Theoretical and experimental studies of microflows in silicon microchannels

The determination of fluid flows in silicon microchannels is important for the design of microfluidic systems. In this paper, experimental investigations on the characteristics of low fluid flows (few μl h− 1) in silicon trapezoidal microchannels (21 μm in depth, length and width ranging from 200 to 440 mm and 58 to 267 μm, respectively) are presented. The test-devices have been fabricated using micromachining technologies. A double KOH etching process has been used to achieve microchannels in (100)-oriented silicon wafers as well as deep in-plane cavities used for capillary connections. Silicon has been finally anodically bonded on Pyrex substrates. The experimental set-up, based on the measurement of a differential pressure and a liquid–air interface displacement in a gauged tube, is fully detailed in terms of fluidic connections and measurement principle. The experimental results are in good agreement with the Navier–Stokes theory, solved by a simple iterative method. However, finite element modelling has been used to study complex 3D problems that were found in the devices and the experimental set-up. Finally, we propose abacuses for three different channel cross-sections that may be used to easily compute the flow in a microchannel.