Shrinking-induced instability in gels

Polymer gels can undergo a volume phase transition (either continuous or discontinuous) when an external condition such as temperature or solvent composition is altered [1, 2]. This phase transition is either a shrinking or a swelling. We investigate the instability of a tubular uid gel after shrinking. When gels are immersed in a solvent, the polymer network undergoes a di usion inducing an osmosis pressure through the gel. A bubble and a bamboo pattern were observed under such conditions (E. sato-Matsuo and T. Tanaka, Nature 358 482 (1992)). In this paper we investigate this pattern formations as a mechanical instability.