Gas-liquid crossing flow in microchannel and its application to gas analysis microchip

We developed a novel microchannel structure comprised of deep/shallow/deep tri-channels. Each end of the channel was split into three, and supplying and taking of fluids to/from the channels was possible. Aqueous solution tended to fill the shallow channel because of the capillary force. Thus, by introducing gas/liquid/gas from one end of the channel, stable laminar three-phase flow was formed throughout the channel. We then introduced liquid/gas/liquid to the channels. The flow became turbulent near the confluence, and settled into a gas/liquid/gas laminar profile downstream. The channel-design and flow rates were optimized to form this gas-liquid crossing flow continuously. The gas-liquid crossing flow was useful in micro-analysis and synthesis, because efficient gas-liquid contact at the turbulence promote extraction and reaction, and spontaneous separation of the two phases enabled post processes (e.g. detection). The crossing flows were also formed in other microchannel-structures like shallow/deep/shallow tri-channels and deep/shallow dual channels. A sensor for low-concentration ammonia gas, by using this structure, was also reported in this paper.