Small functional hydrogels with big engineering applications

Hydrogels are crosslinked water-retaining network formed by hydrophilic natural or synthetic polymers. Traditional hydrogels usually are limited by the swelling performance and poor mechanical strength so that not enable to applied in engineering fields. Functional hydrogels possessing tailorable features such as superwettability, strong adhesion, enhanced mechanical strength and conductivity have attracted tremendous interest due to the promising application in functional coating materials, biomedicine, flexible electronics. In this review, the specific design strategies to the corresponding tailorable features of functional hydrogels, such as surface structure construction or chemical modification to obtain the superwettability, are highlighted and classified. Then the applications of functional hydrogels are categorized into three engineering application parts: environment, electronic and biomedicine. More important, the latest advance on the engineering application of functional hydrogels, including oil/water separation, wastewater treatment, flexible electronics, sensor, wound healing and drug delivery, is presented. Finally, the conclusions and potential research prospective in future are proposed.