Interfacial Chemical Reactions To Construct Heterogeneous Composite Hydrogel Actuators

Hydrogels have been widely used in the field of flexible actuators due to their high elasticity and stimulus response.However,homogeneous structure of traditional photo-crosslinked hydrogels makes it difficult to achieve complex controllable actuation,and multiphase composite hydrogels face the problem of interface failure,which seriously limits the application range of hydrogel actuators.In this paper,the strong adhesion interface between hydrogel and substrate is constructed by using two kinds of interface crosslinking reactions to improve adhesion performance and break through the application bottleneck of hydrogel actuation:（1）Hydrogel/elastomer composite actuator with stimulus response performance was constructed based on interfacial photochemical crosslinking.The design includes chemical modification of the elastomer and in situ polymerization of hydrogel on the surface of the elastomer.Under the alternating action of moisture and near infrared light,the bidirectional bending drive of the composite driver can be realized,and the interface failure will not appear in the repeated deformation.（2）Based on electrochemically induced physical crosslinking reaction,the interface adhesion of hydrogel was realized,and the hydrogel composite actuators with stimulus response performance was constructed.The mechanical properties and adhesion interactions of hydrogels were improved by the migration of metal ions(Fe³⁺)generated by electrochemical reaction under the action of electric field and the formation of ion crosslinking network formed by coordination between metal ions(Fe³⁺)and functional groups in hydrogels.At the same time,the hydrogel with stimulus response performance was modular assembly,and the directional drive of the hydrogel actuator could be realized by adjusting the p H value of the environment.The research above provides a new idea for the construction of hydrogel actuator with strong adhesion interface,and broadens its application in flexible robots,sensors and other fields.