A robot-mounted 3D printing apparatus for extruding multiple reagent compositions, the apparatus comprising: • a detachable 3D printing device, wherein the detachable 3D printing device is a handheld device, comprising a housing comprising: a first reagent container support arrangement which in use receives and supports a first reagent container containing a cell supporting reagent; a second reagent container support arrangement which in use receives and supports a second reagent container containing a light curable reagent; a nozzle (2, 20, 120, 840) connected at a distal end to the housing and comprising a co-extrusion tip comprising at least one aperture, and a first conduit for receiving the first reagent driven out of a proximal end of the first reagent container and directing the first reagent out of the at least one aperture in the co-extrusion tip, and a second conduit for receiving the second reagent driven out of a proximal end of the second reagent container and directing the second reagent out of the at least one aperture in the co-extrusion tip; characterized in that the apparatus further comprises: a power supply; an electric drive train arrangement configured to drive a first reagent piston into a distal end of the first reagent container, and to drive a second reagent piston into a distal end of the second reagent container; an electronic control circuit to control the electric drive train arrangement to control extrusion of the reagents from the first and second reagent containers (8,9); • a multiaxial jointed robot-arm; • a mount attached to one end of the multiaxial jointed arm, wherein the mount is configured to hold the detachable 3D printing device; and wherein the mount is configured to allow loading and replenish of the reagent containers (8, 9). • a detachable 3D printing device, wherein the detachable 3D printing device is a handheld device, comprising a housing comprising: a first reagent container support arrangement which in use receives and supports a first reagent container containing a cell supporting reagent; a second reagent container support arrangement which in use receives and supports a second reagent container containing a light curable reagent; a nozzle (2, 20, 120, 840) connected at a distal end to the housing and comprising a co-extrusion tip comprising at least one aperture, and a first conduit for receiving the first reagent driven out of a proximal end of the first reagent container and directing the first reagent out of the at least one aperture in the co-extrusion tip, and a second conduit for receiving the second reagent driven out of a proximal end of the second reagent container and directing the second reagent out of the at least one aperture in the co-extrusion tip; a first reagent container support arrangement which in use receives and supports a first reagent container containing a cell supporting reagent; a second reagent container support arrangement which in use receives and supports a second reagent container containing a light curable reagent; a nozzle (2, 20, 120, 840) connected at a distal end to the housing and comprising a co-extrusion tip comprising at least one aperture, and a first conduit for receiving the first reagent driven out of a proximal end of the first reagent container and directing the first reagent out of the at least one aperture in the co-extrusion tip, and a second conduit for receiving the second reagent driven out of a proximal end of the second reagent container and directing the second reagent out of the at least one aperture in the co-extrusion tip; a power supply; an electric drive train arrangement configured to drive a first reagent piston into a distal end of the first reagent container, and to drive a second reagent piston into a distal end of the second reagent container; an electronic control circuit to control the electric drive train arrangement to control extrusion of the reagents from the first and second reagent containers (8,9); • a multiaxial jointed robot-arm; • a mount attached to one end of the multiaxial jointed arm, wherein the mount is configured to hold the detachable 3D printing device; and wherein the mount is configured to allow loading and replenish of the reagent containers (8, 9).