additional key benefit to having a low environmental impact. In parallel, this project presents an opportunity to develop the supersonic shear imaging (SSI) technology to assess the biomechanical properties of biological tissues. Although shear wave elastography is developed for quantifying and mapping in vivo tissue stiffness, recent efforts are made to use SSI to provide a cartography of both elastic and loss moduli, G’ and G”, respectively. This could provide clinicians a real added value in the framework of diagnosis (breast cancer, for example), and more generally to sharpen the description of biological tissues under osmotic and/or mechanical stresses. International collaborations can easily be envisaged from both partners of the project.
PhD supervisor(s) Alba MARCELLAN and Mickael TANTER (co-supervisor)
Présentation établissement et labo d’accueil
ESPCI Paris
The Hosting LabInspired by the soft matter concepts, the SIMM (UMR7615) laboratory combines competences – chemistry, physics and mechanics – to develop a comprehensive picture of links between macromolecular architectures (by using model systems) and their macroscopic properties. In that context, SIMM has gained an expertise during the last 10 years in designing gels by developing customized mechanical techniques optimized for characterizing gels. Despite a surge in publications, only a few groups have managed to couple such transdisciplinary skills. In 2016, members of the SIMM lab joined the Global Station for Soft Matter Program, an international laboratory serving to strengthen innovative research in the field of gels and their medical applications.The second research team, “Wave Physics for Medicine” (ERL INSERM U979), from the Langevin Institute, is involved in this project. The team consists of physicists experts in biomedical imaging using wave physics from the cellular level to organs. The group is an internationally recognized leader for the development of new biomedical imaging techniques, such as transient elastography, shear wave elastography, ultrafast echography, and more recently fUltrasound (functional ultrasound imaging for neurosciences). Currently, this team is actively promoting "multi-wave imaging", which leverages interactions between different types of waves in tissues.
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Profil du candidat
BS/BA, MS or equivalent degree (MS preferred) in Physics, Material Science or Physicochemistry. Excellence in past academic achievements. Preference will be given to students with experience in the following areas (but not limited to) : ultrasound imaging, rheology, mechanics or gel design. Looking for a highly motivated, autonomous, creative thinker with the ability to work in a highly multidisciplinary environment. Interpersonal and communication skills are essential.
Date limite de candidature
28/02/2018
Date de début de thèse
01/09/2018
Eléments à fournir pour la candidature
Applications must be submitted on the UPtoPARIS
More information is available in the "How to apply" section of the website.