Tough and responsive hydrogels have recently attracted great research interestsfor potential applications in artifical muscles, soft robotics, and actuators,etc. This paper overviews our recent progresses in the design and synthesis ofhydrogels with very high strength and toughness, and actuators based on thesehydrogels. Inorganic nanospheres, nanorods, and nanosheets are exploited asmulti-functional crosslinkers to adsorb or bond with hydrophilic chains, leadingto hydrogels with very high strength, toughness, fatigue resistance, and/orself-healing. Introduction of functional groups including ionic monomers andamino groups results in hydrogels reponsive to pH, ionic strength and electricfield. Besides, ionoprinting has been used to change local crosslink densitybased on reversible chelating/decomposition of metal ions with functionalgroups. This process is rapid and thus enables reversible and rapid actuation ofhydrogel devices. Our studies will further aim to develop sophiscated devices byassembling hydrogel actuators.