Print head for use in a ballistic aerosol marking apparatus

A print head, comprising:

• a substrate having formed therein first and second channels, each said channel having a propellant receiving region, a marking material receiving region, and an exit orifice, each said exit orifice having a width greater than zero micrometers but not exceeding 250 micrometers;
• a material layer disposed over said substrate, said material layer being provided with first and second marking material ports, said first marking material port in communication with the marking material receiving region of said first channel, said second marking material port in communication with the marking material receiving region of said second channel, said material layer further provided with first and second propellant ports, said first propellant port in communication with the propellant receiving region of said first channel, said second propellant port in communication with the propellant receiving region of said second channel;
• such that propellant provided to said propellant receiving region of each said channel may be caused to form a propellant stream travelling through each said channel to and through said exit orifice of each said channel, and marking material provided to each said marking material receiving region may be caused to enter each said propellant stream and imparted with sufficient energy thereby to travel to and through each said exit orifice.