Contactless rotational concentric microviscometer

We investigated the feasibility of a concentric rotational microviscometer which is actuated remotely. This type of sensor might find application in vivo as a passive implant. The heart of the sensor is a cylindrical rotor, actuated from a distance of up to 10 mm, that rotates in the viscous liquid. Its angular position is remotely measured using two Hall effect sensors. The advantage of our system is the simplicity of the principle and the miniaturization potential as well as the small sample volume required (5 mu L). In the low viscosity range, the limit of Taylor-Couette instable flow is reached. In this work we present both a theoretical and a practical approach to the limit of the Taylor-Couette flow that is observed at low viscosities (3-4 mPa s). Despite this effect, we show that viscosity measurements with this non-linear behavior are still possible. The observed sensor stability over 14 days is better than +/-0.5% for liquids ranging from 1.35 to 17.25 mPa s. (C) 2011 Elsevier B.V. All rights reserved.