Surprising new behaviour in gels
"Imagine putting a brick next to a stone and finding that the brick was moving into the stone, and vice versa" - this is how Professor David Smith of the University of York describes his latest piece of research into gels.
Gels - mixtures of solid and liquid - are important materials in everyday life, with applications as wide-ranging as personal care products, lubrication, drug delivery systems and biomaterials.
"We have, for some time, been fascinated with the characteristics and applications of gel-type materials", says David. "This fascination is partly child-like - who hasn't, rather like my five year old, played with jelly and wondered about why it behaves the way it does? This is what we are doing in this paper, but by carefully controlling the structures of our gels, and understanding what happens on a molecular level, we can gain a more detailed understanding and can observe new forms of behaviour."
David's gels contain a solid-like network that is assembled within a liquid-like phase, holding the whole material together. It had previously been assumed that the solid-like network was fixed and unable to move, but in this new work, David and his PhD student Jorge Ruiz-Olles have shown that this is not always the case.
"Our gels exchange their 'solid-like' components with one another", he said. "Putting two gels next to each other, and finding that all of the solid parts could slowly diffuse into one another was very surprising to us." So surprising, in fact, that he describes it as like seeing a brick move into a stone.
"We suspect this kind of behaviour may actually be quite rare in gels", he says. "In the paper we suggest how other authors may be able to identify whether their gels behave in the same way, so that we can work out just how general this new kind of mobility in gels actually is."
This behaviour has serious real-world applications. "If the solid-like networks of gels can move", says David, "this opens up ways in which gels can easily heal or adapt themselves. This opens the longer-term possibilities of developing smart soft materials for use in components that can heal their solid-like networks if they suffer damage. Alternatively this general principle could help further develop gels as biomaterials that can effectively adapt and interact their network structures when brought into contact with biological tissue."
Source: Royal Society of Chemistry