Interfacial engineering of liquid metal nanoparticles for the fabrication of conductive hydrogels: A review

Gallium-based liquid metals (LMs), especially their nanoparticle forms, have emerged as attractive soft fillers for the fabrication of conductive hydrogels owing to their remarkable combination of conductivity, fluidity and biocompatibility. Unfortunately, the large cohesion, high density and low viscosity of these LM nanoparticles (LMNPs) result in poor compatibility with polymer matrixes, making it hard to construct stable LMNPs-based conductive hydrogels. Herein, the interfacial engineering strategies regarding stabilizing LMNPs within hydrogels are briefly reviewed. The fundamental theories about interfacial engineering of LMNPs are firstly discussed. Then, a variety of interfacial stabilizers involved in encapsulating LMNPs and fabricating conductive hydrogels are introduced, highlighting on their interfacial regulating mechanisms. Furthermore, the versatile applications of the resultant LMNPs-based conductive hydrogels including personal healthcare and motion detection, human–machine interfaces, electromagnetic interference (EMI) shielding, etc., are separately described, illustrating their wide range of uses. Finally, the current challenges and future perspectives of these hydrogels are proposed.