A carbon interdigitated electrode can be patterned by scanning the laser beam on  a resin material such as polyimide, where the the irradiated area of a polyimide film is converted into conductive carbon. Movie 1 shows a direct laser writing of a conductive carbon interdigitated electrode on a polyimide film by galvano- scanning of a blue laser beam.

Because a carbon layer formed by this method has a porous structure and the large surface area,  a carbon interdigitated  electrode can be applied to  an in-plane micro-supercapacitor (electric double layer capacitor) and a modifier electrode for various types of sensors.

【Movie１】Laser direct writing of a carbon interdigitated electrode by blue laser scanning on a polyimide film.

Graphene is expected to be a next-generation electronic material and is being investigated in various ways. Graphene oxide (GO), a partially oxidized surface structure of graphene sheets, is dispersible in water and polar solvents, enabling a printable film formation process. GO is photo-reduced to conductive reduced graphene oxide (rGO). Therefore, rGO/GO micro interdigitated electrodes can be obtained by using the direct laser writing method.

GO works as a proton conductor due to the presence of hydroxyl and carboxyl groups on the surface of the graphene sheet. This property can be applied to a humidity sensor by utilizing the change in resistance of a rGO/GO micro-interdigitated electrode (Fig.3).

GO has many functional groups on the surface of graphene sheets, and so chemical modification of these groups is expected to lead to various sensor applications.

【Movie ２】Humidity sensor using a rGO/GO micro-interdigitated electrode working on a smartphone.