A Novel Combined Rheometer and Density Meter Suitable for Integration in Microfluidic Systems

In this contribution we present a combined rheometer and density meter based on two vibrating membranes carrying electrically conductive paths for excitation and readout. The liquid is contained in a 100 mul volume between the rectangularly clamped membranes. The vibration is excited by Lorentz forces arising from a static magnetic field provided by a permanent magnet and the current through the excitation path going back and forth on the vibrating part of the membrane. The sensor element is designed in such a way that the viscous liquid is subjected to shear stress. Additional conductive loops on the membrane perform the sensor readout by means of the induced voltage due to motion in a static magnetic field. The measured frequency response in a range from 500 Hz to 15 kHz allows the determination of the fluid´s mass density and viscosity. This novel sensor design is well suited for miniaturization and the integration in microfluidic platforms.