A MEMS flow sensor comprising: a body having a first semiconductor substrate and a second substrate bonded together, wherein the second substrate is one of: a semiconductor substrate and a glass substrate; a micro flow channel etched in the body and having an etched inlet opening at a first face of the body and an etched outlet opening at an opposite face of the body , the micro flow channel extending through the body from the etched inlet opening at the first face to the etched outlet opening at the opposite face; a film heater integral with the body and associated with the flow channel to heat fluid flowing through the flow channel ; at least one film temperature sensor integral with the body and associated with the flow channel in a position spaced along the flow channel from the film heater , the at least one film temperature sensor operative to sense the temperature of fluid flowing through the flow channel , electronic circuitry integrated in the body and electrically connected to the film heater and the at least one film temperature sensor are operative to provide a signal representative of the rate of flow of a fluid flowing through the flow channel based at least in part on the temperature of fluid flowing through the flow channel sensed by the at least one film temperature sensor , and characterised in that the film heater and the at least one film temperature sensor form a first loop portion on the first semiconductor substrate and a second loop portion on the second substrate, and wherein the first loop portion and the second loop portion form a complete coil around the inside of the flow channel . a body having a first semiconductor substrate and a second substrate bonded together, wherein the second substrate is one of: a semiconductor substrate and a glass substrate; a micro flow channel etched in the body and having an etched inlet opening at a first face of the body and an etched outlet opening at an opposite face of the body , the micro flow channel extending through the body from the etched inlet opening at the first face to the etched outlet opening at the opposite face; a film heater integral with the body and associated with the flow channel to heat fluid flowing through the flow channel ; at least one film temperature sensor integral with the body and associated with the flow channel in a position spaced along the flow channel from the film heater , the at least one film temperature sensor operative to sense the temperature of fluid flowing through the flow channel , electronic circuitry integrated in the body and electrically connected to the film heater and the at least one film temperature sensor are operative to provide a signal representative of the rate of flow of a fluid flowing through the flow channel based at least in part on the temperature of fluid flowing through the flow channel sensed by the at least one film temperature sensor , and characterised in that the film heater and the at least one film temperature sensor form a first loop portion on the first semiconductor substrate and a second loop portion on the second substrate, and wherein the first loop portion and the second loop portion form a complete coil around the inside of the flow channel . <EOS>