Fig. 1

Osmosis-based reversible actuation: from plant cell to a tendril-like soft robot. a, b Stomata guard cells in a flaccid and b turgid state: schematic and optical images of Tradescantia zebrina leaves (courtesy of Andrea Degl’Innocenti). Scale bars: 10 µm. c, d Cyclic osmoregulation (schematic) c for plant cell and d for our osmotic actuator. The concentration of ions (osmolyte) was controlled in the electroactive control unit through the reversible immobilization on the surface of electrodes, as driven by an input voltage (ions are released to the fluid bulk upon short-circuiting). Ion concentration modulation drives the water flux as in plant cells, and modulates the soft effector stiffness. e Passiflora caerulea tendril reaching and anchoring to an external support. Scale bars: 5 mm main image, 0.5 mm detail. f Artificial tendril actuation (schematic). g Tendril-like soft robot based on the osmotic actuator (schematic)