A Novel Liquid Metal and Microfluidic Based Temperature Sensor

We present a novel liquid metal based temperature sensor. This sensor utilizes thermal expansion property when temperature changes. The liquid metal (mercury) is used for electrical interconnect between capacitors as it expands through a microfluidic channel. Among various temperature sensing methods, platinum resistive thin film devices [1] and acoustic wave devices [2] are commonly being used. The platinum thin film based device utilizes a unique property that the resistant of the thin film changes with respect to temperature variation. A complete sensor can be realized in a balanced wheat stone bridge. When the temperature changes, the resistance of the thin film changes correspondingly and the bridge is no longer balanced. There is a current flow through the bridge upon the amount of temperature variation. However, the current brings a self-heating problem, which negatively affects the performance. On the other hand, the acoustic wave device utilizes a property that a resonance frequency shifts per temperature variation. There are many difficulties in calibrating this device and, in liquid environment, there is a significant drop of q factor [3], which decreases the sensitivity of the sensor. Our new device can overcome many difficulties described above.