A very unusual ink-jet printer cartridge, containing explosive ink, has been patented by Qinetiq, the commercial spin-off of the British Ministry of Defence.

The ink is a mixture of very fine aluminium particles, each 1 micrometre in diameter, particles of copper oxide 5 micrometres wide, epoxy varnish and alcohol. The ink is stable in liquid form, making it safe to print onto conventional paper, but forms an explosive fuse once dry.

An engineer can easily sketch out a printable fuse using computer imaging software, modifying the delay in milliseconds by changing the length, thickness and pattern of the line on the paper.

The ink can then be printed between a small strip of metal and a larger patch of explosive ink. Feeding a current through the metal strip makes it hot enough to ignite the fuse, which burns until it reaches the explosive patch. This explosion can then trigger the detonation of a much larger amount of explosives.

Qinetiq suggests printed fuses could be used for precisely controlling fireworks, triggering vehicle air bags or for conventional munitions. Ganging hundreds or thousands of fuses together could even make a miniature rocket engine capable of precisely adjusting the orbital position of a spacecraft, the company says.