Thermoelectric microfluidic sensor for bio-chemical applications

Abstract

A thermoelectric microfluidic sensor (TMS) was developed for characterizing biochemical reactions. The device consists of a 100μm deep microfluidic channel with a Bi/Sb thin-film thermopile attached to its bottom surface. The thermopile has a Seebeck coefficient of ∼7μV(mK)−1 and excellent rejection of common mode thermal signals. The design and geometry of the microfluidic device and thermopile in combination with hydrodynamic fluid focusing facilitates the detection of small dynamic temperature changes in the order of 10−4K without the control of ambient temperature or the thermopile reference junction temperature. Response of the thermopile for interaction of water with various concentrations of ethanol was studied to demonstrate the operation of the sensor. CoventorWare® simulations were performed to demonstrate the hydrodynamic focusing effect and the extent of mixing for different device flow rates. The device has the sensitivity of 0.045V-sJ−1 when known quantities of energy are applied to a nichrome heater incorporated on the inner side of the microfluidic sensor bottom channel wall, while continuously injecting deionized (DI) water. A low ethanol sample volume of 5μL is used in the microfluidic device. Effects of flow rates on the ethanol response were characterized. Results showed an increased ethanol response with a decrease in the relative inlet flow rates.