When you conjure up an image of hydrogels such as jellies, you may realize that hydrogels have intermediate property between solid and liquid. Hydrogels are Indeed solid, because they do not flow and we can bring them with our hands.

Because almost all hydrogels are formed from aqueous solution, the system becomes solid from liquid during the formation process of hydrogels. This transformation is called sol-gel transition or simply gelation.

Because hydrogels are liquid prior to the gelation, we can inject them using syringe, and mold them in any shape. On the other hand, after the gelation, we cannot inject or mold them. In the case that we need to mold hydrogels, the time required for gelation (gelation time) should be not too short. In the case that we want to stop bleeding, the gelation time should be short so that they do not flowing away. Thus, the gelation time should be controlled properly.

Fabrication of Tetra-PEG gel

In the case that hydrogels are formed in vivo, we need to guarantee the biosafety of pre-gel solution and gelation reaction. Furthermore, to administer hydrogels on the surface of tissue homogeneously, it is important to control the rheological properties of pre-gel solution. The control over the whole gelation process is important factor for the practical application. One of our purposes is the independent control of both gelation process and other physical properties of gels.