A generally toroidal counterflow heat exchanger is the main element of a combustor
that operates at a micro scale. The combustor includes a central combustion region
with openings to a reactant gas channel and an exhaust gas channel. The reactant
channel and exhaust channels are coiled around each other in a spiral configuration
that reduces heat loss. An electric current microgenerator is similar and also
includes a thermoelectric active wall composed of n-type and p-type thermoelectric
elements as part of a channel wall of the microcombustor. The thermoelectric active
wall includes fins configured to increase the temperature differential across the
thermoelectric elements relative to the temperature difference between the thermoelectric
elements and the reactant and exhaust gases. A method of monolithically fabricating
such microdevices by electrodepositing multiple layers of material is also provided.