Lucas123 writes: "The Rabbit Proto is a new 3D printer attachment that can be added to a RepRap printer to create circuitry right alongside an existing thermoplastic extruder. While still in prototype, the printer head is expected to ship this summer. The creators of the Rabbit Proto, a group of Standford graduate students, have already printed working prototypes, such as a game controller. So far, the syringe-like printer head has used silver-filled silicon to create circuitry, but the engineers are now working with conductive inks made with graphite. The Rabbit Proto head unit can be pre-ordered for $350, or you can purchase a fully-assembled RepRap 3D printer with the Rabbit Proto head for $2,499."