A 40-GHz Fully-Integrated CMOS-Based Biosensor Circuit with an On-Chip Vector Network Analyzer for Circulating Tumor Cells Analysis

This paper presents a 40-GHz fully-integrated CMOS biosensing system with an on-chip vector network analyzer (VNA) and a detection area for circulating tumor cells (CTCs) analysis. A first-stage mixer is configurated to enable the operation at 40 GHz, which has the capability of analyzing CTCs highly sensitively owing to γ dispersion. To confirm the effectiveness of the proposed system, a test chip was fabricated with 65-nm CMOS technology, and measured by adding magnetic beads at different concentrations on the detection area. The measurement result demonstrated that the proposed circuit could characterize beads even at a low concentration of 10 beads/μL. Additionally, it was observed it could improve the sensitivity and limit of detection (LOD) compared with the previous 1.4-GHz-system: from 0.0385 dB/(beads/μL) to 0.0745 dB/(beads/μL) in sensitivity and from 8.3 to 3.3 beads/μL in LOD. It can be estimated that this biosensing circuit can detect a lower concentration of a CTCs sample named H1976 cells than 50 cells/μL. Therefore, the proposed circuit has the possibilities to analyze CTCs practically.