A preferred modular microplasma microchannel reactor device includes a microchannel array arranged with respect to electrodes for generation of plasma and isolated by dielectric from the electrodes. A cover covers a central portion of the microchannel array, while leaving end portions of the microchannel array exposed. A gas inlet and product outlet are arranged to permit flow into, through and out of the microchannel array. Reactor modules of the invention include pluralities of the modular reactor devices. The reactors devices can be arranged by a housing or a frame to be in fluid communication. A system of the invention arranges pluralities of modules. Preferred module housings, frames and reactors include structural features to create alignments and connections. Preferred modules include fans to circulate feedstock and reaction product. Other reactor devices provide plasma actuation for flow.