Figure 3: Robustness and multiple responsiveness of the actuator.

(a) Adaptive movement of a PILTf₂N/C-pillar[5]arene membrane (1 mm × 20 mm × 30 μm) placed in acetone vapour (24 kPa, 20 °C, left) and then back in air (right); the membrane was immersed in liquid nitrogen (2 h), followed by annealing (150 °C, 24 h) and high-pressure pressing at 100 MPa for 24 h. (b) The same actuation experiment after hydrothermal processing the membrane in water (200 °C, 24 h). Here the membrane is black owing to its partly carbonaceous nature. (c) Motion of a membrane-coated human hair in acetone vapour and then back in air. (d) The reversible closing and opening of a star-shaped membrane actuator ‘flower’ upon switching the humidity between 50 and 90% at 20 °C; here the top surface of the membrane was stained red while the bottom surface retains the original light yellow colour; inserted number is the relative humidity; scale bar, 1 cm.