We show the fibrous protein fibrin can serve as biocompatible glue with which to bind synthetic cationic or anionic hydrogels together. Both the bonding to and detachment from the hydrogels by fibrin (gelation and degradation, respectively) proceeded enzymatically under physiological conditions. We built a hydrogel-based actuator to demonstrate the method. (C) 2014, The Society for Biotechnology, Japan. All rights reserved.