An apparatus for selectively depositing a particulate material onto a substrate, comprising: a material ejector body defining a nozzle and a microchannel region therein; a microchannel disposed within said microchannel region, said microchannel comprising wall structures defining a nozzle profile; a particulate inlet channel disposed within said nozzle; at least one electrostatic particulate transport subsystem disposed with said particulate inlet channel; a particulate reservoir communicatively coupled to said particulate inlet channel for delivery of particulate material; and a propellant source communicatively coupled to said nozzle; characterized in that said particulate inlet channel is substantially uniformly spaced apart from at least first and second opposite surfaces of said nozzle to thereby define substantially symmetrical first and second flow regions (71a, 71b) between said particulate inlet channel and said at least two opposite surfaces of said nozzle and said particulate inlet channel is disposed relative to said propellant source and within said nozzle such that propellant provided by said propellant source may flow substantially uniformly past said particulate inlet channel within said first and second flow regions; whereby particulate material may be provided by said particulate reservoir to said particulate inlet channel, said particulate material metered by said electrostatic particulate transport subsystem and transported from said electrostatic particulate transport subsystem by propellant flowing substantially uniformly past said particulate inlet channel within said first and second flow regions, and carried by said propellant to exit said material ejector body through said microchannel region toward said substrate. a material ejector body defining a nozzle and a microchannel region therein; a microchannel disposed within said microchannel region, said microchannel comprising wall structures defining a nozzle profile; a particulate inlet channel disposed within said nozzle; at least one electrostatic particulate transport subsystem disposed with said particulate inlet channel; a particulate reservoir communicatively coupled to said particulate inlet channel for delivery of particulate material; and a propellant source communicatively coupled to said nozzle; characterized in that said particulate inlet channel is substantially uniformly spaced apart from at least first and second opposite surfaces of said nozzle to thereby define substantially symmetrical first and second flow regions (71a, 71b) between said particulate inlet channel and said at least two opposite surfaces of said nozzle and said particulate inlet channel is disposed relative to said propellant source and within said nozzle such that propellant provided by said propellant source may flow substantially uniformly past said particulate inlet channel within said first and second flow regions; whereby particulate material may be provided by said particulate reservoir to said particulate inlet channel, said particulate material metered by said electrostatic particulate transport subsystem and transported from said electrostatic particulate transport subsystem by propellant flowing substantially uniformly past said particulate inlet channel within said first and second flow regions, and carried by said propellant to exit said material ejector body through said microchannel region toward said substrate.