The VROC® sensor obtains a viscosity reading by measuring the pressure drop as a test liquid flows through a flow channel. This is a well-known application of rheometry principles (K. Walters, Rheometry, Chapman and Hall, London, 1975).
As the test liquid is forced to flow through the flow channel of the sensor, pressure is measured at positions of increasing distance from the inlet. The slope of the straight line in the plot of the pressure vs. sensor position (as shown in the graph) is proportional to the viscosity. See the principle for more information.
RheoSense took this principle and created a dynamic micro-sample viscometer by adding microfluidics, and reducing the size of the device with MEMS manufacturing. As a result, VROC® technology offers capabilities that are well beyond the limits of conventional viscometers.