The shapes into which sepiomelanin arranges its backbone, alternate-sheet and helix, allows to hypothesize that the black pigments can play different roles in different districts according to their feature. It is to note that reactions involving the radical or the cation site of melanin radical-polarone produces a local carbon hybrid change and determines variations of the strand course in the space. This response to chemical radical attack could determinate abrupt conductivity changes and to indicate a possible chemical switching function of this pigments. On this topic, it was reported that melanins respond to a critical applied field by changing their conductivity and that the nature of response depends on hydration and temperature of sample and on external circuity. It was also reported that the response is a memory and threshold switching.
Melanins exhibits two separate current-voltage characteristics, the on and off state.
Dried samples, kept 30 at 200 C minutes don't switch. Re-hydration and drying at room temperature restore switching properties.