Temperature distribution measurement of Au micro-heater in microfluidic channel using IR microscope

The temperature control and measurement of micro-heater in microfluidic devices are very essential in various application fields such as gas sensors, flow sensors and bio-sensors. In this study, the temperature of a micro-heater was measured while applying voltages to micro-heaters with 100 μm width in microfluidic devices using infrared microscope. The Au micro-heater was fabricated onto a sapphire substrate with good infrared transmission. In order to measure the temperature of Au micro-heater from the back side of sapphire substrate using infrared microscope, the adhesion layer was not used during e-beam evaporation. To overcome the poor adhesion force between sapphire substrate and Au thin-film, thermal annealing was carried out at 400°C. This measurement method enables us directly to measure the IR emissivity of Au micro-heater in aqueous media without infrared diffraction, absolution and reflection. Based on the calibration curve, we could measure the real temperature of Au micro-heater with 100 μm width at atmospheric environment and in aqueous media. Consequently, we could measure the temperature range at atmosphere and in DI water. The companion computational fluid dynamics simulation studies showed that the measured temperature of Au micro-heater was in accordance with the simulated results within 5 K in average sense.