<p>Ionic actuators with capability of electro-mechanical transduction are emerging as a useful platform for artificial intelligence and modern medical instruments. However, the insufficient ion transport inside material interfaces usually leads to limited energy transduction efficiency and energy density of actuators. Here, we report a polyrotaxane interface with adjustable ion transport based on sliding-ring effect for highly-efficient ionic actuators. The switch status of ion channels is synchronous with actuation strains, and energy barrier of interfacial ion transfer is reduced. As a result, the electro-mechanical transduction efficiency of actuators gets significantly improved. The as-delivered energy density of devices is stronger than that of mammalian skeletal muscle. Based on the high actuation performances, we demonstrate a fiber-shape soft actuator that can be directly injected into biological tissue just using syringe. The injectable actuator is promising for surgical navigation and physiological monitoring.</p>