18. The subassembly of claim 17 wherein the selectively-permeable outer membrane has a surface divided into a plurality of chordal segments, each chordal segment being configured to produce a character segment.
18. The subassembly of claim 17 wherein the selectively-permeable outer membrane has a surface divided into a plurality of chordal segments, each chordal segment being configured to produce a character segment. 19. The subassembly of claim 18 , wherein the programmable rotary actuator is configured to drive the cylindrical, self-inking print roller.