The results of the study are incredibly important for understanding the material properties of gels that are mixed into the likes of toothpaste and many other cosmetics to stabilise them.
Researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg and Heinrich Heine University Düsseldorf examined a model consisting of a gel made of a mixture of colloids - particles that are only a thousandth of a millimetre in size - and even smaller macromolecules known as polymers.
‘There must not be any loops in the system’
Before the liquid mixture becomes a gel, all of the particles can move freely. The colloids generally repel each other.
However, these scientists say if they get so close to one another than even the smallest polymers can no longer pass between them, they are forced even closer together.
This causes colloid chains to form. If these chains form a complex network across the whole system, it results in a gel - at least that was what researchers previously thought.
To the contrary, this research shows that the chains of particles must have a specific form in order to form a gel - they must be directed, which means that there must not be any loops in the system.
Imagine it like this: if you move through a system along a directed chain you travel only in one direction, whereas in a system with loops you would also have to go back on yourself at some points.
Directed chains give the system more stability than loops and are responsible for a gel's solid properties.