SBIR Phase II: An Innovative Normal Stress Sensor System for Complete Characterization of Polymer Shear Flow Properties

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This Small Business Innovation Research (SBIR) Phase II project will address several technical improvements needed for successful commercialization of a novel MEMS sensor plate containing monolithic miniature capacitive pressure sensors. As shown in Phase I, the sensor plate can be used to accurately measure the first (N1) and second (N2) normal stress differences, which are important nonlinear elastic flow properties of various classes of viscoelastic liquids. In Phase II, sensor packaging and lead transfer to the sensors will be made suitable for high volume, high quality manufacturing of sensor plates. One version will be optimized for measurements at lower pressures and another version optimized for measurements on molten commercial thermoplastics at higher temperatures and pressures. The latter version of the sensor plate will be smaller in diameter to make possible measurements on smaller samples at higher shear rates, and will contain miniature temperature sensors that will enable accurate compensation for changes in sensor calibration constant with temperature. Improvements will be tested with a wide variety of commercial polymer systems and other important classes of viscoelastic liquids. This novel sensor plate will meet the critical market need for an inexpensive instrument for fully characterizing shear flow properties of molten thermoplastics. The competing alternative technology, the force rebalance transducer (FRT) is expensive and works best with large samples. It is simpler/less expensive to adapt a sensor plate rather than a transducer to existing rheometers. Hence the sensor plate has significant commercial potential to satisfy pent-up demand for an inexpensive way to upgrade rheometers to allow flow elasticity measurements.