The parts list
Franziska Jehle and colleagues at the Max Planck Institute of Colloids and Interfaces examined five separate slimes made by the garden snail Cepaea nemoralis: for crawling, sticking, sealing the shell, resisting drying and defending itself. All five come out of the same two components. Collagen VI builds the structure, and calcium is added during secretion. The study appeared in the journal Science.[1]
The variable sits in how the second component is used rather than in the list itself. Collagen VI sets how dense the protein network is; calcium does two separate jobs. In wet slimes it behaves like a cross-linker that ties the network together, and in dry slimes it hardens as calcite. Jehle says the snail can specifically alter the properties of its mucus using the same basic building blocks.[1]
Why this matters to anyone who builds things
In industrial materials a new property is usually bought with a new component: an additive, a coating, a second polymer. That is exactly what makes a laminate or a blend hard to separate at end of life. Here two opposing behaviours, lubrication and adhesion, come out of the same pair.[1]
The adjustment appears to sit in the state of the calcium and the density of the network. Another possibility exists: control may rest in secretion timing, in water content, or in smaller proteins the study does not resolve. In that case the recipe would be harder to copy than the parts list suggests, and getting five functions out of a single formulation in a laboratory would be correspondingly harder.[1]
Can it be rebuilt?
Peter Fratzl, the institute's director and a co-author, points out that natural materials achieve enormous variety with just a few building blocks. That is a claim about design space, and its test is reproduction. A synthetic gel made from one protein network and one calcium carbonate source, switching between sliding and sticking according to the state of the mineral, would settle it.[1]
The signal to watch is therefore narrow and concrete: a published synthetic system that produces at least two of the five behaviours from a single formulation, with the switch controlled by the mineral alone. If such a system appears, a way of solving the separation problem in recycling without raising the component count becomes visible.[1]