Micro hydrogels: preparation, properties, and applications.

A micro hydro-gel is a submicron- or micron-sized network polymer particle that is insoluble in water but highly swellable. This review presents the following topics: preparation, properties, and applications of micro hydrogels. First, two types of preparation methods for micro hydrogels are presented: (i) particle-forming polymerization and (ii) molecular assembly of polymer chains dissolved in water. Next, the characteristic properties of micro hydrogels are discussed. Finally, the applications of micro hydrogels are reviewed, with special emphasis on environmentally sensitive optical/photonic, biological/biomedical, and chemical applications. This review is not comprehensive, but is rather a "mini-review" primarily focused on results obtained in the author's laboratories.