A Closed-Loop Mass Flow Controller Based on Static Solid-State Devices

A mass flow controller, based on an integrated flow sensor and a thermally actuated solid state regulator, is presented. The sensor is a miniaturized differential calorimeter obtained by postprocessing a silicon chip fabricated by a standard microelectronic process. The regulator consists in a microchannel etched into the surface of a silicon substrate and sealed with a glass plate, joined to the silicon die using anodic bonding. Flow regulation is achieved by varying the channel temperature by means of a chromium resistor. The two devices are connected in closed-loop through a low noise--low offset electronic circuit. Experimental data, demonstrating the effectiveness of the flow controller, are presented. Limitations of the proposed approach and possible improvements are discussed.