Ionic devices based on ion gel. (a) Scheme of the capacitive press sensor based on ion gel. (b) Photographs of cylindrical ion gel capacitive sensor. The gel electrodes were coated with transparent insulating rubber layer PDMS. (c) Capacitance change versus time plot with different press stimuli. (d) Photographs of ion gel-based flexible LED device. (e) Photographs of ion gel-based electroluminescent device, original (left) and after storing (right) in air for 1 month. (f) Photograph of hydrogel-based electroluminescent device after storing in air for 1 day; the device lost uniformity of luminescence as well as flexibility. (g) Ion gel cable in water environment at different temperatures; the ion gel cable was quite stable at such harsh conditions.