Liquid Thermocouple Using Thermoelectric Ionic Liquids

This article reports on the fabrication and evaluation of a novel liquid thermocouple. The sensor is composed of two microfluidic reservoirs, a heat stage, and three electrodes. One reservoir contains a polymer electrolyte-polyethylene glycol-NaOH (PEG-NaOH)-and the other an iodine aqueous solution. The ionic liquids are electrically connected via a bridging electrode deposited over the heat stage. Varying the temperature of the heat stage causes a temperature distribution across the liquids, which changes the total thermoelectric voltage across the two ionic liquids. The device is fabricated using conventional microfabrication techniques, and the thermoelectric power response and sensitivity are evaluated. The output voltage of the thermocouple increases linearly with the input temperature. The liquid thermocouple has a Seebeck coefficient of 10.6 mV/K and an estimated temperature resolution of 8.94 mK. The ease of fabrication and the characterization results of this ionic liquid-based thermocouple show that it has the potential for integration in microfluidics-based applications such as biosensing and lab-on-a-chip.