Micromachined viscosity sensor for real-time polymerization monitoring

This paper reports on low-frequency micromachined viscosity sensors intended for real-time polymerization monitoring. The viscosity sensors consist of micromachined membrane resonators featuring electrothermal excitation and piezoresistive detection of transverse membrane vibrations. In contrast to high-frequency (above 1 MHz) sensors, e.g. thickness-shear mode sensors or Lamb wave sensors, the use of low-frequency (1-20 kHz) resonators for viscosity sensing, which more closely mimics conventional resonant viscometers, is investigated in this work. The viscous fluid loads the membrane resonator and changes the quality factor of its fundamental resonance. The change in the Q-factor is most pronounced in the viscosity range from 10(-3) Pa.s to 1 Pa.s.