Vanadium oxide thermal microsensor integrated in a microfluidic chip for detecting cholesterol and glucose concentrations

A highly sensitive thermal measurement device based on a vanadium oxide (VOx) microthermistor is developed for detecting biological molecules based on enzymatic reactions. The measurement principle of the VOx thermistor relies on the temperature dependence of its electrical resistance owing to the heat generation of enzymatic reactions. The device comprises a microfluidic channel and chambers, and VOx thermistors on a suspended Si3N4 membrane for thermal insulation. The enzyme is immobilized in silica gel on the sensor. The temperature coefficient of the resistance of the fabricated VOx thermistor is -1.3 %/K. The fabricated device has a temperature resolution of 0.30 mK/aeHz and a temperature response of 4.9 mV/K. Thermal measurements of cholesterol and glucose are demonstrated using the heat production caused by enzymatic reactions. The detectable concentrations of glucose and cholesterol were 30 and 15 A mu M/aeHz, respectively.