CMOS Bio-MEMS葡萄糖微感測器

Abstract

This study uses the standard TSMC 0.35 μm 2P4M CMOS Bio-MEMS process to produce a glucose biosensor integrated with a sensing circuit on the chip. The glucose biosensor contains an inter-digitized electrode structure and an oscillator circuit. In the sensing structure we use self-assembled monolayer to modify polymer 11-mercaptoundecanoic acid (11-MUA) on the gold surface. The head group of 11-MUA is sulfur, and the functional groups is carboxyl (-COOH). Because there is a strong force between sulfur and gold, 11-MUA is adsorbed on the surface of the gold layer. The carboxyl end of 11-MUA adsorbs glucose oxidase (GOD), so 11-MUA is a bridge between the GOD and the gold layer. The sensing layer GOD on the gold surface adsorbs the glucose due to it have a high degree of specificity between GOD and glucose. After the GOD combines with glucose, the capacitance of the sensor produces a change due to the dielectrical change. We design an oscillator circuit to convert the capacitance variation into the output frequency. The total area of the sensor chip is about 1.6 × 1.8 mm2. A large sensing area is adopted to increase the signal amplitude. The output frequency is measured by the spectrum analyzer. According to the experimental results, the output frequency increases from 10.402 MHz to 23.715 MHz as the glucose concentration increases from 1 mM to 10 mM. The sensitivity of sensor is about 1.3 MHz/mM.