EPJ E Highlight - Microgels’ behaviour under scrutiny

Set of measured velocity profiles with Carbopol microgel.

A new study explores the counter-intuitive behaviour of a microgel composed of soft polymer blobs

Being a physicist offers many perks. For one, it allows an understanding of the substances ubiquitous in everyday industrial products such as emulsions, gels, granular pastes or foams. These are known for their intermediate behaviour between fluid and solid. Paint, for example, can be picked up on a paintbrush without flowing and spread under the stress of the brush stroke like a fluid. Baudouin Geraud and colleagues from the Light Matter Institute at the University of Lyon, France, have studied the flow of a microgel confined in microchannels. They have shown, in a study just published in EPJ E, that its behaviour under confinement differs from predictions based on standard theories. Indeed, its molecules are not only subjected to local forces, but also to neighbouring forces that affect its flow.

The authors chose to study the influence of confinement on the flow of a polymer microgel named Carbopol. It is made of jammed acrylic acid polymer blobs, typically a few microns in size, dispersed in water. For the first time, they explored whether this network of polymers can have an impact on the flow of this microgel when confined under a large range of pressure differentials and fluid movement speeds.

They relied on techniques including an approach constraining the complex fluid in sub-millimeter scale microchannels, known as microfluidic. They also used a high-resolution particles’ speed measurement method called Tracking Particle Velocimetry and studied the flow response to an external force.

Geraud and colleagues confirmed, for the first time in a microgel, that the flow properties at a local point do not depend only on the local force but also on the dynamics of its vicinity. This has previously been shown in concentrated emulsions, granular materials and foams under confinement.

Confined flows of a polymer microgel. B. Geraud, L. Bocquet and C. Barentin (2013), European Physical Journal E 36: 30, DOI 10.1140/epje/i2013-13030-3

This was our first experience of publishing with EPJ Web of Conferences. We contacted the publisher in the middle of September, just one month prior to the Conference, but everything went through smoothly. We have had published MNPS Proceedings with different publishers in the past, and would like to tell that the EPJ Web of Conferences team was probably the best, very quick, helpful and interactive. Typically, we were getting responses from EPJ Web of Conferences team within less than an hour and have had help at every production stage.
We are very thankful to Solange Guenot, Web of Conferences Publishing Editor, and Isabelle Houlbert, Web of Conferences Production Editor, for their support. These ladies are top-level professionals, who made a great contribution to the success of this issue. We are fully satisfied with the publication of the Conference Proceedings and are looking forward to further cooperation. The publication was very fast, easy and of high quality. My colleagues and I strongly recommend EPJ Web of Conferences to anyone, who is interested in quick high-quality publication of conference proceedings.

On behalf of the Organizing and Program Committees and Editorial Team of MNPS-2019, Dr. Alexey B. Nadykto, Moscow State Technological University “STANKIN”, Moscow, Russia. EPJ Web of Conferences vol. 224 (2019)

ISSN: 2100-014X (Electronic Edition)

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