Resistive heaters for fuel cells

A thermally efficient resistive heater assembly ( 10 ) for heating a source substance for generation of gas has a chamber ( 100 ) for containing the source substance, a thin resistive heating element ( 40 ) suspended across an aperture ( 110 ) and disposed for immersion in the source substance, and conductive traces ( 50 ) electrically coupled to the thin resistive heating element ( 40 ). The resistive heater assembly may be fabricated by a method including (S10) providing a first substrate layer ( 20 ); ( S20 ) bonding to it a second substrate layer ( 30 ), the second substrate layer bearing the resistive heating element ( 40 ) and conductive traces ( 50 ); (S40) bonding to that an optional hydrophobic layer (60) if necessary; and (S50) bonding to the previous layer a top layer (70). At least one of the layers may include manifolding (80) for the gas. All or part of the fabrication method may be performed as a reel-to-reel process.