Design and Implementation of Injection Locked Oscillator Biosensors

This paper presents the design and the implementation of a Lab-on-Chip biosensor, based on injection locked oscillators (ILO) integrated on a BiCMOS SiGe technology, dedicated to the analysis of biological cells by dielectric spectroscopy at microwave frequencies. The proposed circuit is able to evaluate the dielectric response of suspended cells circulating in a microfluidic channel. Under these conditions, a sensing accuracy of a few attoF is necessary to discriminate differences between cells, which in the case of oscillators in free running frequency would require to be able to generate variations of the oscillation frequency of the order of 10 kHz in the vicinity of 5 GHz. With the proposed biosensor, post layout simulations show that it should be possible to measure effects of 10 attoF capacitive variation. Hence, the architecture of injection locked oscillators may prove to be the much more relevant approach at the price of a total current consumption of 37 mA from a 2.5 V supply voltage.