I was thinking if the dots need individual actuators. I'm old enough to remember dot-matrix printers; take the print head but put slightly beefier pins on it, move it left and right and use it to push metal spheres up in a hour-glass shaped cavity, with springy walls in the center section.
Obvious problems: how do you reset the spheres? And wear issues.
Edit: You could replace the hourglass throat with a plug valve (shared between pins). Print head comes along, turns the valve open, pushes the necessary balls up, closes valve, moves to next column. Needs more mechanics per cell, though.
I was thinking if the dots need individual actuators. I'm old enough to remember dot-matrix printers; take the print head but put slightly beefier pins on it, move it left and right and use it to push metal spheres up in a hour-glass shaped cavity, with springy walls in the center section.
Obvious problems: how do you reset the spheres? And wear issues.
Edit: You could replace the hourglass throat with a plug valve (shared between pins). Print head comes along, turns the valve open, pushes the necessary balls up, closes valve, moves to next column. Needs more mechanics per cell, though.