Microgels' behavior under scrutiny

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

2013-04-30

(Press-News.org) 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.

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

For more information, please visit http://www.epj.org

The full-text article is available to journalists on request. END

ELSE PRESS RELEASES FROM THIS DATE:

The underground adventures of the Mediterranean frog Rana iberica

2013-04-30

Do frogs live underground? The answer is yes, some amphibians, such as salamanders and frogs have been often reported to dwell in subterranean habitats, some of them completely adjusted to the life in darkness, and others just spending a phase of their lifecycle in an underground shelter. Up until 2010, however, no one suspected that the Mediterranean anuran frog Rana iberica - commonly known as Iberian brown frog and usually found in streams - also participates in underground adventures. A new study published in the open access journal Subterranean Biology confirms the ...

Saturn's youthful appearance explained

2013-04-30

As planets age they become darker and cooler. Saturn however is much brighter than expected for a planet of its age - a question that has puzzled scientists since the late sixties. New research published in the journal Nature Geoscience has revealed how Saturn keeps itself looking young and hot. Researchers from the University of Exeter and the Ecole Normale Supérieure de Lyon found that layers of gas, generated by physical instability deep within the giant planet, prevent heat from escaping and have resulted in Saturn failing to cool down at the expected rate. Professor ...

Spanish lake found with the oldest remains of atmospheric contamination in southern Europe

2013-04-30

Atmospheric contamination due to heavy metals is currently a severe problem of global proportions, with important repercussions in public health. However, this type of pollution is not a recent fact and can even be detected during pre-historic times. A team of scientists, which includes scientists from the Andalusian Institute of Earth Sciences and the University of Granada, has discovered evidence of atmospheric pollution caused by lead. This evidence was found in a lagoon in Sierra Nevada (Granada), at an altitude of 3,020 m. The pollution comes from metallurgical activities, ...

Zebrafish study suggests that vitamin B2 (riboflavin) is an antidote to cyanide poisoning

2013-04-30

With the remains of a recent lottery winner having been exhumed for foul play related to cyanide poisoning, future winners might wonder what they can do to avoid the same fate. A new report in The FASEB Journal involving zebrafish suggests that riboflavin, also known as vitamin B2, may mitigate the toxic effects of this infamous poison. In addition, the report shows that zebrafish are a viable model for investigating the effects of cyanide on humans. As with any research involving animal models, these findings are preliminary until thoroughly tested in clinical trials. ...

1 step closer to a quantum computer

2013-04-30

A quantum computer is controlled by the laws of quantum physics; it promises to perform complicated calculations, or search large amounts of data, at a speed that exceeds by far those that today's fastest supercomputers are capable of. "You could say that a quantum computer can think several thoughts simultaneously, while a traditional computer thinks one thought at a time," says Weimin Chen, professor in the Division of Functional Electronic Materials at the Department of Physics, Chemistry and Biology at LiU, and one of the main authors of the article in Nature Communications. A ...

Synthetic derivatives of THC may weaken HIV-1 infection to enhance antiviral therapies

2013-04-30

A new use for compounds related in composition to the active ingredient in marijuana may be on the horizon: a new research report published in the Journal of Leukocyte Biology shows that compounds that stimulate the cannabinoid type 2 (CB2) receptor in white blood cells, specifically macrophages, appear to weaken HIV-1 infection. The CB2 receptor is the molecular link through which the pharmaceutical properties of cannabis are manifested. Diminishing HIV-1 infection in this manner might make current anti-viral therapies more effective and provide some protection against ...

Intervention can prevent PPD in adolescents

2013-04-30

By targeting the factors that may play a significant role in the development of postpartum depression (PPD) in adolescent mothers, researchers at Women & Infants Hospital of Rhode Island believe they have found a way to prevent it. The team – led by Maureen G. Phipps, MD, MPH, interim chief of obstetrics and gynecology and director of the Division of Research at Women & Infants, and Caron Zlotnick, PhD, of the hospital's Center for Women's Behavioral Health – recently published "Randomized controlled trial to prevent postpartum depression in adolescent mothers" in the ...

Shifting the burden of recycling

2013-04-30

Over the past two decades governments around the world have been experimenting with a new strategy for managing waste. By making producers responsible for their products when they become wastes, policy makers seek to significantly increase the recycling—and recyclability—of computers, packaging, automobiles, and household hazardous wastes such as batteries, used oil motor, and leftover paint—and save money in the process. This strategy, known as extended producer responsibility (EPR), is the subject of a new special feature in Yale University's Journal of Industrial ...

Study finds possible alternative to bariatric weight loss surgery

2013-04-30

CINCINNATI – An experimental procedure successfully tested in obese laboratory rats may provide a less-invasive alternative to bariatric weight-loss surgery, researchers report online in Endocrinology. Scientists at Cincinnati Children's Hospital Medical Center used a catheter to re-direct the flow of bile from the bile duct into the small intestine, producing the same metabolic and weight-loss benefits as bariatric surgeries such as gastric by-pass. They named the procedure bile diversion, or BD. "This may lead to novel ways to treat obesity related conditions," said ...

Cruise tourists spend less

2013-04-30

More and more cruise ships visit the fjords of Western Norway. But cruise tourists only spend a fraction of what other tourists spend. Over the past few years, the overall number of tourists to Western Norway has declined slightly. But one group of tourists is steadily rising: the cruise ship passenger. However, the cruise ship industry matters little to the tourism industry onshore. The average camping tourist leaves behind twice as much as the average cruise ship tourist. And this even when one excludes costs and taxes for camping, says Professor Svein Larsen of the ...

Crystal L. Mackall, MD, FAACR, recognized with the 2025 AACR-Cancer Research Institute Lloyd J. Old Award in Cancer Immunology

A novel strategy for detecting trace-level nanoplastics in aquatic environments: Multi-feature machine learning-enhanced SERS quantification leveraging the coffee ring effect

Microgels' behavior under scrutiny

ELSE PRESS RELEASES FROM THIS DATE:

LAST 30 PRESS RELEASES: