Soft Matter Blog

A Hot Review from Tagliazucchi and Szleifer discussing macromolecular layers on nano-curved surfaces. Topics include the fast-growing field of polymer- and polyelectrolyte-modified nanopores and nanochannels, and the practical implications of introducing soft materials into nanofluidic devices.

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Stimuli-responsive polymers grafted to nanopores and other nano-curved surfaces: structure, chemical equilibrium and transport
Mario Tagliazucchi and Igal Szleifer
Soft Matter, 2012, 8, DOI: 10.1039/C2SM25777G

Spider silk has outstanding mechanical properties, and the study of this biomaterial can lead to the development of synthetic high performance fibers. However, there is still limited knowledge of how the structure of silk affects the mechanical properties.

Plaza and co-workers studied the microstructural changes of supercontracted major ampullate silk fibres during deformation, in our first Hot Paper. Two distinct regimes in the microstructural evolution were identified.

Flagelliform (Flag) silk was studied in our second Hot Paper by Lefèvre and Pézolet. Raman spectromicroscopy was used to characterize Flag silk fibers spun by three orb-weaving spiders in their native state. The structural data obtained provides a molecular basis for the tensile properties of these fibers.

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Relationship between microstructure and mechanical properties in spider silk fibers: identification of two regimes in the microstructural changes
Gustavo R. Plaza,  José Pérez-Rigueiro,  Christian Riekel,  G. Belén Perea,  Fernando Agulló-Rueda,  Manfred Burghammer,  Gustavo V. Guinea and Manuel Elices
Soft Matter, 2012, 8, 6015-6026, DOI: 10.1039/C2SM25446H

Unexpected β-sheets and molecular orientation in flagelliform spider silk as revealed by Raman spectromicroscopy
Thierry Lefèvre and Michel Pézolet
Soft Matter, 2012, 8, 6350-6357, DOI: 10.1039/C2SM25351H

The crystallization of a colloidal system in the presence of secondary nanoparticles is studied in this Hot Paper. This system acts as a model for the affect of impurities in crystallization processes, which are important in a number of applications. A novel strategy for the texture control of colloidal polycrystals, based on the addition of small amounts of nanoparticles (NPs) as dopants to a solidifying matrix is presented. The experiments were successfully reproduced with a variety of NPs of different kinds, demonstrating the robustness of the model.

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Grain refinement and partitioning of impurities in the grain boundaries of a colloidal polycrystal
Neda Ghofraniha,  Elisa Tamborini,  Julian Oberdisse,  Luca Cipelletti and Laurence Ramos
Soft Matter, 2012, 8, DOI: 10.1039/C2SM25488C

Polymer gels are soft solids with thermodynamically semi-open features which enables the solvents to flow in and out of the gels. The gel volume, therefore, can be coupled to other types of mechanical stimulus such as solvent flow and centrifugal force. This Hot Review focuses on experimental and theoretical studies on a rich variety of phenomena caused by the strain-driven volume change of gels.

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Volume of polymer gels coupled to deformation
Kenji Urayama and Toshikazu Takigawa
Soft Matter, 2012, Advance Article, DOI: 10.1039/C2SM25359C

This Hot Highlight describes recent developments in lipid vesicles encapsulating aqueous two-phase polymer solutions (ATPS). Aqueous phase separation in the closed environment of a lipid vesicles can be a model system for biological microcompartments within a cell. Studying ATPS-loaded vesicles may lead to a deeper understanding of membrane behavior and membrane processes in vivo.

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Lipid membranes in contact with aqueous phases of polymer solutions
Rumiana Dimova and Reinhard Lipowsky
Soft Matter, 2012, 8, 2409-2415, DOI: 10.1039/C2SM25261A

A wound dressing that guides cells close to the wound has been designed by scientists in Switzerland.

The dressing is made from polydimethylsiloxane and is etched with grooves, which enhance cell polarisatrion, migration speed and directionality.

The dressing makes wound healing faster and may prevent scar tissue forming. The dressing is also non-adhesive and controls cells in a ‘top down’ approach. Unlike current dressing, this one can be removed when the tissue is healed.

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Topography-mediated apical guidance in epidermal wound healing
Anastasios Marmaras,  Tobias Lendenmann,  Gianluca Civenni,  Davide Franco,  Dimos Poulikakos,  Vartan Kurtcuoglu and Aldo Ferrari
Soft Matter, 2012, Advance Article, DOI: 10.1039/C2SM00030J

The authors of this Hot paper model a steel ball falling freely through a solution of entangled wormlike-micelles. In non-Newtonian fluids such as this, objects are known to settle unsteadily. They report for the first time that spheres larger than a critical size undergo unsteady motion and show sustained, repeated bursts of oscillations superposed on a constant baseline velocity.

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Oscillatory settling in wormlike-micelle solutions: bursts and a long time scale
Nitin Kumar,  Sayantan Majumdar,  Aditya Sood,  Rama Govindarajan,  Sriram Ramaswamy and A. K. Sood
Soft Matter, 2012, 8, 4310-4313, DOI: 10.1039/C2SM25077B

Soft materials are very susceptible to surface instabilities, which can lead to wrinkiling, folding and creasing. These deformations and morphological instabilities are usually in response to environmental stimuli, and this stimulus-responsiveness makes them promising candidates for applications as intelligent materials. This hot review documents recent progress into the investigtation of surface wrinkling of soft materials, such as gels and biological tissues. 

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Mechanics of morphological instabilities and surface wrinkling in soft materials: a review
Bo Li ,  Yan-Ping Cao,  Xi-Qiao Feng and Huajian Gao
Soft Matter, 2012, 8, 5728-5745, DOI: 10.1039/C2SM00011C

Using solid fillers in an elastomeric matrix is a well-known method for improving the mechanical properties of elastomers. In this hot paper a silica-filled model elastomer was used to study the interparticle connections between the filler particles. It was found that the distance between the particles is a crucial parameter in the mechanics of materials, and was compared to the  range of polymer dynamics modification within the system.

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Solid particles in an elastomer matrix: impact of colloid dispersion and polymer mobility modification on the mechanical properties
Aurélie Papon,  Hélène Montes,  François Lequeux,  Julian Oberdisse,  Kay Saalwächter and Laurent Guy
Soft Matter, 2012,8, 4090-4096, DOI: 10.1039/C2SM06885K