MEMS sensors for density–viscosity sensing in a low-flow microfluidic environment

Technologies based on micro electro mechanical systems (MEMS) present advantages for downhole oilfield applications since they enable the fabrication of small sensors with fast response times. Furthermore, by incorporating MEMS sensors in a microfluidic environment it would be possible to make representative measurements of fluid properties with a sample volume of no more than 1 μL and flow rates on the order of 1 μL per minute. Here, we fabricate a set of resonating beams with millimetre-scale lengths and micron-scale cross-sections to demonstrate the feasibility of resonance measurements with three different techniques. In addition, we demonstrate how the quality factor and resonance frequency can be measured to calculate the fluid viscosity and density. The effect of flow rate on the sensor is shown to be minimal in microfluidic channels, presumably due to the small cross-sectional area of the beams. These sensors are compatible with the high pressure environments found downhole.