This sample came from The Swedish School of Textile. It shrinks when heat is applied and it is not reversible. When knitted together with heat emitting thread, you can control the shape (shrink) of the textile dynamically. Only downside is that it is not reversible.
Plug and Wear sells a shrinking sewing thread that shrinks 30% in length when heat is applied to it (with an iron).
“This comes very handy to sew components on our textile . Just sew them normally and then put your pressing iron close to the back of the circuit. The thread will shrink and all components will firmly be connected to the textile perfboard.”