A Built-In Temperature Sensor in an Integrated Microheater

Chip-based microheaters have been widely used in many applications, including gas sensors, flow meters, mass sensors, and polymerase chain reaction chambers, where accurate monitoring of temperature is critical. The temperature measurement is conventionally done with the aid of a separate sensor, which may add to the cost and inaccuracy. In this paper, a built-in temperature sensing method is provided for the microheaters. The resistor-based microheater relies on Joule heating mechanism and its resistance is dependent upon its own body temperature, implying that the microheater has an inherent temperature sensing mechanism. It is found that an intermittent temperature sampling in the middle of the heating cycle does not disturb the body temperature if the temperature sampling voltage and pulsewidth are sufficiently low and short, respectively. The built-in temperature sensing is attributed to the electrical time constant being few orders of magnitude smaller than the thermal time constant. The temperature estimation results using the built-in method show excellent agreement with the benchmark measurements from an infrared pyrometer.