Fig. 2.

Actuation performance of the single-layer membrane. a Adaptive actuation movement of a PFSA membrane (5 mm × 15 mm × 75 µm) in response to ethanol vapor sorption and desorption (the vapor is from the left side of the PFSA membrane). b Plots of curvature against time (inset: a schematic of the curvature calculation). The insert image is the actuation curvatures and response time of a 75 μm PFSA film under different ethanol vapor concentrations. c Plots of the reversible deformation of the 75 µm film upon cyclic exposure to a 15% ethanol concentration vapor (8000 cycles without obvious fatigue). d Time-dependent ATR–infrared spectra of film saturated by exposing in ethanol vapor for 10 s (bottom to top: 0–12 s after exposing in air)