Plastic microchannel-microheater chips were fabricated on the basis of imprinting and photolithography/etching techniques. Knowing the temperature-dependent fluorescence lifetime of Rhodamine B in water, the temperature profile of the solution phase in the microchannel in the vicinity of the heater was evaluated by space- and time-resolved fluorescence microspectroscopies. The fabricated chip was then applied to control the thermal phase transition of an aqueous poly(N-isopropylacrylamide) (PNIPAM) solution. PNIPAM particle formation by the phase transition was controlled by both the applied voltage to the heater and the solution-flow rate. The temperature profile showing below or above the phase-transition temperature (i.e., 32 °C) and solution-flow profile in the microchannel were visualized successfully on the basis of the PNIPAM particle formation. The continuous and automated concentration of a hydrophobic solute by the PNIPAM particles produced by the phase transition was also explored under solution-flow conditions by using the fabricated chip.

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