Micromachined oxygen gas sensors for microscopic energy consumption measurement systems

Although the indirect calorimeter is a useful tool, its size and expense mean that it is seldom used in hospitals. Furthermore, its flow-through measurement technique dilutes respiratory variations, so they can only be detected with some form of high-precision instrumentation. This study employs MEMS techniques to develop an oxygen sensor as one part of a microscopic energy consumption measurement system, which measures respiration dynamics in a real time manner. The oxygen sensor comprises a polysilicon resistor and a Li-doped (2 wt%) tin-oxide sensing film attached to a thermally isolated silicon-nitride membrane. The power consumption of the sensor is less than 25 mW at an operating temperature of 150 degrees C. Furthermore, it measures oxygen concentrations between 25 and 85% with a linear output response. These characteristics render the proposed sensor suitable for use within a microscopic energy consumption measurement system in either hospital or homecare environments.