New gel material can modify properties at will

November 6, 2012
Modifying properties at will
© Giuseppe Foffi/EPFL SB ITP GR-FO

Controlling and modifying at will the transparency, electrical properties, and stiffness of a gel - such are the promises of a new discovery by researchers supported by the Swiss National Science Foundation (SNSF). This marks an important step for materials used in healthcare, high-tech, and the cosmetics industry.

At the mention of gel, we immediately imagine extravagant hairstyles. In fact, this material is hiding everywhere: from contact lenses to ink, from sensors to medical electrodes and even . Their ultra-absorbent properties, flexibility, and grip make them appealing to researchers and manufacturers. They consist of a network of solids that can retain up to 99% of liquid while maintaining their shape. EPFL researchers have just published how to combine two gels in such a way that they can monitor and change, almost at will, the properties of the new combined material.

Involved in research on lens transparency, Giuseppe Foffi had the idea to transpose his research to gels in general. In the case of the eye, this SNSF Professor highlighted how the mixture of two proteins with very specific characteristics rendered the organ transparent. Applied to gels, this method can predict how the two materials will aggregate to form a new one.

Work undertaken in Cambridge by Erika Eiser and his group has pro-duced a material that researchers have named "bigel". The researchers managed to create it so quickly by combining with nanoparticles, a technique in which they are specialized. The DNA can be connected with different particles to produce gels with various pre-determined properties.

By varying the size of the network of "bigel" particles on the , it is possible to adjust light in a controlled manner. The physicists can determine to what light the gel is sensitive, by becoming more or less opaque. This is an interesting property in the field of photonics, which seeks to modulate, amplify, or filter light transmissions. The same type of plasticity is also possible for electrical particles.

Another interesting characteristic of "bigels" is their reversibility. Just heat them to separate the components. It is enough to see the particular way that particles adjust to obtain other features, for example optics, from the same compounds. It is possible to have materials whose properties are dependent on temperature.

This discovery opens the door to a great deal of applications, for example, by associating molecules with specific electromagnetic properties, but also by altering the geometry of the particles network. "We could apply these methods to a wealth of materials other than , foams or inks," says Giuseppe Foffi. To explore this new area, the researcher must expand from the micro- to the nanometric level. He also wants to explore "trigels" and other "polygels."

Explore further: Fluid cathedrals: Gels under the microscope

More information: Francesco Varrato, Lorenzo Di Michele, Maxim Belushkin, Nicolas Dorsaz, Simon H. Nathan, Erika Eiser and Giuseppe Foffi (2012). Arrested demixing opens novel route from gels to bigels. Proceedings of the National Academy of Sciences (PNAS): doi: 10.1073/pnas.1214971109

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1 / 5 (2) Nov 06, 2012
Gels are incredibly important to science, for although few realize it, there is a very longstanding debate in cell biology over them. It has been claimed by Gilbert Ling -- and more recently, Gerald Pollack -- that the cytoplasm is not an aqueous solution, but instead a gel. Few seem to realize it, but the imaging technique of the MRI was initially hypothesized based upon the ability of gels to structure the water within them.

The debate is incredibly important, because gels can *naturally* induce ionic gradients. This is a major blow to the pump-and-channel paradigm, for it suggests a far more efficient way for the body to maintain the observed ionic gradients across cell membrane walls.

Gerald Pollack's incredible book, Cells, Gels and the Engines of Life, covers the debate in great detail, and at a level which most laypeople can understand. It doesn't get complicated until the very end, by which point the layperson already understands the debate.
not rated yet Nov 07, 2012
Since many cells have an internal network called a cytoskeleton, their interiors could be considered to be somewhat gel-like. And it's quite possible that by attaching differently charged or polarized molecules to different regions of this scaffold, it could achieve some sort of electrical field gradient leading to an ionic gradient. But this is kind of situation will quickly lead to a static, dead state as all mobile ions would move until they find positions that quench as much of the gel's field as possible. The flaw in your stupid theory is that you've spent absolutely no time thinking about why the electric field is there at all. The electric field (or more precisely chemiosmotic potential) is there to help drive things across the cell membrane (whether to generate ATP, or to import nutrients, expel waste molecules, or transport signals), and in your failure scenario, once enough things have gotten across, they'll neutralize your gel field and the whole thing will stop dead.
not rated yet Nov 07, 2012
The cell needs to actively transport stuff across the membrane to maintain the chemiosmotic potential, using those pumps you blithely dismissed. And about those pumps and channels - many biologically-produced toxins' modus operandi is to block one of these, which makes the toxins quite useful to study the pumps and channels. It's a very rich and well-studied field. The pumps and channels exist, and their mechanisms of action are being elucidated. So another thing your stupid theory has failed to do is explain why these things exist.

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