We report the first demonstration of combustion-assisted hydrogen production achieved without electrical power input in a MEMS device. The chemical reactor/heat exchanger consists of suspended tubes of low-stress silicon nitride, with integrated slabs of silicon, attached to a silicon substrate. The self-sustained combustion was accomplished after implementation of several improvements over the previous reactor design. These include the integration of composite heater metallizations with improved thermal stability relative to Ti/Pt. In addition, functional passive fluidic stop valves fabricated by deep reactive ion etching and modified with silane coupling agents are integrated in the reactor for catalyst localization. Results from simultaneous combustion (of hydrogen and butane) and ammonia cracking at temperatures up to /spl sim/930/spl deg/C are presented.