Gels-networks of polymer chains cross-linked together by either chemically or noncovalently. Gels have both solid and liquid like properties. They have ability to swell reversibly in solutions up to 1000 times by volume. Gels have applications in numerous fields, including food, chemical processing, pharmaceutical, biothechnology, agriculture, civil engineering and electronics. They used as soft actuators, drug delivery systems, selective membranes etc.

Example of swollen polymer gel.

Soft actuator made of charged polymer gel.

(Provided by P. Mather)