Tag Archives: Université Pierre et Marie Curie

Spider webs inspire liquid wire

Courtesy University of Oxford

Courtesy University of Oxford

Usually, when science talk runs to spider webs the focus is on strength but this research from the UK and France is all about resilience. From a May 16, 2016 news item on phys.org,

Why doesn’t a spider’s web sag in the wind or catapult flies back out like a trampoline? The answer, according to new research by an international team of scientists, lies in the physics behind a ‘hybrid’ material produced by spiders for their webs.

Pulling on a sticky thread in a garden spider’s orb web and letting it snap back reveals that the thread never sags but always stays taut—even when stretched to many times its original length. This is because any loose thread is immediately spooled inside the tiny droplets of watery glue that coat and surround the core gossamer fibres of the web’s capture spiral.

This phenomenon is described in the journal PNAS by scientists from the University of Oxford, UK and the Université Pierre et Marie Curie, Paris, France.

The researchers studied the details of this ‘liquid wire’ technique in spiders’ webs and used it to create composite fibres in the laboratory which, just like the spider’s capture silk, extend like a solid and compress like a liquid. These novel insights may lead to new bio-inspired technology.

A May 16, 2016 University of Oxford press release (also on EurekAlert), which originated the news item, provides more detail,

Professor Fritz Vollrath of the Oxford Silk Group in the Department of Zoology at Oxford University said: ‘The thousands of tiny droplets of glue that cover the capture spiral of the spider’s orb web do much more than make the silk sticky and catch the fly. Surprisingly, each drop packs enough punch in its watery skins to reel in loose bits of thread. And this winching behaviour is used to excellent effect to keep the threads tight at all times, as we can all observe and test in the webs in our gardens.’

The novel properties observed and analysed by the scientists rely on a subtle balance between fibre elasticity and droplet surface tension. Importantly, the team was also able to recreate this technique in the laboratory using oil droplets on a plastic filament. And this artificial system behaved just like the spider’s natural winch silk, with spools of filament reeling and unreeling inside the oil droplets as the thread extended and contracted.

Dr Hervé Elettro, the first author and a doctoral researcher at Institut Jean Le Rond D’Alembert, Université Pierre et Marie Curie, Paris, said: ‘Spider silk has been known to be an extraordinary material for around 40 years, but it continues to amaze us. While the web is simply a high-tech trap from the spider’s point of view, its properties have a huge amount to offer the worlds of materials, engineering and medicine.

‘Our bio-inspired hybrid threads could be manufactured from virtually any components. These new insights could lead to a wide range of applications, such as microfabrication of complex structures, reversible micro-motors, or self-tensioned stretchable systems.’

Here’s a link to and a citation for the paper,

In-drop capillary spooling of spider capture thread inspires hybrid fibers with mixed solid–liquid mechanical properties by Hervé Elettro, Sébastien Neukirch, Fritz Vollrath, and Arnaud Antkowiak. PNAS doi: 10.1073/pnas.1602451113

This paper appears to be open access.

Observing silica microspheres leads to theories about schools of fish and human crowds

Researchers developing theories about the crowd behaviour of tiny particles believe the theories may have some relevance to macro world phenomena.

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From a March 9, 2016 news item on Nanowerk,

Crowds formed from tiny particles disperse as their environment becomes more disordered, according to scientists from UCL [University College London, UK], Bilkent University [Turkey] and Université Pierre et Marie Curie [France].

The new mechanism is counterintuitive and might help describe crowd behaviour in natural, real-world systems where many factors impact on individuals’ responses to either gather or disperse.

“Bacterial colonies, schools of fish, flocking birds, swarming insects and pedestrian flow all show collective and dynamic behaviours which are sensitive to changes in the surrounding environment and their dispersal or gathering can be sometimes the difference between life and death,” said lead researcher, Dr Giorgio Volpe, UCL Chemistry.

A March 9, 2016 UCL press release (also on EurekAlert), which originated the news item, expands on the theme,

“The crowd often has different behaviours to the individuals within it and we don’t know what the simple rules of motion are for this. If we understood these and how they are adapted in complex environments, we could externally regulate active systems. Examples include controlling the delivery of biotherapeutics in nanoparticle carriers to the target in the body, or improving crowd security in a panic situation.”

The study, published today in Nature Communications, investigated the behaviour of active colloidal particles in a controllable system to find out the rules of motion for individuals gathering or dispersing in response to external factors.

Colloidal particles are free to diffuse through a solution and for this study suspended silica microspheres were used. The colloidal particles became active with the addition of E. coli bacteria to the solution. Active colloidal particles were chosen as a model system because they move of their own accord using the energy from their environment, which is similar to how animals move to get food.

Initially, the active colloidal particles gathered at the centre of the area illuminated by a smooth beam which provided an active potential. Disorder was introduced using a speckle beam pattern which disordered the attractive potential and caused the colloids to disperse from the area at a rate of 0.6 particles per minute over 30 minutes. The particles switched between gathering and dispersing proportional to the level of external disorder imposed.

Erçağ Pinçe, who is first author of the study with Dr Sabareesh K. P. Velu, both Bilkent University, said: “We didn’t expect to see this mechanism as it’s counterintuitive but it might already be at play in natural systems. Our finding suggests there may be a way to control active matter through external factors. We could use it to control an existing system, or to design active agents that exploit the features of the environment to perform a given task, for example designing distinct depolluting agents for different types of polluted terrains and soils.”

Co-author, Dr Giovanni Volpe, Bilkent University, added: “Classical statistical physics allows us to understand what happens when a system is at equilibrium but unfortunately for researchers, life happens far from equilibrium. Behaviours are often unpredictable as they strongly depend on the characteristic of the environment. We hope that understanding these behaviours will help reveal the physics behind living organisms, but also help deliver innovative technologies in personalised healthcare, environmental sustainability and security.”

The team now plan on applying their findings to real-life situations to improve society. In particular, they want to exploit the main conclusions from their work to develop intelligent nanorobots for applications in drug-delivery and environmental sustainability that are capable of efficiently navigate through complex natural environments.

Here’s a link to and a citation for the paper,

Disorder-mediated crowd control in an active matter system by Erçağ Pinçe, Sabareesh K. P. Velu, Agnese Callegari, Parviz Elahi, Sylvain Gigan, Giovanni Volpe, & Giorgio Volpe. Nature Communications 7, Article number: 10907 doi:10.1038/ncomms10907 Published 09 March 2016

This is an open access paper.

Graphene and an artificial retina

A graphene-based artificial retina project has managed to intermingle the European Union’s two major FET (Future and Emerging Technologies) funding projects, 1B Euros each to be disbursed over 10 years, the Graphene Flagship and the Human Brain Project. From an Aug. 7, 2014 Technische Universitaet Muenchen (TUM) news release (also on EurekAlert),

Because of its unusual properties, graphene holds great potential for applications, especially in the field of medical technology. A team of researchers led by Dr. Jose A. Garrido at the Walter Schottky Institut of the TUM is taking advantage of these properties. In collaboration with partners from the Institut de la Vision of the Université Pierre et Marie Curie in Paris and the French company Pixium Vision, the physicists are developing key components of an artificial retina made of graphene.

Retina implants can serve as optical prostheses for blind people whose optical nerves are still intact. The implants convert incident light into electrical impulses that are transmitted to the brain via the optical nerve. There, the information is transformed into images. Although various approaches for implants exist today, the devices are often rejected by the body and the signals transmitted to the brain are generally not optimal.

Already funded by the Human Brain Project as part of the Neurobotics effort, Garrido and his colleagues will now also receive funding from the Graphene Flagship. As of July 2014, the Graphene Flagship has added 86 new partners including TUM according to the news release.

Here’s an image of an ‘invisible’ graphene sensor (a precursor to developing an artificial retina),

Graphene electronics can be prepared on flexible substrates. Only the gold metal leads are visible in the transparent graphene sensor. (Photo: Natalia Hutanu / TUM)

Graphene electronics can be prepared on flexible substrates. Only the gold metal leads are visible in the transparent graphene sensor. (Photo: Natalia Hutanu / TUM)

Artificial retinas were first featured on this blog in an Aug. 18, 2011 posting about video game Deus Ex: Human Revolution which features a human character with artificial sight. The post includes links to a video of a scientist describing an artificial retina trial with 30 people and an Israeli start-up company, ‘Nano Retina’, along with information about ‘Eyeborg’, a Canadian filmmaker who on losing an eye in an accident had a camera implanted in the previously occupied eye socket.

More recently, a Feb. 15, 2013 posting featured news about the US Food and Drug Administration’s decision to allow sale of the first commercial artificial retinas in the US in the context of news about a neuroprosthetic implant in a rat which allowed it to see in the infrared range, normally an impossible feat.

Get out your ‘haptic optical tweezers’

I’m about to have a paper published Scientists at l’Université Pierre et Marie Curie (France) have made it possible to touch objects at the microscale with a technique that  is distinctly different from the haptic microscopes used for work at the nanoscale . Microscopes designed for use at the nanoscale are haptic and have been since the beginning. By contrast, a standard microscope was designed as an optical device. From the Sept. 13, 2013 news item on ScienceDaily,

In a breakthrough that may usher in a new era in the exploration of the worlds that are a million times smaller than human beings, researchers at Université Pierre et Marie Curie in France have unveiled a new technique that allows microscope users to manipulate samples using a technology known as “haptic optical tweezers.”

Featured in the journal Review of Scientific Instruments, which is produced by AIP [American Institute of Physics] Publishing, the new technique allows users to explore the microworld by sensing and exerting piconewton-scale forces with trapped microspheres with the haptic optical tweezers, allowing improved dexterity of micromanipulation and micro-assembly.

This research required a mix of different experimental techniques and theoretical knowledge. Labs at the Institut des Systèmes Intelligents et de Robotique possessed expertise in both microrobotics and in haptics which were needed but the research team, as the project progressed, realized that they needed additional expertise in optics and vision, which was available at the university. …

The ability to use touch as a tool to allow exploration, diagnosis and assembly of widespread types of elements from sensors, microsystems to biomedical elements, including cells, bacteria, viruses, and proteins is a real advance for laboratories. These objects are fragile, and their dimensions make them difficult to see under microscope. If this tool can restore the sense of touch under microscopic operation, it will help not only efficiency but also expand scientific creativity, said Dr. Pacoret [Cecile Pacoret, a co-author of the study], adding that she and her team are excited about the possibilities.

You can find a citation and a link for the paper at the end of the ScienceDaily news item.