Figure 2: Actuation of the membrane 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). Note: acetone solvent is stained in blue. (b) Plot of curvature against time for the membrane actuator in (a); on the left: a schematic of how the curvature is calculated. (c) Plot of ‘curvature × thickness’ against time for the membrane actuator in (a) and from literature results (blue triangle) compared with lines of constant actuation speed (Supplementary Fig. 11 and Supplementary Table 1). (d) Plot of the force generated by membrane actuator in (a) against time when the membrane was exposed to acetone vapour (24 kPa, 20 °C) and air alternatively; M is the force that the actuator exerted on the balance; M₀ is the weight of the actuator membrane. On the left: schematic illustration of the experimental force measurement set-up.