Polymer gels have been extensively studied since the discovery of volume phase-transition of a gel byTanaka. As a unique soft material, gels attract much attention and are tried to be applied for drug-delivery systgems, actuators or chemo-mechanical devices and so on. In particular, controlled-releaseof small molecules from a gel is now a subject of special interest. People are seeking the way to make use ofthe swelling/shrinking property of the gel accompanied by its phase-transition so that the mesh-size of polymerchain networks can be tuned.