UMR 5672

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Abstract

The effects of high-power ultrasound on colloidal gels? / Elastic thin sheets, origami and the pizza theorem
When Mar 29, 2019
from 12:45 PM to 01:45 PM
Where Room R115
Attendees DAGES Noémie / ANDRADE Ignacio
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Noémie DAGES : The effects of high-power ultrasound on colloidal gels?

Low-intensity ultrasound is widely used to probe and image biological tissues. Yet, ultrasound can also be used at high power to destroy nodules or burn tumors. We try totranspose and understand the latter effects in soft matter. We first show that high-power ultrasound softens colloidal gels. Upon applying ultrasound at 45kHz for a few tens of seconds on various gels in arheometer, we find that the elastic modulus of the gel is weakened and that its fluidization is fastened. As ultrasound is turned off, the gel recovers its elasticity. To investigate this process at the micron scale, we then probe the gel under ultrasound with small-angle X-ray scattering and with microscopy.

Ignacio ANDRADE : Elastic thin sheets, origami and the pizza theorem

How the elastic response of an object is modified when one of its dimensions is much smaller than the others, e.g. a piece of paper? What happens when we fold a piece of paper, crumple it or try to do some origami? What can knowing this be useful for?, and how is all this related to the way we eat pizza? In this seminar I will discuss some topics related to elasticity of thin sheets, its applications and some results of my PhD work.