a) S 2p XPS signals for VHF 2 SAMs. b) Optical images of water droplets on surfaces of DHA 1 (left) and VHF 2 (right) SAMs, and revers- ible wettability transitions as a function of alternating thermal treatment and UV irradiation. c) Optical transmission spectra of rGO films with a series of film thicknesses. Inset, a ≈7 nm-thick rGO film transferred onto quartz for transmission measurement. d) Optical and AFM images of rGO films transferred onto bottom electrodes. The ultrathin flexible rGO film follows the topography of the electrode patterns and ensures a good contact to the SAMs at the bottom of the microholes. The texture of the film is clearly visible.