Microchannels for applications in liquid dosing and flow-rate measurement

To investigate the performance of microengineered fluid channels in liquid dosing applications, flow-rate measurements have been performed with various channel geometries in a range from 0.01 to 1000 mu l min-1. An optical flow-measurement technique has been developed to enhance the measurement range into the desired flow range (10-3 to 1 mu l min-1), and is compared to a standard gravimetric method, which is preferably used for flow rates above 1 mu l min-1. In addition, influences of the temperature-dependent viscosity and effects arising from fluid mechanical characteristics are studied. These influences are also calculated from laminar flow theory and semi-empirical models to obtain a theoretical model. It is found that the theoretical model is able to describe the measurement results well in the whole flow range. The model is implemented on a PC-based system, which measures the pressure drop across the microchannel and the fluid temperature and from 20 to 50 degrees C excellent ag reement is found