Miniaturized and untethered McKibben muscles based on photothermal-induced gas-liquid transformation

Pneumatic artificial muscles offer continuous movement and flexibility but are hindered in miniaturization by external pumps, valves, and tethers. Here, a light-driven, miniaturized fiber-reinforced artificial muscle is reported that achieves axial elongation and bending via photothermal-induced gas–liquid phase conversion of a low-boiling-point fluid. Using a mold-editing approach, a prepolymer containing nanocarbon and phase-change liquid is UV-cured to form a sealed cylindrical cavity while a PTFE fiber membrane constrains radial expansion to maximize axial actuation. The minimum actuator volume reaches 15.7 mm³ (d = 2 mm, l = 5 mm), smaller than other fiber-reinforced pneumatic actuators. The device is rechargeable by soaking to replenish liquid, and under visible light exhibits efficient expansion, elongation, and programmable bending for tasks such as grasping and crawling in confined spaces.

Wenfei Ai, Kai Hou, Jiaxin Wu, Yue Long, Kai Song