Design and application of anti-swelling conductive hydrogels

Hydrogel， a soft material composed of polymers with a three-dimensional network structure， has been widely used in fields such as environmental engineering and biomedicine due to its excellent flexibility， elasticity， high water absorption， biocompatibility， and similarity to biological tissues. Conductive hydrogels also have excellent electrical conductivity compared to traditional hydrogels， which makes them show great potential in emerging fields such as remote health monitoring， human motion detection， electronic skin， human-machine interface and soft robotics. Therefore， in recent years， efforts have been made to develop conductive hydrogels with a variety of properties and explore their applications in various fields. Currently， conductive hydrogels could be classified into electronically conductive hydrogels and ionically conductive hydrogels according to the transmission medium. Usually， conductive hydrogels can be prepared by doping conductive materials into the hydrogel matrix. However， with the continuous deepening of the research on hydrogels， the performance requirements of conductive hydrogels have been increasing， especially the anti-swelling properties of hydrogels. Unwanted swelling in the liquid-phase environment leads to a decrease in the hydrogel’s mechanical properties， electrical conductivity， and is accompanied by a distortion of the sensing signal. Therefore， there is an urgent need to prepare conductive hydrogels with both good electrical conductivity and swelling resistance. In this review， firstly， the preparation methods of different types of conductive hydrogels are discussed. Secondly， several strategies for constructing swelling-resistant conductive hydrogels are discussed， including supramolecular hydrogels， dual-network hydrogels， and so on. Finally， the main application areas of anti-swelling conductive hydrogels are presented.