Measurement of thermal properties of microfluidic samples using laser point heating thermometry

This work introduces a novel method to measure the thermal conductivity, diffusivity, and heat capacity of a microfluidic sample having a small-volume of the order of 1 μl. The method is based on a new concept named laser point heating thermometry (LPHT). The method employs point heating of a thermocouple tip using a focused laser beam. As the suggested scheme utilizes external optical heating of a temperature probe, a relatively large amount of heat can be generated at a localized spot. Furthermore, the temperature of the heated spot can be effectively monitored from thermoelectric potential without undesirable electrical interference in the heating and sensing circuitry. In addition to the thermal-property measurement, this simultaneous point heating and point sensing technique can be employed in a variety of thermal-sensing applications including velocity and motion measurement.