High-precision digital microflow controllers using fluidic digital-to-analog converters composed of binary-weighted flow resistors

This paper presents digital microflow controllers (DMFC), where a fluidic digital-to-analog converter (DAC) is used to achieve high-linearity and fine-levels in flow-rate control for applications to precise biomedical dosing systems. The fluidic DAC, composed of binary-weighted flow resistance, is designed to control the flow-rate based on the ratio of the flow resistance to achieve finer flow-rate levels. The binary-weighted flow resistance has been specified by a serial or a parallel connection of an identical flow resistor to improve the linearity of the flow-rate control by making the flow-resistance ratio insensitive to the size errors of flow resistors in micromachining process. We have designed and fabricated three types of 4-digit DMFC: Prototype S and P with serial and the parallel combinations of an identical flow resistor and Prototype V with width-varied flow resistors. In the experimental study, we perform static DMFC tests at forward and backward flow conditions as well as dynamic DMFC tests at pulsating flow conditions. The present DMFC shows the nonlinearity of 5.0% and finer flow-rate levels of 16(2/sup N/) for 4(N) digital valves. From the measured flow-rate deviation due to micromachining errors, Prototype S and P show 27.2% and 27.6% of the deviation measured from Prototype V, respectively; thus, verifying that Prototype S and P are less sensitive to the micromachining errors than Prototype V.