An electronic pen for interacting with a surface. The pen comprises a cartridge having a nib for contacting the surface, a capacitive force sensor cooperating with said cartridge for sensing a nib force transmitted axially through the cartridge, and a processor configured to generate force data indicative of a force detected by the force sensor. The capacitive force sensor comprises: a spring having an integral conductive moving plate resiliently biased towards a reference position, a conductive fixed plate and a dielectric separating said plates.