CMOS MEMS Hot-Film Thermoelectronic Flow Sensor

In this article, we present a complementary metal-oxide semiconductor microelectromechanical system (CMOS MEMS) thermoelectronic flow sensor and discuss the advantages of employing anemometric and calorimetric transduction principles simultaneously. This readout concept exploits the fact that anemometric flow sensors take advantage of the maximum temperature generated within the device and, thus, are provided with the maximum flow sensitivity, while calorimetric flow sensors have the temperature sensing elements placed away from this maximum temperature region and, thus, are intrinsically less sensitive. At the same time, fluid flow direction discrimination in bidirectional flow sensors can be achieved by simply looking at the polarity of the differential signal coming from the temperature sensors placed aside the heating element. We also show that thermoelectronic flow sensors can benefit by having temperature sensors formed by an array of diodes to further enhance the device sensitivity. Although we apply these concepts to a sensor with a nonoptimum design and lacking any support electronics (e.g., filters, amplifiers, constant temperature driving circuitry, etc.), results are among the best ever reported in literature (including non-CMOS technologies), thus showing the high potential of our technology.