  Cosmic large-scale structures, animal flocks, and living tissues are
non-equilibrium organized systems created by dissipative processes. Despite the
uniqueness, the realization of dissipative structures is still difficult.
Herein, we report that a network formation process in a dilute system is a
dissipative process, leading to percolation induced gel-gel phase separation
(GGPS) in a prominent miscible polymer-water system. The dilute system, which
forms a monophase structure at the percolation threshold, eventually separates
into two gel phases in a longer time scale as the network formation progresses.
The dilute hydrogel with GGPS exhibits an unexpected mesoscale co-continuous
structure and induces adipose growth in subcutaneous. The formation mechanism
of GGPS and a cosmic large-scale structure is analogous, in terms of attractive
interactions in a diluted system driving phase separation. This unique
phenomenon unveils the possibility of dissipative structures enabling advanced
functionalities and will stimulate research fields related to dissipative
structures.
