Stimuli-responsive hydrogel actuators have promising applications in various fields. However, the typical hydrogel actuation relies on the swelling and de-swelling process caused by osmotic-pressure changes, which is slow and normally requires the presence of water environment. Herein, we report a light-powered in-air hydrogel actuator with remarkable performances, including ultrafast motion speed (up to 1.6 m/s), rapid response (as fast as 800 ms) and high jumping height (~15 cm). The hydrogel is operated based on a fundamentally different mechanism that harnesses the synergetic interactions between the binary constituent parts, i.e. the elasticity of the poly(sodium acrylate) hydrogel, and the bubble caused by the photothermal effect of the embedded magnetic iron oxide nanoparticles. The current hydrogel actuator exhibits controlled motion velocity and direction, making it promising for a wide range of mobile robotics, soft robotics, sensors, controlled drug delivery and other miniature device applications.

Peritumoral subcutaneous injection has been highly envisioned as an efficient yet low‐risk administration of photothermal agents for superficial tumor photothermal therapy. However, obstructed by complex subcutaneous tissue, the delivery of injected photothermal agents to the specific tumor remains a critical issue. Herein, the study reports a polydopamine (PDA)‐encapsulated spherical core/shell nanomotor with fluorescent indocyanine green (ICG) immobilized on its PDA shell. Upon the first near‐infrared (NIR‐I) irradiation, this motor can generate favorable photothermal heat, and meantime, emit a robust ICG fluorescence in the second near‐infrared window (NIR‐II). The heat turns the motor into an active photothermal agent able to perform thermophoretic propulsion along the irradiation direction in subcutaneous tissue, while the ICG fluorescence can direct the subcutaneous propulsion of motors toward specific tumor through real‐time NIR‐II imaging. These functions endow the motor with the ability of moving to tumor after being injected at peritumoral site, enabling an enhanced photothermal therapy (PTT). The results demonstrated herein suggest an integrated nanorobotic tool for the superficial PTT using peritumoral administration, highlighting an NIR‐II imaging‐directed subcutaneous propulsion.