Dielectrophoresis-assisted 65-GHz LC-oscillator array CMOS chips for label-free and sensitive detection of microorganism cells

In this paper, we propose a miniature, sensitive, and label-free method for detecting Escherichia coli (E. coli) and Saccharomyces cerevisiae (yeast) by using a complementary metal-oxide-semiconductor (CMOS) chip with die-lectrophoresis (DEP)-assisted LC-oscillator arrays. Each of the 62 x 24 arrayed sensor elements on the CMOS chip comprises a 65-GHz LC oscillator that senses the dielectric change due to the presence of the microorganisms. Given the non-uniform sensitivity of the LC oscillator, the DEP electrodes fabricated to be placed at the most sensitive position of the LC-oscillator were used to collect microorganisms and thereby enhance the measurement sensitivity. The AC electric field of DEP above 2 MHz interferes with the 65-GHz LC oscillator circuit in the designated vicinity. With appropriate DEP settings, each sensor element can achieve a limit of detection of two E. coli cells or one yeast cell. Quantitative enumeration reaches a single-cell resolution at small microorganism numbers. The results of this study confirmed that the novel approach of combining DEP technique and LC-oscillator array can perform high-sensitivity detection of microorganisms. Further, the realization of large-scale paralleled measurement makes the proposed CMOS biosensor a potential candidate as a rapid and low-cost lab-on-a-chip sensor for food inspection and clinical diagnosis.