Soft Matter Blog

Professor Marshall Stoneham

21 Feb 2011

On Friday (18th February 2011), I received an email from the Institute of Physics (IOP). It informed me that the President of the IOP, Professor Marshall Stoneham FRS CPhys FInstP, had sadly passed away. Prof. Stoneham had a very successful career in academia, publishing and in industry. Most recently he worked at the London centre for Nanotechnology and University College London, where he was the Emeritus Massey Professor of Physics

In December I attended a talk by Prof. Stoneham at the CMMP10 conference in Warwick. His talk was well attended and his style engaging. The talk titled ‘Where physics meets biology’, discussed (amongst other things) how quantum mechanics could be used to explain how humans smell. His proposal was that receptors in the nose are actuated by electron tunnelling from a donor to an acceptor mediated by the odorant molecule.

Each odorant has its own vibrational frequency. When the vibrations of the odorant cause electrons in the nasal receptors to tunnel between energy states, a nerve signal is sent to the brain and the smell detected. Different vibrational frequencies are detected by different receptors. Since different smells have different frequencies, each odorant smells different. This model termed the ‘swipe card’ model allows receptors to ‘read’ an odorant molecule by detecting its vibrational spectrum along with matching its size and shape. “The shape must be good enough, but it is something else that carries the decisive information”. The results were published in Phys. Rev. Lett. doi=10.1103/PhysRevLett.98.038101.

Prof. Stoneham was the author of over 500 papers and a number of books on a wide range of subjects from biology to quantum computing and from nuclear safety to self-organisation. He was the recipient of the Gutrine gold medal of the IOP in 2006 for his wide-ranging theoretical work on defects in solids and the Royal Society’s Zeneca prize in 1995. Marshall Stoneham will be greatly missed by the physics community.

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Designer foods

21 Feb 2011

By Vibhuti Patel, Deputy Editor.

The way that we digest fat could be controlled by food design, providing potential health benefits, according to scientists from Australia.

Fat is an essential part of our diet, but too much of it can lead to problems such as heart disease and obesity. The digestion of fat is also involved in triggering the hormone signals that tell us whether or not we are full. Reducing fat intake in meals is often negated by overeating, so designing food that controls fat absorption is of great interest.

Micrographs showing structural changes occurring in the emulsion immediately after preparation (left), 30 minutes after incubation at pH 1.9 in simulated gastric fluid (middle) and 30 minutes after subsequent incubation at pH 6.8 in simulated intestinal fluid

Researchers at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Food and Nutritional Sciences designed fat emulsions using different surfactants, including protein, phospholipids and common food additives, and monitored how their structures changed during simulated digestion. They also gave the emulsions in a drink form to healthy volunteers and monitored blood triglyceride levels, which give an indication of how the fat is being digested by the body.

To view the full Chemistry World article, please click here: Designer foods

Link to journal article

Impact of gastric structuring on the lipolysis of emulsified lipids
Matt Golding, Tim J. Wooster, Li Day, Mi Xu, Leif Lundin, Jennifer Keogh and Peter Clifton, Soft Matter, 2011
DOI: 10.1039/c0sm01227k

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Hot Article on emerging area: biomaterials that mimic and exploit protein motion

20 Feb 2011

By Serin Dabb, Deputy Editor.

An excellent overview of an emerging strategy for synthesising hydrogels with more specific bio-responsiveness. Known protein motions are used as building blocks for synthetic dynamic materials, exploiting the conformational changes in proteins in response to specific biochemical triggers. Potential applications include drug delivery and bio-sensing.

Read the article for free here until March 18. William L. Murphy, Soft Matter, 2011, (Advance Articl3), DOI: 10.1039/C0SM01351J, Emerging Area.

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Two Hot Articles: ‘Nanofluidic networks created and controlled by light’ and ‘Cluster theory of Janus particles’

18 Feb 2011

By Russell Johnson, Development Editor.

Nanofluidic networks created and controlled by light. Nanofluidic networks have been fabricated in an oil-in-water emulsion by a team from the UK. In this hot paper, the authors demonstrate the principles required to create networks of micron-sized reactors connected by conduits less than 100 nm in diameter and to transfer reagents between them, entirely with lasers. These networks form a platform for chemistry on the attolitre scale and could open a path to controlled chemical reactions between single molecules the team claim. (Soft Matter, 2011, DOI:10.1039/C0SM01183E Advance Article)

Graphical abstract: Nanofluidic networks created and controlled by light

Cluster theory of Janus particles. A cluster theory for the vapor of Janus fluid has been constructed by a team from Italy and South Africa. The team say that main idea behind the present approach is to consider the vapor phase as formed by clusters, containing an increasing number of particles, that are weakly interacting among each other so that simple fluid models—such as ideal gas or hard spheres—can be used to mimick their physical properties. (Soft Matter, 2011, DOI:10.1039/C0SM00995D Advance Article)

Read both articles for free until 18th March.

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Hot Article: Cyclohexasilane-Liquid precursor for electronics

18 Feb 2011

By Serin Dabb, Deputy Editor.

Researchers have overcome solubility issues with cyclohexasilane by encapsulating it in copolymer micelles. The silane exhibits a stable host-guest interaction with the amphiphilic invertible polymers. Liquid precursors, such as cyclohexasilane are important for manufacturing electronic devices, similar to the ink component in inkjet printing.

Read the communication free here until 18 April. Ananiy Kohut, Xuliang Dai, Danielle Pinnick, Douglas L. Schulz and Andriy Voronov, Soft Matter, 2011, (Advance Article), DOI: 10.1039/C0SM01337D, Communication

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The potential of microfluidics

14 Feb 2011

By Katherine Thomas, Web Writer.

From top to bottom: Cholesteric particles formed via microfluidics. Flow-focusing microfluidic device. Gel emulsion in a channel. Fluorescence image of a dye-containing gel emulsion.

This week I attended a talk at the MPI for Dynamics and Self-Organisation in Goettingen, Germany by Nicolas Bremond from the EPSCI, Paris. The talk was titled “Microfluidic investigations of the destabilisation of emulsions via coalescence”. Nicolas discussed the use of microfluidic devices to study coalescence of emulsion droplets in the absence and presence of an ac electric field. The results have been published in Physical Review Letters and in the Journal of Fluid Mechanics.

In the absence of an electric field, a series of moving pairs of droplets in a microfluidic device were created. A widening of the channel, and therefore slowing of the fluid, was used to force the droplets together. Monitoring of the separation of the droplets showed that coalescence occurred just after closest proximity i.e. when they were separating. Nicolas believes that the separation of the droplets momentarily reduces the fluid pressure between the droplets, causing the high-pressure water in the droplets to burst through the barrier.

Amongst many of the movies shown in the talk was this one, which I have found on the web. It shows that this coalescence mechanism can also trigger coalescence in neighbouring droplets. This mechanism could perhaps be responsible for the clumping of industrial emulsion droplets.

My favourite video of the talk was one showing the behaviour of the emulsion droplets under an applied ac electric field. When the ratio of the radius of the droplet to the channel width is equal to 0.8 the droplets can be made to kiss each other; they come into contact with each other before separating again. On separation deformation of the droplets is observed. Unfortunately I haven’t found a video of this online, but a sequence of images can be seen in the Physical Review Letters paper.

Although not mentioned in the talk, Nicolas has also recently had his paper Formation of liquid-core capsules having a thin hydrogel membrane: liquid pearls published in Soft Matter.

Microfluidics offers an interesting method for studying the coalescence of emulsions under flow. However, this is not its only application as seen in the latest issue and advance articles of Soft Matter. Shashi Thutupalli et al. (doi:10.1039/c0sm00312c) demonstrate the use of microfluidics to self-assemble surfactant bilayer networks in water-oil emulsions. These bilayer membranes display a range of different electrical behaviours, which could be exploited to create wet circuitry. Formation of emulsions in this way, offers a feasible approach to construct complex devices out of molecular-sized components via controlled self-assembly.

Sara Abalde-Cela et al. demonstrate the use of a flow-focusing microfluidic device to form highly mono-disperse plasmonic agarose beads containing silver nanoparticles in their paper doi:10.1039/c0sm00601g, while Daniel Wenzlik et al. used microfluidics to prepare cholesteric liquid crystal particles from cellulose derivatives doi:10.1039/c0sm01368d.

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Hot Article: Lipid Membrane Fushion

14 Feb 2011

By Serin Dabb, Deputy Editor.

A novel fusion assay based on pore-spanning membranes has overcome the drawbacks of black lipid- and solid supported-membranes. This assay was able to monitor the calcium ion mediated fusion of lipid membranes, an important process in biology.

Scanning ion conductance microscopy investigated the change in morphology of the pore membrane after coating of the pore holes by the lipids.

Read the article for free here until Marth 11.

Ines Höfer and Claudia Steinem, Soft Matter, 2011, (Advance Article), DOI: 10.1039/C0SM01429J, Communication

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Hot Article: How do mechanical forces shape cells and their organelles?

14 Feb 2011

By Serin Dabb, Deputy Editor.

Researchers show that the spherical harmonics parameterization (SHP) method reliably calculates vesicle and cell morphology. Most importantly, SHP calculated the shape of red blood cells (RBC), reproducing the slightly out-of-plane spicules observed experimentally for echinocytes (crenated RBCs).

Read the article here, for free until 11 March: Khaled Khairy and Jonathon Howard
Soft Matter, 2011, (Advance Article), DOI: 10.1039/C0SM01193B, Paper

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A trio of Soft Matter Hot Articles

11 Feb 2011

By Russell Johnson, Development Editor.

Self-assembly of cellulose nanofibrils by genetically engineered fusion proteins. The team led by Markus Ben Linder describe how genetic engineering is used to design proteins that have “smart” functionalities that allow directed self-assembly of cellulose nanofibrils for the control of nanostructures in soft materials.

Suvi Varjonen, Päivi Laaksonen, Arja Paananen, Hanna Valo, Hendrik Hähl, Timo Laaksonen and Markus Ben Linder, Soft Matter, 2011, DOI:10.1039/C0SM01114B (Advance Article)

Nucleation of colloidal crystals on configurable seed structures. This hot paper shows the topology of the initial hard sphere nucleus determines the morphology of the crystal. The team led by A. van Blaaderen claim that the reported results explain the complex crystal morphologies observed in experiments on hard spheres.

M. Hermes, E. C. M. Vermolen, M. E. Leunissen, D. L. J. Vossen, P. D. J. van Oostrum, M. Dijkstra and A. van Blaaderen, Soft Matter, 2011, DOI: 10.1039/C0SM01219J (Advance Article)

Molecular dynamics and biaxiality of nematic polymers and elastomers. In this paper the authors study the origins of phase biaxiality in nematic polymers and elastomers to gain insight into the relation of molecular dynamics and biaxiality. The team report that broad biaxial nematic phases were found for liquid crystalline polymers in all conventional attachment geometries.

Felicitas Brömmel, Werner Stille, Heino Finkelmann and Anke Hoffmann, Soft Matter, 2011, DOI: 10.1039/C0SM01116A (Advance Article)

Read all of the papers for free until the 11^th March.

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Themed issue: International Soft Matter Conference 2010

10 Feb 2011

By Russell Johnson, Development Editor.

Soft Matter issue 4 was published as a themed issue with the International Soft Matter Conference 2010. Juan Colmenero, Dieter Richter and Roque Hidalgo-Alvarez were the guest editors. You can read their editorial here:

The front cover features Electrostatic-driven pattern formation in fibers, nanotubes and pores by Monica Olvera de la Cruz and co-workers.

Highlighted on the inside front cover is Complex plasma—the plasma state of soft matter by Manis Chaudhuri, Alexei V. Ivlev, Sergey A. Khrapak, Hubertus M. Thomas and Gregor E. Morfill which was selected as a Hot Article.

You can read the full themed issue here.