Embedded MEMS-based concentration sensor for fuel cell and biofuel applications

A MEMS-based chemical concentration sensor for monitoring and controlling the methanol to water ratio in a Direct Methanol Fuel Cell (DMFC) is described. This sensor is based on a vacuum packaged resonant microtube and on-chip platinum temperature sensor to measure the density of a fluid. Using the density and temperature output the methanol concentration is determined. The performance of the sensor over temperature, concentration and in the presence of formic acid by-products is examined. Additional test results and applications for other fuels and biofuels are presented including ethanol, ethylene glycol, butanol, gasoline and diesel fuel.