Gel mixture lets you hide a secret message in goo

A new method for mixing gels lets you hide secret messages in pools of unassuming goo, but it could also help create artificial spines.

Gels are made through a process called polymerisation, in which small molecules known as monomers join together in a tangled network. This makes mixing two gels while retaining their individual properties difficult, as the two different monomers end up combined in a single network. One solution is to polymerise the two gels first and then combine them, but that leads to a weak join between the two materials.

Now chemists at the University of Maryland have a better idea. It turns out that thickening the gel monomers with small particles of clay before polymerisation prevents them from mixing together while also providing a strong and seamless join.

The team demonstrated their new method by writing the letters "UMD" in one gel and surrounding them with another in a Petri dish, resulting in a smooth clear disc with no letters visible. The message is only revealed when viewed through polarising lenses, as the two gels polarise light differently. Another version of the same experiment using different gels only revealed the message when the disc was heated.

Hiding message isn't the real aim of the research, however, as hybrid gels have a number of other uses. Gels are currently used as scaffolding for growing tissue from stem cells, such as a new windpipe, and combined gels could be used to create mixes of different tissues. They could also replicate other organic materials that are known to be mixtures of gel-like substances, such as spinal discs.